Term
| clinical relevent corollaries of behaviors as all the result of brain function |
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Definition
| 1. disorders of neurological diseases, sensory perception, movement, and cognition are disturbances in brain function; 2. disorders associated with psychiatirc illnesses-feelings, mood, and thought reflect disturbances in brain function |
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Term
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Definition
| specialized for communication, and esp rapid and precise point to point transfer or info in between cells |
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Term
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Definition
| 1. receptive area-includes dendrites which are receptor surfaces and cell bodies; 2. transmission area that includes the axon; 3. synapse area where there is communication between neurons by the release of neurotransmitters |
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Term
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Definition
| 1. sensory neuron-include dorsal root ganglion and almost all conductive portion; 2. motor neurons-more of a model neuron found in the spinal cord; 3. neurons found in the CNS- local interneuron, projection neuron, and neuroendocrine cell |
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Term
| communication in the nervious system |
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Definition
| voltage potential exists across the membrane due to ability to distribute ions non-uniformly across the cell membrane with extracellular portion positive and negative intracellular portion; can transiently alter the voltage potential across the membrane and propagate this potential change from one point to another within the neuron; a graded voltage change spreads passively and declines with distance in receptive area of the neurons and integration results from summation of all these inputs and at the trigger zone if there is enough depolarization an AP results that propagates down the axon to the synapse causing influx of Ca and release of neurotransmitters |
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Term
| types of neurotransmitters |
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Definition
| classical-ACh, amino acid (glutamate, aspartate;GABA, glycine), biogenic amines (dopamine, serotonin, histamine, norepinephrine); non-classical- peptide transmitters, opioid transmitters, NO (recently discovered) |
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Term
| neural basis for simple behvior |
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Definition
| occurs in reflex; vibration lengthening receptor generates an AP in sensory neuron, this goes to spinal cord and synapses on motor neuron which innervates the muscle to cause contraction |
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Term
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Definition
| AP contains relatively little specific info it is either there or not and does not have precise info transfer it is rather the specific neuronal circuits that give signals meaning (visual pathway interpreted as light) |
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Term
| neurological exam assessment |
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Definition
| mental status, cranial nerves, motor systems, reflexes, coordination and gait, sensory systems |
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Term
| nervous system organization |
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Definition
| 1. spinal cord-processes sensory information from trunk and extremities, autonomic functions, and motor innervation of muscles, of trunk and extremities; brainstem (medulla, pons, midbrain); diencephalon (thalamus, hypothalamus); cerebral hemispheres, and cerebellum |
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Term
| functions of the brainstem |
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Definition
| 1. medulla-cranial nerves 9-12, regulation of blood pressure and respiration, an posture and balance; pons-cranial nerves 5-8, regulation of blood pressure and respiration, eye movements, posture and balance, sleep/wake cycle and general arousal; midbrain-cranial nerves 3,4, eye movements, sleep/wake cycle and general arousal |
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Term
| functions diencephalon and cerebrum |
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Definition
| thalamus-gateway to cerebral cortex for sensory and motor functions; hypothalamus-controls autonomic and endocrine functions and sleep/wake cycle; cerebral hemispheres-cognitive functions underlying comprehension of external world, language, learning, memory, emotions, and behavior; cerebellum-coordination and balance associated with all movement activities |
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Term
| parts of cerebral hemispheres |
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Definition
| 1. comprehension in back end of the brain and comprehension of external world; generating behavior-in the front of the cerebrum and functions in what you are going to do and execution of it |
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Term
| functional systems of brain |
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Definition
| sensory-information about external world and body (somatosensory, visual, auditory, taste, and olfaction); motor systems-effectors of behavior (descending motor pathways-generation of power, regulatory systems-generate power appropriately, eye movements); autonomic nervous system-homeostasis; cerebral cortex-cognitive functions, learning and memory, emotions, language, behavior, and attention |
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Term
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Definition
| includes sleep/wake cycle, and selective attention during wakefulness; found between comprehension and behavioral choice areas of the brain |
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Term
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Definition
| cognitive processes by which we understand the world around us and our relationship to the world-makes sense of the stimuli |
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Term
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Definition
| cognitive processes that underlie judgements, planning, and decision making |
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Term
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Definition
| divides the cerebral hemispheres in half and contains the superior sagittal sinus |
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Term
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Definition
| 1. frontal-front of the brain seperated from the parietal lobe by the central sulcus and temporal lobe by lateral sulcus; pareital lobe-seperated by lateral sulcus to temporal lobe; 3. occipital lobe-formed by imgainary line that goes from preoccipital notch to the longitudinal fissure to demarcate from parietal lobe |
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Term
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Definition
| seperates temporal and parietal lobes and has precentral gyri (primary motor cortex) and postcentral gyri (primary somesthetic cortex) |
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Term
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Definition
| 1. medulla-consisting of the closed and open portion (part that abuts the 4th ventricle); 2. pons-consists of base and tegmentum that is closer to the 4th ventricle; 3. midbrain-has tectum with superior and inferior colliculi and the cerebral aqueduct going through to third ventricle |
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Term
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Definition
| consists of 1. thalamus-lateral to the third ventricle; 2. hypothalamus |
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Term
| sulci and gyri of cerbral cortex |
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Definition
| 1. calcurine sulcus sepearating the cuneus gyrus and the lingus gyrus of the occipital lobe; 2. parieto-occipital sulcus seperating occipital and parietal lobe; 3. corpus callosum-connects two hemispheres together and above is cingulate gyrus and anterior commisure connects the temporal lobes and a line from here to optic chiasm demarcates the anterior hypothalamus; 4. fornix runs over the interventricular foramen going from third to lateral ventricles |
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Term
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Definition
| cranial nerves 9-12 with XII located in preolivary sulcus and IX-XI located in postolicary sulcus and pyramids and olives |
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Term
| parts of rest of brainstem |
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Definition
| pons-middle cerebellar peduncle, VII and VII cranial nerves, VI more medial, and cerebellopontine angle, and trigeminal nerve; midbrain-location of interpeduncular fossa, occulomotor nerve; diencephelon-mamillary bodies, infundibular stalk, optic nerves, optic chiasm and optic tracts |
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Term
| protein synthesis in neuron |
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Definition
| largely restricted to neuron cell body and to lesser extent the dendrites and axons have very limited capacity and axon is dependent on cell body for proteins to maintains its structure and function |
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Term
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Definition
| process by which proteins are delivered to the axon, which is an energy dependent process to go anterograde and retrograde transport (to and from axon terminal) |
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Term
| major classes of axonal transport |
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Definition
| 1. anterograde fast transport-delivers membrane components and other materials to the axon and axon terminal for electrical properties and synaptic transmission (includes mitochondria); 2. fast retrograde transport-degradative pathway that returns material to the cell bodies (also way in which trophic factors released by target cells are delivered to cell body to promote neuron survival and viruses as well); 3. slow axonal transport-delivers cytoskeletal components, metabolic enzymes and other proteins |
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Term
| discovery of axonal transport |
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Definition
| radioactive AAs added to extracellular space and taken up by cells and incorporated into proteins and look at distribution along the axon and see a spike along the axon |
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Term
| motor proteins of axonal transport |
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Definition
| is microtubule dependent and consists of 1. kinesin-towards + ends and anterograde direction towards terminal with MT binding domain with cargo domain and ATPase to power movements; 2. dynein-towards - ends in retrograde direction with MT and cargo binding domains and dynactin as accessory binding protein |
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Term
| types of neurotransmitters transported by axonal transport |
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Definition
| 1. peptide NTs- where peptides are formed in the cell body and packaged into vesicles and moved down to axon terminal; 2. non peptide NTs formed in axon terminal and axonal transport brings membrane precursors to synthesize and package these NTs |
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Term
| Poly Q expansion diseases |
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Definition
| 1. Huntingtons disease-increase in caudate and putamen in basal ganglia and impair fast transport, in squid giant axons added pathogenic hungtintin impaired function and forms abnormal aggregates; 2. Alzheimers-amyloid plaques form by product of APP and may cause neurofbrillary tangles of hyperphosphorylated tau |
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Term
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Definition
| when injury or disease causes axtomy function can be restored by this process whereby severed axons re-grow and re-establish contact with cells denervated by the injury occurs in PNS but not in CNS |
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Term
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Definition
| 1. diffusion-cell body to axon tip is not very efficient; 2. transport-much more effiencient |
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Term
| process of axonal regeneration |
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Definition
| 1. distal axon-entire portion of axon distal to injury degenerates (Wallerian degeneration, also degenerate short distance proximal to the injury); 2. Schwann cells-at injury site and along distal stump proliferate and assist in regeneration and myelin associated with distal axons is removed by phagocytic activity and invading macrophages; 3. cell body-axotomoy results in increased expression of proteins involved in axonal growth |
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Term
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Definition
| injured neurons may exhibit decreasing in Nissil staining, nucleus is displaced to eccentric position and the cell body swells |
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Term
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Definition
| when axon is severed, target cells shrink in size=denervation atrophy, mass of muscle can decrease by as much as 80%; this can be detected within 1-2 weeks after axotomy from disuse and loss of trophic support that maintain normal metabolic state of the muscle and there is a net proteolysis of muscle proteins |
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Term
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Definition
| muscle mass will decrease in size but relative to denervation it progresses musch more slowly; denervation atrophy also occurs in the CNS but can only be evaluated post-mortem |
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Term
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Definition
| portion of axon remaining attached to the cell body is the proximal axon; regeneration begins by elongation of axonal sprouts will grow through the lesion site and into portion of the nerve distal to the lesion site into the distal stump composed of cellular and non-cellular components of the nerve such as Achwann cells, CT, BVs, etc. |
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Term
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Definition
| 1. focal crush injuries-endoneurium and basal lamina of Schwann cells remain intact and forms physical pathway that guides regenerating axons and greatly facilitates axon growth to distal nerve stump; 2. transected-whe nerve is damaged along a long portion of its length the continuity of basal lamina, endoneurium and perineurium and epineurium across the injury site is lost and impairs regeneration, proliferatin Schwann cells aid regeneration by migrating into the injury site and forming a pathway that bridges the gap between the cut ends of a severed peripheral nerve sometimes surgical intervention is used; rate of regeneration is 1mm/day or 1 inch/month and regeneration is better proximally and in younger individuals and maturation process must occur as well |
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Term
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Definition
| distal axon degenerates, myelin associated with distal axons is phagocytized but relatively slowly, astrocytes, vascular and microglial elements respond to injury by proliferation and migration into the injured area which leads to formation of a glial scar, proximal axons initiate a regenerative response which is rapidly aborted |
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Term
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Definition
| 1. neurons have potential to grow but injury in CNS does not lead to upregulation of growth associated proteins in injured neurons and limits intrinsic potential of CNS neurons from regenerative growth; 2. molecules in injured CNS suppresses axonal growth include myelin debris, chondroitin sulfate proteoglycans secreted by astrocytes and glial scar forms a mechanical barrier |
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Term
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Definition
| proteins that have been indentified that promote the survival and differentiation of neurons; function throughout lifespan to maintain neuronal viability |
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Term
| sources of trophic factors |
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Definition
| 1.neurons synthesize trophic factors transport them to the axon terminal where they are secreted to regulate metabolic state of traget cell (denervation atrophy); 2. target synthesize and secrete trophic factors that regulate metabolic state of the neurons that innervate them (responses to axotomy triggered by interuption of supply of trophic factors; 3. supporting cells synthesize and secrete trophic factors that regulate the metabolic state of the supporting cells with whihc they are associated |
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Term
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Definition
| ectoderm overlying the notochord that thickens entering the third week and it begins to fold and lateral edges begin to come to the midline consisting of two neural folds that meet and form the neural tube |
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Term
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Definition
| is first formed in cervical region and proceeds in both cephalic and caudal direction |
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Term
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Definition
| group of cells at the junction of the neural plate and the remaining ectoderm also differentiate and become located lateral and dorsal to neural tube |
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Term
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Definition
| neuroectodermal cells that make up the wall of the neural tube and these cells surround a central canal and these cells give rise to neuroblasts that form a peripheral layer around the neuroepithelial cells called the mantle layer |
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Term
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Definition
| neuronal processes from the neuroblast cells extend peripherally from the mantle lyaer and a collection of these fibers and these become myelinated to form white matter of the CNS |
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Term
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Definition
| differentiated neuroepithelial cells and these will develop into supportive cells or neuroglia found in the CNS include ependymal cells, astrocytes, and oligodendroglia |
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Term
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Definition
| in diamond shaped central canal the corners are a sulcus and represents the dividing line between the dorsally locate alar plate (sensory) and ventrally located basal plate (motor); region between these regions is intermediolateral portion that will give rise to autonomic neurons |
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Term
| development of neural crest cells |
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Definition
| will divide with segments of the somites and will develop into sensory neurons, autonomic neurons found in ganglia and supportive cells of PNS (Schwann cells) |
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Term
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Definition
| contain two types of motor neurons; 1. somatic efferent neuron located in anterior horn of the gray matter and transverse the ventral root to reach the spinal nerve; 2. visceral efferent neuron-located in the intermediolateral portion of the gray matter and exit the spinal cord as preganglionic fibers and exit through the ventral root and travel to communicating ramus to the sympathetic chain and either synapse here or else in other ganglia in abdomen or pelvis and postganglionic fibers innervate visceral structures |
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Term
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Definition
| sensory neurons with cell bodies located in dorsal root ganglia some arise from viscera and are call VAs and second arises from somatic structures and are SA and these fibers synapse in the sensory portion of the gray matter that was derived from the alar plate |
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Term
| organization of neural tube |
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Definition
| SHH is used to determine vental-dorsal patterning secreted by the notochord and causes ventral neuroepithelial cells to secrete it and it forms a gradient and fuzzy gradients are set up and other gene interaction sharpens the borders and determines the different cell types |
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Term
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Definition
| by 4th week have 1. prosencephalon (forebrain); 2. mesencephalon (midbrain) and 3. rhombencephalon (hindbrain) |
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Term
| subdivisions of parts of the brain |
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Definition
| prosencephalon enlarges and lateral extensions appear forming the telencephalon and are connected by the diencephalon; mesencephalon remains as a single structure and rhombencephalon develops into metencephalon and myelencephalon |
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Term
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Definition
| hindbrain has 8 rhombomeres due to variable expression of HOX genes to convey AP axis of caudal brain stem; OTX is expressed in neural plate and once expressed then FGF8 becomes the signaling molecule for Engrailed; in forebrain SHH designates the midline and ventral structures of the CNS the anterior neural ridge secretes FGF8 and FGF8 brain factor 1 that regulates the development of the telecephalon and NKX2.1 regulates the development of the hypothalamus |
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Term
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Definition
| 1. cephalic flexure-appears in the region of the midbrain or mesencephalon; 2. pontine flexure is located at junction between the metencephalon and the mylencephalon and eventually gives rise to the rhombic lip and become the cerebellum; 3. cervical flexure appears at the medulla-spinal cord junction |
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Term
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Definition
| enlarges in the brain except in the midbrain and develops into ventricles that will contain the cerebrospinal fluid |
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Term
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Definition
| develops into the medulla and the caudal end remains closed with a central canal continuous with the central canal of the spinal cord and as the cephalic end of the medulla is reached the roof of the ventricle opens and is drawn out as the roof plate |
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Term
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Definition
| heavily vascularized parts of the tela choroidea that arises from the pia and roof plate |
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Term
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Definition
| develops into the cerebellum and the pons and the cephalic part of the 4th ventricle continues into the pons, the roof plate becomes superior medullary velum that will be covered by the cerebellum and the mantle layer of the rhombic lip will develop into the deep nuclei of the cerebellum and will give rise to cells that will form the cerebellar cortex |
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Term
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Definition
| changes very little and central canal is small and called cerebral aquaduct and the roof plate and alar plate become the tectum (nuclei with vision and hearing) and the floor and basal plates become the cerebral peduncles |
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Term
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Definition
| develops into thalamus, epithalamus, subthalamus and hypothalamus and central canal forms the third ventricle and are continuous with the lateral ventricle via the interventricular foramina; does not have a basal plate and alar plate divides into a dorsal and ventral region; the thalamus is located in the dorsal region and is major set of relay nuclei and ventral region is comprised of hypothalamic nuclei in regulation of visceral function |
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Term
| telencephalon development |
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Definition
| hemispheres flex into a Cshaped structure and mantle layer gives rise to cells of basal ganglia that regulates motor function and gives rise to cells that will migrate into the marginal layer and these cells become the cortical gray cells; internal capsule forms at the line of fusion where medial walls of telencephalon fuse with lateral walls of the diencephalon; central canal of the telencephalon forms the lateral ventricle |
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Term
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Definition
| voltage inside minus voltage outside; voltage taken outside as zero arise from permeability of Na and K if membrane potential is equal to the equilibrium potential of an ion the ion will not flow through the open channel calculated by using the Nerst equation; electrical driving force is voltage difference between Em and Eion |
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Term
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Definition
| the current of an ion is equal to the conductance of that ion multiplied by the difference between Em and Eion; Em will be closer to the more permeable ion; the chord conductance equation uses the conductances of the ions and the Eion of each ion; the transference equation uses the percaentage of conductance of each ion |
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Term
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Definition
| the transference equation also explains the IPSPs and EPSPs; information processing using graded changes in membrane potential to change neurotransmitter release (ie in the retina) |
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Term
| ion conductances and action potential |
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Definition
| Em rapidly depolarizes to becomes positive; AP caused by increase in Na conductance so Em approaches Ena; Na channel inactivates in about 1ms having both an activation gate (m) and inactivation gate (H); the increase in K conductance causes a repolarization of the membrane; maximum rate of ation potential generation is determined by the absolute refractory period (usually at least 2ms) |
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Term
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Definition
| like lidocaine prevent transmission of action potentials to the CNS and binds to sites on the sodium channel and blocks it but has to get inside the cell before it can reach this site; active nerves are blocked more readily; when EC Ph more acidic it is not as effective because the lidocaine is protanated which happens in infected tissue |
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Term
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Definition
| the inward sodium current must equal the outward potassium current and in sodium the conductance is large and in potassium the Em depolarizes |
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Term
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Definition
| propagates without decrement, very little specific information is contained, speed of conduction depends mostly on myelination and diameter; dimensions also affect susceptability to local anesthetics with small unmyelinated fibers being most susceptable (mostly pain fibers); postive charge that enters can go two different ways down the axon or out through the membrane and anything that makes the current travel faster down the axon will make conduction faster and increase the length constant (ie myelin) |
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Term
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Definition
| forces current down the axon longer distance before it can escape and so theres saltatory conduction and electrotonic conduction occurs at the nodes of Ranvier |
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Term
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Definition
| it may not depolarize to the next node to create an AP and have transmission failure since no channels are at other places than nodes of Ranvier; it may also change the threshold or the sensitivity; may allow ectopic impulses; increased mechanosensitivity; and may also allow crosstalk between adjacent demyelinated axons |
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Term
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Definition
propagation of AP to terminal of axon and voltage dependent Ca channels on the terminal opens due to depolarization and Ca enters binds to synaptobrevin/VAMP and causes exocytosis of vesicles and amount of NT released depends on amount of Ca; peptide NTs require a greater amount of Ca and therefore more APs and more time; enzymes to make NT are made in cytoplasm of terminal for small
NTs they are concentrated and packaged into vesicles |
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Term
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Definition
| ACh bind to nicotinic ACh receptor and opens up the ion channel in receptor and Na and K have equal conductance; the reversal potential where there is no net current through the ion channels (about -10mV) |
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Term
| structures of the brain in CT |
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Definition
| 1. CSF in the subarachnoid space is most radioluscent (high water content); 2. bone, contrast enhanced vessels and dural septa are most radiodense; among soft tissues the white matter is more radioluscent than gray matter because the fat reduces is radiodensity; interfaces between white matter and gray matter are normally well defined |
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Term
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Definition
| include falx cerebri, septum pellucidum, third ventricle and pineal gland and are well demonstrated by CT or MRI and a shift of these structures due to a space taking lesion, hemorrhage or edema; the gyri and sulci between them should be visualizable and see radiodense area of CSF around them |
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Term
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Definition
| signal intensities of tissues are determined by proton density, T1 relaxation time and T2 relaxation time; gyri, sulci and white matter-gray matter interfaces are well defined |
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Term
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Definition
| white matter appears as a high signal intensity; gray matter has a moderate signal intensity (gray) and CSF low signal intensity appears black |
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Term
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Definition
| white matter-moderately low signal intensity (dark gray); gray matter-moderately high intensity (light gray); CSF-moderately low signal intensity |
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Term
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Definition
| white matter-low signal intensity; gray matter-moderately high intensity (light gray); CSF-high signal intensity able to see pathology associated with edema but flow voids in vessels |
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Term
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Definition
| local arterial occulsion or by a general reduction in brain perfusion as a hypotensive episode or hypoxia; 1. atherothrombotic-local blood clot superimposed on an atherosclerotic plaque (internal carotid, vertebral; cerebral or brain stem; or small branch of one of these vessels); 2. embolic-aggregated platelets or portion of an atheroma formed in the heart is discharged into the circulation and blocks a distal artery; 3. border zone or watershed infarcts-when systemic reduction in blood flow or generalized hypoxic episode (cardiac arrest or shock, drowning) and border xones between major arterial distributions can suffer an infarct |
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Term
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Definition
| 1. intracerebral hemorrhages-can be caused by hypertension or secondary to an ischemic stroke; 2. extracerebral hemorrhages-can be traumatic as in epidural or subdural hematomas or secondary to rupture of a cerebral aneurysm as in subarachnoid |
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Term
| CT findings in ischemic stroke |
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Definition
| in first few hours there are rarely any CT findings but decreased availability of oxygen and glucose to affected brain area results in decreased production of ATP and Na/K ATPase and causes cytotoxic edema; by 18-24 hours may see early CT signs of the edema-slight hypodense area in affected area, some loss of gray matter-white matter interface by bringing radio density of white and gray matter and subtle mass effect of swelling of the gyri causes thinning or disappearance of the intervening sulci; by 3-5 days the edema reaches a peak and have a well defined hypodense area corresponding to vascular territory of the occluded vessel, brain swelling of large infarcts can cause a large midline shift and can obstruct CSF flow; within weeks or month have degeneration and phagocytocysis of infarct producing volume loss with increased size of sulci and underlying ventricles and a midline shift towards the involved side |
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Term
| other CT findings in ischemic strokes |
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Definition
| 1.border zone infarcts-systemically induced decreased brain perfusion between territories of major arteries when perfusion is most tenuous; 2. lacunar infarcts-commonly involved basal ganglia, thalamus, deep white matter or brain stem caused by hypertension or diabetes-induced arteriolar occlusive disease of deeply penetrating arteries; 3. contrast enhancement around margins of infacrt requires a few days due to vasogenic damage of blood-brain barrier and around periphery of infarct to produce a contrast enhanced ring |
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Term
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Definition
| may occur 1. secondary to ischemic stroke-usually occur one to several days after onset of an ischemic stroke, cause by autolytic processes involving walls of blood vessels within the area of ischemic stroke; 2. spontaneous primary hemorrhages-caused by rupture of intracerebral small vessel aneurysms produced by hypertensive of diabetic vasculopathy; 3. traumatic hemorrhages-intracerebral, epidural, subdural or subarachnoid |
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Term
| hemorrhagic storke CT findings |
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Definition
| because of high hemoglobin iron content CT detects as an immediate hyperdense region conforming to the arterial distribution of hemorrhaging artery (why CT used first to rule out hemorrhage); over 3 days the radiodensity of the clot increases by clot retraction, serum extrusion and hemoglobin concentration with serum forming a hyperdense rim about the hyperdense clot; over 3-5 days edema may increase the hypodense rim; hypodensity of the clot will fade and disappear over 2 months by phagocytosis leaving a hypodense slit at the site of the hemorrhage |
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Term
| MRI of hemorrhagic stroke |
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Definition
| oxyhemoglobin in fresh hemorrhage is nonprarmagnetic so not detected by MRI within few hours turn into deoxyHb which causes it to appear very hypointense on T@ and slightly hypointense on T1 (acute stage) by 3-7 days deoxyhemoglobin oxidized to methemoglobin which is hyperintense on both T1 and T2; over several months methemoglobin is resorbed and the clot is gradually replace by hemosiderin containing macrophages which are hypodense on both T1 and T2 |
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Term
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Definition
| associated with a skull fracture and bleeding is usually from meningeal arteries and the epidural gradually dissects the dura from the bone producing a slow progression of signs and symptoms |
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Term
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Definition
| appears as sharply marginated biconvex radiodensity; compression of the underlying cortex can cause thinning or disappearance of the sulci; inward displacement but preservation of underlying cortical gray-white matter interface; compression of the brain and ventricles with a possible midline shift |
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Term
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Definition
| usually caused by skull-brain acceleration or deceleration shearing stresses the rupture the bridging veins that course from the brain to the fixed dural venous sinus |
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Term
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Definition
| appears as a diffuse cresecent-shaped radiodenisty that may exend onto many surfaces of the brain including cerebral convexity, skull base, interhemispheric fissure, upper or lower surface of tentorium or around brain stem; flattens underlying gyri and thins or causes disappearance of interveing sulci, displaces gray-white matter interface and may compress ventricles or cause brain herniation; acute is hyperdense, and subacute becomes isodense to cortex for 2-6 and chronic beyond 6 weeks becomes hypodense to cortex |
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Term
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Definition
| 1. spontaneous-usually caused by a bleeding aneurysm of one of the major arteries of the brain base or AV; 2.traumatic-involves trauma to arteries at the base of the brain; appears linear or curved radiodensities within sulci or fissure or as larger aggregations in the dilations of the SAS that are called cisterns |
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Term
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Definition
| MRI is much more sensitive; on T2 and proton density appear as high intensity lesions ovoid with the major axis of the plaque parallel to the nerve fiber orientation; often have periventricular disposition in CC and internal capsule but may occur anywhere in the white matter (brain stem and spinal cord); in acute stages there is a break down of the blood brain barrier so MRI with gadolinium during T1 will cause hyperintensity of acute plaques by leakage of the gadolinium |
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Term
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Definition
| begin in internal acoustic meatus as ovoid swellings of VIII nerve that are hypointense or isointense with brainstem on T1 MRI can enlarge and compress cerebellum and brainstem with gadolinium they become hyperintense on T1 MRI |
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Term
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Definition
| CT these tumors are only slightly more radiodense than cerebral cortex but if adjacent to bone commonly show calcification and surrounded by rim of vasogenic edema and with iodinated contrast show increase in radiodensity |
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Term
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Definition
| commonly develop in white matter but may compress or infiltrate adjacent gray matter; in adults tend to appear diffuse and on CT they are hypodense if high grade they show contrast enhancement and surrounding edema because of destruction of blood brain barrier; on MRI low grade astrocytomas are hypointense on T1 images and are very hyperintense on T2 images and do not enhance with gadolinium administration on T1 images however high grade will hsow gadolinium contrast enhancement on T1 images; children astrocytomas usually well circumscribed can be cystic and solid most commonly involve the cerebellar hemispheres and as expand can block the CSF outflow paths from the 4th ventricle and cause distension of all the ventricles or they can compress 4th ventricle directly and cause distension of third and lateral venticles |
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Term
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Definition
| evaluates blood oxygenation as an indicator of brain metabolic activity by an MRI technique called blood-oxygen level determination (BOLD-MRI) |
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Term
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Definition
| measures glucose uptake since fluoroDglucose and concentrates in areas of high metabolic activity |
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Term
| roles functional imaging modalities |
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Definition
| 1. which areas of the brain are involved in specific behavioral in normal individuals; 2. hypermetabolism or hypometabolism of diseases like brain tumors, Alzheimers disease epilepsy; whether patients in a vegetative state retain ability to understand spoken commands and respond to them through brain activity rather than through speech or movement; whether patients with chronic pain can be taught to monitor and control their own brain response to that pain through biofeedback techniques |
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Term
| role of insulin in the brain |
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Definition
| rat studies showed that it was synthesized in the brain and cells within the brain are responsive to the release; those with type 2 diabetes have 2-5 fold increase in Alzheimers and show significant deterioration of cognitive function and emotional stability; one area of the brain affeted is the hypothalamus insulin plays are role in ANS and HPA axis and role to sense glucose levels is important regulating energy homeostasis |
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Term
| role of insulin in Alzheimers |
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Definition
| insulin increases cognitive performance and memory in acute administration but hyperinsulimeia has opposite effect; the insuling receptor activates tyrosin kinase but enzyme that breaks down insulin also breaks down plaques and are in competition with each other (amyloid beta); insulin increases expression of APP and also increases inflammation; not all studies show this correlation |
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Term
| effect of insulin in brain |
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Definition
| enters through peripehral vascularization and receptors throughout the brain; signaling pathway the same but effects different has role in appetite, cognition, and memory also has a cell proliferative role and regeneration role has survival factor by increasing Ca uptake to release neurotransmitters |
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Term
| metabolic syndrome and Alzheimers etiology |
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Definition
| HTN, and infarct can cause decreased blood flow decrease in cerebral blood pressure and cytokines also increase inflammation and this may have a role in the onset of Alzheimers; insulin resistance and IDE; vascular effects, microvascular disease, glucose toxicity, and insulin with amyloid synthesis and release |
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Term
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Definition
| facilitated diffusion through GLUT1 and GLUT3 transporters; GLUT4 is present but limited |
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Term
| monocarboxylate transporters |
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Definition
| 1,2 and 4 expressed in nervous tissue function in transport of lactate, acetate, pyruvate and ketone bodies; ketone bodies are important substrate right after birth will all the fat of milk before mechanisms are mature; MCT2 has lowest Km and predominently neuronal expression and MCT4 very high Km in glial cells in cerebellum and astrocytes in hippocampus |
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Term
| astrocyte-neuron lactate shuttle |
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Definition
| glucose crosses blood-brain barrier and enters cells via GLUT1 and metabolized by glycolysis and TCA cycle leading to complete oxidation; transfer of glucose derived lactate from astrocytes to neurons and used as an energy source; when lactate and glucose are present in equimolar concentration 90% of neuronal oxidative metabolism was supported by lactate |
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Term
| metabolic coupling of firing neuron feeding preferentially on lactate |
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Definition
| Glutamate is taken up by astrocyte with EAAT which is a NA cotransporter and the Na is pumped out and the Glu goes to Gln which both use an ATP and depletes this pool and astrocyte takes up glucose and specific LDH makes pyruvate to lactate and released into EC space and pool of lactate increases and taken up by the neurons and neuron has different LDH to convert lactate to pyruvate |
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Term
|
Definition
| present in lower concentration than liver; and glycogen synthase is present in astrocytes in adults and in neurons in young; concentration is higher than free glucose but low relative to brain glucose consumption; glycogenolysis is locally regulated and does not respond to circulating hormones and peptides; presence of glycogen in neurons is cytotoxic |
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Term
| time frame of glycogen metabolism in brain |
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Definition
| glycogen is depleted during hypoglycemia with a period of supercompensation occuring 6-8 hours through gene expression by phosphatase that increases glycogen synthase activity and brain lacks significant expression of G6Phosphatase; both lactate G6P pass through gap junctions and lactate diffuses out of astrocytes can can be taken up by neurons |
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Term
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Definition
| autosomal recessive neurodegenerative disease with monoclonus and tonic clonic seizures and death usually occurs within 10 years of presentation; due to presence of insoluble poorly branched glycogen in cytoplasm of cells |
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Term
| defective genes in Lafora disease |
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Definition
| laforin is EPM2A and is dual specificity phophatase with carbohydrate binding domain (60% of cases); malin EPM2B is E3 ubiquitin ligase and associates with laforin (30% of cases) ubiquinates variety of targets with laforin and regulating glycogen metabolism; gylcogen will be hyperphosphorylated and causes aggregates of poorly branched insoluble polymers |
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Term
| mechanism of Lafora disease |
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Definition
| protein targeting to glycogen and AGL (glycogen debranching enzyme) both bind nascent glycogen via CBM and glycogen is phosphorylated during an early step and laforin is targeted to the glycogen particle via its CBM and releases the phosphate and interacts with PTG and malin is targeted to laforin and binds laforin via NHL and ubiquinates the proteins and releases them from glycogen particle; malin could down regulate glycogen phosphorylation or regulate formation of gylcogen by regulating the glycogen metabolic enzymes |
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Term
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Definition
| neurological sign is diminished vibration sense with proprioception in the legs; include pernicious anemia, dietary deficiency, and malabsorption; due to defect in methylation reactions and xuccinyl-CoA synthesis; treated with parenteral administration cyanocobalamin IM 2x per week for 2 weeks then weekly for 1 month then monthly; common in elderly and low serum B12 |
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Term
|
Definition
| hematological symptoms recover within two months and mental recovery can occur but depends on their severity and duration most likely in early stage but chronic sufferers have smaller chance of recovery; less than 50% have complete neurological recovery will 90% will have at least 50% improvement |
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Term
|
Definition
| things that are sensed and are continuous with a wide dynamic range of possible values but nerves transmit sensory info as APs which is digital information; all APs have the same amplitude so cannot be used to correlate to stimulus strength; the variable that is transmitted is the frequency of action potential or total number of APs (or timing bursts) |
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Term
|
Definition
| variable that is transmitted by the nerve and max frequency of APs is determined by absolute refractory period but RRP is probably a more realistic determinant; fastest occurs in alpha motorneurons where ARP is only 2-3 ms and can only transmit about 333 to 500 APs per sec and sensory nerves with slower action potentials can generate and transmit fewer APs per second; and in a simple system encoded by only frequency of APs the dynamic range is limited by maximum AP rate |
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Term
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Definition
| required to update the brain to make sure everything still working like 10APs/sec; a large dynamic range is difficult to encode with just one kind of pressure but can activate more receptors and send more signals on parallel paths or can use different types of receptors that measure the same physical entity or can use receptors for different sensory modality (high pressure is perceived as both pressure and pain) |
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Term
|
Definition
| these relationships are common so that at smaller stimuli it is more sensitive at lower ranges; and less sensitive at higher stimuli |
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Term
|
Definition
| design of sensory system so action potential in a nerve is interpreted by the brain as a specific sensation; either specialized epithelial cells-visual system, taste system, auditory system; primary first order afferent neurons-somatosensory system, olfactory system; sensory transduction is the conversion of a stimulus to electrochemical energy in form of a receptor potential |
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Term
|
Definition
| signal is either depolarization or hyperpolarization; a deformation causes a graded potential which might bring the voltage gated Na channels to open and generates an AP; receptors include mechanoreceptors, photoreceptors, chemoreceptors, thermoreceptors, nociceptors (extremes of pressure, temp, or noxious chemicals) |
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Term
|
Definition
| the firing rate subsides when stimulus remains constant |
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Term
|
Definition
| 1. Abeta-myelinated medium diameter medium velocity; 2. Adelta-myelinated, small diameter, medium velocity; 3. C fibers-unmyelinated, small diameter, slow veolcity fibers (these are most sensitive to anesthetics and a fibers are least sensitive) neural transmission can be blocked by pressure with A fibers being most sensitive |
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Term
| cutaneous and subcutaneous somatic sensory system |
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Definition
| informs about light touch, vibration, pressure, cutaneous tension; the receptor itself that adapts not the nerves ability to transmit APs |
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Term
|
Definition
| 1.rapidly adapting-useful in detecting changes or acceleration (tapping or vibration or muscle acceleration); 2. slowly adapting-useful for detecting position, intensity, duration or stimulus or steady forces (steady pressure, skin deformation, muscle position, joint angle) and persistent inward current will keep receptor region depolarized to threshold for APs; touch receptors are either bare nerve endings or encapsulated nerve endings |
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Term
| stretch activated ion channels |
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Definition
| increased membrane tension increases liklihood of channel openings and are found in touch receptors and many other types of cells, it may be tension itself or tension transmitted through cytoskeleton to channels and these channels are usually cation selective (Na, K, Ca) |
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Term
| touch and pressure receptors |
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Definition
| most are encapsulated and use Abeta fibers; free nerve ending are C fibers and A delta fibers some touch receptors but primarily sense pain and temp; slow adapting; Pacinian corpuscle-encapuslated, mostly in subcutaneous layers of non hairy skin, deep pressure ,high frequency, tapping, very rapidly adapting; experimentally removing the encapsulation makes it tonic; Meissners corpuscles-encapsulated by Schwann cells located between dermal papilla in glaborous skin, phasic, small receptive fields (detects 2 point discrimination), low frequency vibration, tapping, flutter; hair follicle receptors-rapidly adapting can sense directionailty of stroking or air currents; Ruffinis corpuscles-hairy skin and joint capsules-encapsulated slow adaptation large receptive fields and detects stretching of skin and joint rotation; Merkels receptors and tactile discs-tonic slowly adapting, touch pressure, vertical indentation of skin and good for detecting edges and shapes |
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Term
|
Definition
| sensors able to sense temp over wide range down to 0 degrees to 60 degree and isolated proteins being to denature above 42 degrees; no one sensor can cover this whole range because AP firing rates would not be adequate; system uses labeled line with multiple thermoreceptors these are members of teh transient receptor potential |
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Term
|
Definition
| ionotropic receptors that allow cations to pass through channel in the receptor; they are excitatory moving Em towards threshold (TRPV1 best known with ligands of heat greater than 43 degrees, H+ outside the cell, and capsaicin); usually have a threshold and then a saturation of response; menthol creates sensation of coolness in TRPM8); the receptors are found in teh endings of specific neurons either a-delta or C fibers the labeled line is important; TRPV4 is warm as is TRP3 |
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Term
| white matter territories in spinal cord |
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Definition
| 1. dorsal funiculus including the funiculus gracilus and cuneatus (only at T6-C1); 2. lateral funiculus; 3. anterior funiculus |
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Term
| gray matter territories in the spinal cord |
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Definition
| 1. dorsal/posterior horn; 2. ventral/anterior horn with medial motor nuclei from axial skeletal muscle and lateral motor nuclei from extremity skeletal muscle (present at C5-T1 and L2-S2) |
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Term
| differences in spinal cord region |
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Definition
| enlargements for cervical and lumbrosacral plexus; lumbrosacral portion more rounded and funiculus gracilus is only in lumbrosacral portion; gray matter in thoracic region is very svelt; have little lateral horn for preganglionic autonomic neurons |
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Term
| blood supply of the spinal cord |
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Definition
| the posterior spinal arteries supply the posterior funiculus; the anterior spinal artery supplies the anterior horn and some of the anterior and lateral funiculus and the arterial vasocorona supplies the anteriolateral funiculus |
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Term
| dorsal white column-medial lemnicus system |
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Definition
| axons are located in posterior funiculus and are central processes of dorsal root ganglion neurons and ascend to the medulla and sense joint position and touch and vibration |
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Term
|
Definition
| extends from lateral and anterior funiculus portion of the spinal cord these axons cross the midline at point of entry and synapse on second neuron in dorsal horn and carry temperature and pain receptors |
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Term
| entry of somatosensory neurons in lumbrosacral |
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Definition
| DWC-ML-neuron 1 enters at dorsal root entry zone, at the fasciculus gracilis with the cell bodies located in dorsal root ganglion; ALS-neuron 1 enters at dorsal root entry zone and synapses on neuron in posterior horn and then crosses midline at anterior white commisure to enter anterior-lateral funiculus |
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Term
|
Definition
| start to see the nuclei gracilis and cuneatus in lower medulla and also still have ALS in the anterolateral portion of the medulla; the nucleus gracilis appears first; the fibers of neuron two of nuclei cuneatus and gracilis form internal arcuate fibers which cross midline under the central canal and end up right above the pyramids of the medulla to form medial lemniscus and the ALS is above the olive; the MLS is supplied by the anterior spinal artery, the ALS by the vertebral artery and remainder by PICA and posterior spinal arteries |
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Term
| somatosensory system in low pons |
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Definition
| the MLS starts to turn and becomes horizontal and the ALS ends up on at the foot of the MLS and these are supplied by the pontine arteries and midpons becomes completely horizontal with ALS at the feet |
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Term
| somatosensory system in midbrain |
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Definition
| the MLS and ALS shift to lateral portion of the tegmentum and the MLS is now upside down with the feet dorsal, medial and dorsal to the substania nigra and crus cerebri supplied by the posterior cerebral artery |
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Term
| somatosensory system in the thalamus |
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Definition
| the cell bodies of neuron 3 is located in the ventral posterior lateral nucleus of the thalamus (VPL) and the fibers project into the posterior limb of the internal capsule which includes motors fibers as well |
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Term
|
Definition
| brings information from the body and from the environment to the cortex includes proprioceptive information (within body); also tactile info which includes pressure, two-point discrimination, and touch; also information about pain, temperature and itch |
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Term
|
Definition
| first order brings info to the CNS; the second order neuron may or may not cross but travels from the spinal cord or brainstem to the thalamus; third order neuron travels from thalamus to the cortex |
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Term
| path of touch and proprioception |
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Definition
| touch from the limbs and trunk conveyed to the cortex via ML/PWC pathway from the head and neck is conveyed via the 5th CN and the trigeminothalamic tract; for proprioception follows the PWC/ML for trunk and extremities and head proprioception follow V nerve to the mesencephalic nucleus |
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Term
| conscious proprioception information conveyed |
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Definition
| to cortex via the PWC/ML pathway or the CN/trigeminothalamic pathway; and unconscious proprioception is brought to the cerebellum via the spinocerebellar pathway and travels over the spincerebellar tracts |
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Term
| pathway of tactile/mechanorecptor and proprioception |
|
Definition
| get to spinal cord from the dorsal root ganglion and myelinated fibers enter the more medial dorsal root entry zone (central processes of DRG) and send branches directly into dorsal funiculus and ascend without crossing to the medulla where they synapse on the nucleus the lower extremity fibers located more medially and upper extremity fibers are more laterally; synapse on second order neurons in necleus gracilis or nucleus cuneatus cross the midline as internal arcuate fibers and ascend via medial lemniscus to the thalamus |
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Term
|
Definition
| gets to brainstem via cranial nerve 5, first order located in trigeminal ganglion the neurons for tactile sensation and mechanoreceptors synapse in the main sensory nucleus of CN5 located in mid to upper pons level most axons cross the midline to ascend in the ventral trigeminal thalamic tract to the thalamus; info from muscle spindles and Golgi tendon organs travel via CN5 have nerve cell bodies in mesencephalic nucleus of CN5 and these neurons will then synapse in the main sensory nucleus of CN5 and then ascend the ventral trigeminal thalamic tract and these axons synapse in the synapse on VPM neurons that go to postcentral gyrus via posterior limb of internal capsule |
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Term
| thalamic neurons containing somatosensory information |
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Definition
| synapse in the primary somatic sensory cortex located in the postcentral gyrus (Brodmanns areas 3,1,2) and the thalamic nuclei synapse on neurons in layer 4 in the somatosensory cortex there are 6 layers and layer 4 neurons transmit info to other cortical layers and neurons in layer III project to other cortical regions; neurons in layer 5 project to subcortical regions including basal ganglia, brainstem, and spinal cord and neurons in layer VI project back to the thalamus |
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Term
|
Definition
| primary somatosensory cortex as hanging at knees and intraabdominal is in lateral sulcus |
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Term
| projection from primary sensory cortex |
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Definition
| are projected to unimodal somatosensory association cortex and these respond predominantly to inputs from a single sensory modality and for somatosensory information in areas 5 and 7 of the parietal lobe; here it is able to differentiate if it is the same or not |
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Term
| heteromodal association cortex |
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Definition
| defined as those regions where multiple sensory systems have input and here where multiple sensory modalities come together and associations can be made between multiple sensory characteristics of the stimulus (Braille-actual translation of bumps into words and then language) |
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Term
|
Definition
| one of number pathways conveying pain and temperature sensation to higher levels and these pathways are also important in conveying info about the environment and important in arousal |
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Term
| pain and temperature receptors |
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Definition
| are free nerve endings in the skin, nerve cell bodies in the DRG and these are small in diameter and are lightly or unmyelinated and conduct slowly and central processes enter the dorsal root entry one more lateral than the PWC/ML neurons and these 1st order neurons synapse in the dorsal horn and these neurons will cross the anterior white commissure of the spinal cord and these neurons will ascend the spinal cord in the anterior part of the lateral funiculus |
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Term
| pain in temperature in other ascending fibers |
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Definition
| 1. spinoreticular tract ascends to the reticular nuclei found in the brainstem and the reticular neurons project to the intralaminar nuclei of the thalamus and is important in arousal; 2. spinomesencephalic tract-brings info into the midbrain tectum and the information is used both to coordinate eye and head movements and for pain regulation this is important as one turns to see what is causing the pain; 3. periaquaductal gray matter is involved in pain modulation or regulation |
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Term
|
Definition
| in the lateral reticular formation of the medulla, pons, midbrain and in mid pons it comes to lie close to the lateral aspect of the medial lemniscus and they will synapse on neurons of the VPL nucleus of the thalamus just as MWC/ML neurons |
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Term
|
Definition
| nerve cell bodies located in the trigeminal ganglion and central processes descend the brainstem almost to cervical levels and synapse on the spinal nucleus of 5 and the second order neurons cross the midline in region of the synapse and ascend on the opposite side of the body in the ventral trigeminal thalamic tract and these fibers will send off collaterals to the reticular nuclei of the pons and medulla and also send info to the periaquaductal gray matter of the midbrain and the VTT axons will synapse in the VPM nucleus of the thalamus |
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Term
| pain and temp in the thalamus and cortex |
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Definition
| VPL receives from ALS and these project to the primary somatic sensory cortex; the VPM receives from the VTT and the third order neurons will project to the primary somatic sensory cortex |
|
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Term
| other projections of pain and temp from VTT and ALS |
|
Definition
| also project to the posterior thalamic nuclei and medial dorsal nucleus of the thalamus and older pain and temperature pathways also project to these nuclei; third order neurons from posterior thalamic nuclei project to the insular cortex and neurons from medial dorsal nucleus to the anterior cingulate cortex and both porjections play a role in the affective and motivation aspects of pain and memory of painful stimuli |
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Term
|
Definition
| can be modulated by cortical and other brainstem centers and downflow from layers 5 and 6 projecting into brainstem and spinal cord neurons |
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Term
| modulation by neurons in periaquaductal gray matter |
|
Definition
| in midbrain, locus ceruleus in pons and the nucleus raphe magnus in the medulla; neurons in periacquaductal gray project to the nucleus raphe magnus and these are serotonergic and project to the spinal cord and they release serotonin in spinal cord and serotonin excites interneurons which contain enkephalin and release of enkephalin inhibits 1st and 2nd order pain neurons by inhibiting the release of Glu and substance P which are normally released by pain nuclei and are excititory NTs; neurons in the locus ceruleus nucleus of the pons porject to spinal cord and release norepinephrine and these excites interneurons containing enkephalin |
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Term
| somatosensory pathways of the face |
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Definition
| enters the mid pons; spinal nuclei extends from mid pons down to lower medulla almost cervial spinal cord and the tract is just lateral to the nuclei and synapses on second order neuron in the spinal nuclei and the axons cross the midline and synapse in the VPM nucleus of the thalamus ascends in VTT tract; the main sensory nucleus is where primary neurons synapse and the axons either cross midline and go with the VTT tract or rise ipslaterally and synapses in VPM and enters the posterior limb of the internal capsule |
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Term
|
Definition
| the fibers of 7,9 and 10 enter and they synapse on second order neurons in the rostral part of the solitary nucleus of the rostral medulla and these ascend ipslaterally and synapse in the VPM nucleus in thalamus and then goes to the insula cortex for processing |
|
|
Term
| location of the spinal nucleus |
|
Definition
| located in dorsal medulla just lateral to the nucleus cuneatus |
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Term
|
Definition
|
|
Term
|
Definition
| dense, irregularly arranged connective tissue capsule where extraocular muscles insert and has anterior continuation called the cornea (transparent), continuous with the dra near where the optic nerve exits the eyeball and it maintains the shape and size of the eye with slight deviation causing near sightedness of farsightedness |
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Term
|
Definition
| continuous with the sclera at a region termed the limbus, it is transparent, avascular and covered by an epithelium and is where the majority of the light refraction occurs |
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Term
|
Definition
| the anterior portion epithelium is stratified squamous sitting on prominent basement membrane and the posterior epithelium is low cuboidal has nerves; and bulk of cornea is stroma made up of fibroblasts and extracellular matrix and collagen fibers; these cells are called keratocytes that are arranged very orderly (no blood vessels-receive nutrients from fluid); the anterior epithelium is non-keratinized epithelium and has rich nerve supply that contain pain under is Bowman's membrane and under posterior epithelium (endothelium) sits a Descemet's membrane |
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Term
|
Definition
| empty trabecular spaces of internal aspects of the cornea and provides a conduit for the aqueous humor to travel from anterior chamber of the eye to the episcleral veins |
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Term
|
Definition
| middle layer and highly vascular and highly pigmented contains choroid, ciliary body, and iris |
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Term
|
Definition
| formed by primary lens fibers oriented in the anterior-posterior direction; very thin and flat and lose their organelles and nuclei and become filled with protein |
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Term
|
Definition
| overlying the subcapsular epithelium which is layer of cuboidal cells found on anterior surface of the lens and these cells are responsible for the continued production of lens fibers and migrate to equitorial regions where they flatten and undergo mitosis |
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Term
|
Definition
| insert on lens capsule that tethers and function in stretching or relaxing shape of the lens |
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Term
|
Definition
| lens is flat due to tension on zonular fibers and contracting the cillary muscle fibers causes less tension on the fibers and the lens resumes natural rounded position; in relaxed state the ciliary muscle is circular when contracting less tension is on zonular fibers |
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Term
| age related changes of the lens |
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Definition
| loss in elasticity, and loss in transparency causing a catarct |
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|
Term
|
Definition
| retina supplied by central artery of retina from opthalmic division of the internal carotid; supply internal 2/3 of retina and laterally the fovea centralis is devoid of blood vessels |
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Term
|
Definition
| does not have three layers of nuclei allowing more light to come in and interact with photosensitive cones, areas of retina tilted toward fovea and choroid layer vascularizes lower region of the retina |
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Term
|
Definition
| 1. innermost layer-axons of nuceli of optic nerve; 2. nuceli of ganglion cells bipolar shape and one of processes is axon of optic nerve; 3. internal plexiform layer and inner nuclear layer- bipolar neurons that synapse of ganglion neurons of optic nerve; 4. outer plexiform layer and outer nuceli which are the rods and cones; 5. rod and cone layer where nuclei are present and embedded in epithelium of pigment cell layer |
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|
Term
|
Definition
| play role in modifying info and supporting neurons including Muller cells, amacrine cells, and horizontal cells |
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|
Term
|
Definition
| has disks of rhodopsin and light bleaches rhodopsin and causes an influx of Ca changing the Na permeability signal that is transmitted to other layer |
|
|
Term
|
Definition
| have iodopsin; the pigmental epithelial cells lysosomes digest shed disks and have melanin between rods and cones discs to prevent extraneous light from activating other cells |
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Term
| blood supply of pigmental epithelial cells and rods and cones |
|
Definition
| choriocapillaris providing nutrients through Bruchs membrane (basement membrane of the pigment cells) and these vessels are susceptible to microanaeurysms in diabetes causing dilations and edema |
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|
Term
|
Definition
| posterior portion of the eye and examination of this region is called fundoscopic examination |
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|
Term
|
Definition
| gel like structure located between the retina and lens and mostly water with some collagen and GAGs (HAs) and as people age collagen fibers bunch together and perceived as floaters and get detachment of vitreous from internal retina and individual sees flashes of light |
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|
Term
|
Definition
| posterior and most extensive portion of the uvea and the innermost portion contains numerous capillaries in a region called choriocapillary layer nourishing the outermost layers of the retina |
|
|
Term
|
Definition
| contains smooth muscle cellls involved in changing the shape of the lens when we focus on objects; irregular foldings extending from ciliary body are ciliary processes that attach to the lens capsule via suspensory ligaments |
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|
Term
|
Definition
| made by epithelium and cells actively transport ions and water forming aqueous humor formed on cells of ciliary process and goes into anterior chamber and reabsorbed in trabecular meshwork into canal of Schemn and into episcleral veins |
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|
Term
| pathologies of anterior chamber |
|
Definition
| if there is a blockage pressure builds up as in glaucoma and backs up on retinal vessels and compromises the bloody supply to the retina and causing difficulties in vision |
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|
Term
|
Definition
| anterior portion of uvea, opaque adjustable diaphragm controlling amount of light entering pupil and stroma of iris contains pigminted cells the posterior portion is covered by a bilayered pigmented epithelium continuation of non-neuronal retina |
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|
Term
| regulation of light entering pupil |
|
Definition
| 1. constrictor muscles around the edges of the iris causes the pupil to get smaller by PS autonomics in CNIII; 2. dilator-smooth muscle on posterior aspect of the iris, longitudinal, autonomic regulation by sympathetics contracted and pulled towards sides to allow more light to enter |
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Term
|
Definition
| framework of supportive tissues composed of dense CT and smooth and skeletal muscles; outer epithelium is same found in skin |
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Term
|
Definition
| sebaceous glands that occur in the eyelid that secretes in product onto the tear film covering the cornea |
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|
Term
|
Definition
| covered by a thin stratified columnar epithelium with goblet cells (palbepral conjunctiva with bulbar conjunctiva found at the later margins of the cornea) |
|
|
Term
|
Definition
| serous glands that secrete a substance that contain lysozyme that serves as an antibacterial agent and have myoepithelial cells between secretory cells and the basal lamina |
|
|
Term
|
Definition
| in left visual hemifield-the furthest left goes onto the left nasal retina, and binocular onto the left nasal retina and right temporal retina; right visual retina-monocular right nasal retina, binocular right nasal retina and left temporal retina; in optic chiasm the ganglion cell axons the nsal retina axons cross and the temporal axons dont cross |
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Term
|
Definition
| goes from optic nerve to optic chiasm to optic tract and synapses on the lateral geniculate nucleus and these project into the primary visual cortex (area 17) by optic radiations |
|
|
Term
|
Definition
| in the occipital lobe and consist of the cuneas gyrus and the lingus gyrus seperated by the calacine fissure |
|
|
Term
|
Definition
| 1. retrolenticular fibers- fibers crossing through the parietal lobe and fibers representing superior retinal quadrants; 2. sublenticular fibers-have a Meyers loop as they move through the temporal lobe and are fibers representing inferior retinal quadrants |
|
|
Term
| superior/inferior visual fields |
|
Definition
| the inferior visual fields go through retrolenticular fibers and end up in the cuneas gyrus; superior visual fields go through sublenticular fibers to get to lingula gyrus |
|
|
Term
|
Definition
| 1. where (magnocellular) stream-move towards parietal lobe in lateral surface and are used in location in space and movement to posterior parietal cortex (M-type ganglion cells large cells and dendrites and axons-rods, color insensitive in retinal periphery); 2. What (parvocellular) stream-object identification on medial and inferior aspect used in color and form to inferior temporal cortex (P-type retinal ganglion cells, small cell bodies and axons and dendrites, input from cones and color sensitive predominate in fovea) |
|
|
Term
| where and what streams of visual processing |
|
Definition
| 1. where (MC) visually guided movements and lesions result in deficits in visual guided movement; 2. what (PC) stream-object identification, lesions result in agnosia |
|
|
Term
|
Definition
| involves projections from optic chiasm to pretectum have a direct constriction of pupil in response to increased illumination causes a direct reflex response in ipsilateral eye and consensual reflex response in contralateral eye; the pretectal area projects bilaterally |
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|
Term
|
Definition
| optic nerve and retina supplied by opthalmic artery a branch of the internal carotid artery giving rise to central retinal artery and posterior ciliary arteries supplying the retina; optic tract and chiasm derive blood from anterior cerebral, middle cerebral artery and posterior communication artery; the optic radiations is middle cerebral artery and striate cortex is posterior cerebral artery on the medial aspect and have some overlap with the middle cerebral artery |
|
|
Term
|
Definition
| out number neurons 10 to 1 an dhelp maintain neurons by providing them energy for neural firing, support for signal transmission, control of blood flow and as well as immune surveillance to protect neurons from viruses and bacteria; four types: astrocytes, oligiodendrocytes, microglia, ependymal cells and in PNS there are Schwann cells and satellite cells |
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Term
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Definition
| most numerous of glial cells and are important in intelligence, information transport, development, migration, production of NTs, homeostatsis, blood flow, blood brain barrier; provide neurons with glutamate as a neurotransmitter and mediate synaptic remodeling important in learning, memory and plasticity |
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Term
| mechanisms for astrocyte mediated functions |
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Definition
| produce number of factors that mediate blood flow such as eicosanoids and prostaglandins and NF kappa beta producing cytokines that mediate inflammatory processes |
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Term
| effect of astrocytes increasing blood flow |
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Definition
| more active area cause astrocytes to produce PGE2 from neuronal activity that vasodilate the blood vessels to increase blood flow |
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Term
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Definition
| in inflammation the BB barrier can be breached by NFKB released by astrocytes producing toxic cyto kines; reactive astrocytes are activated and cause scarring gliosis and angiocidin overexpressed in these astrocytes |
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Term
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Definition
| specialized macrophages and comprise 5-20% of brain cells and present to T cells, mobile and proliferate, secrete cytokines, capable of phagocytosis, and involved in autoimmune disease; can be beneficial as well as contribute to the pahtogenesis of CNS disease |
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Term
| role of microglia cells in Alzheimers |
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Definition
| can be neuroprotective by degrading plaques and anti inflammatory drugs that inhibit microglia activation can improve the behavioral performance |
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Term
| microglia cells in Huntingtons disease |
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Definition
| progression of disease can be monitored by measuring systemic cytokine release triggered by mutant huntingtin protein in microglia cells |
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Term
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Definition
| mutant free radical scavenging enzymes are present in the microglia and have lost their neuroprotective activity and contribute to the progression of AML (SOD1 gene) |
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Term
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Definition
| ApoE mediated phagocytosis of beta amyloid proteins and inhbits of progression of disease and ApoE2 is more effective at this; also important in AIDS dementia microglia stimulate TNFalpha stimulating astrocyte to produce glutamate that causes overstimulation of neurons and cause neuronal death |
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Term
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Definition
| insulate axons for more efficient electrical signal propagation and it is myelin sheaths, dielectric phospholipid bilayer consisting of 20% protein and 80% lipid and many neurodegenrative dieases involved the destruction of this myelin sheath |
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Term
| role in vitamin B12 for myelin regeneration |
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Definition
| help in synthesis of myelin and function in succinylCoA to myelin; also HDAC proteins used to compact chromatin which has been shown to improve myelin repair |
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Term
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Definition
| produce all movements and postures are found in spinal cord and brain stem and are in ventral gray matter of the spinal cord and are alpha motor neurons and gamma motor neurons |
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Term
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Definition
| provide innervation of extrafusal skeletal msucle fibers that produce the force of contraction of skeletal muscles |
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Term
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Definition
| distribute to small intrafusal muscle fibers within the neuromuscular spindle which make no significant contribution to the forces that skeletal muscles generate and control the sensitivty of neuromuscular spindle |
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Term
| anatomically arranged lower motor neurons |
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Definition
| ventral gray matter of spinal cord medially situated alphaMN clusters innervate the medially situated axial or trunk muscles and more laterally located cluster innervate more distally located structures and more dorsally located neurons cause flexion and the more ventrally located neurons produce extension |
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Term
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Definition
| functional unit of a skeletal muscle which is an alphaMN and all of the skeletal muscle fibers it innervates; vary in size in accord with functional demands and muscles requiring fine motor control have motor units with only several muscle fibers; grosser movements and generation of larger forces can have motor units containing a thousand of more skeletal muscle fibers; the force which a voluntary muscle generates is determine by the number of motor units activated and the rate of discharge of the motor units and function of all the excitatory and inhibitory synaptic inputs of the alphaMNs |
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Term
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Definition
| 1. somatic afferents-end directly on and alpha motor neuron to produce stretch reflexes; 2. interneurons-relatively short neurons interposed between a sensory and motor neuron (reflex) or descending motor pathways and LMNs where they can modulate the UMN to the LMNs; 3. some terminals of UMN end directly on lower motor neurons |
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Term
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Definition
| 1. collaterals from primary somatic afferents-producing local circuits important in stretch and withdrawl reflexes from NMS, golgi tenden organ and cutaneous tactile and pressure receptors, pain and temp and proprioceptive afferents; 2. receive corticospinal UMN input-from motor areas of the cerebral cortex most important in conveying motor programs for fine motor control of distal muscles of the limbs; 3. UMN input from brainstem nuclei- like the reticulospinal, tectospinal, and vestibulospinal tracts and the brainstem nuclei receive input from the motor areas of the cerebral cortex important for postural control of trunk and proximal limb muscles |
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Term
| inputs of motor areas of cerebral cortex that assemble the motor program |
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Definition
| 1. primary somatosensory cortex from unimodal and multimodal cortices-sensory guidance to motor activity; 2. prefrontal cortex-exercises judgement about the appropriateness and the short and long term consequences of motor action choices; 3. cerebellum-via the thalamus coordinates motor activity and via sensory feedback compares teh motor action carried out with the intended motor program; 4. basal ganglia-enhance the selection of intended motor activites and suppress unintended motor activities |
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Term
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Definition
| involuntary patterns of muscle contraction and relaxation elicited by afferent stimuli occur at spinal cord and brain stem maybe simple two neuron monsynaptic reflexes; have six common features-receptor, afferent neuron, central connections, efferent neuron, effector, and brain (descending control) |
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Term
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Definition
| in normal adult human usual stimulus is pain causing withdrawl of muscles ; collaterals of the same nociceptive afferents project into spinal gray to terminate on INS involved in 1. diverging circuits-spread the unisegmental afferent stimulus to multiple spinal cord segments to excite the KMNs to all teh muscles necessary to withdrawl the entire limb (spatial divergence); 2. reciprocal inhibition-of the LMNs to muscles that are antagonistic to the withdrawl muscles mediated by inhibitory INs; 3. oscillatory circuits-to provide a prolonged repitive motor afterdischarge of the LMNs so that even after the brief stimulus is terminated the part is not brought back into contact with the injuring agent (temporal divergence) |
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Term
| crossed support extensor reflex |
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Definition
| withdrawl response of one lower limb requires the contralateral limb to bear twice the load to be able to do the contralateral limb must increase the force of contraction and this is mediated by INs and cross the midline and excite alpha motor neurons and may serve as a building block for more complex motor routines such as the stance phase of gait |
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Term
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Definition
| composed of a group of small intrafusal muscle fibers enclosed within a fusiform connectiv etissue capsule and innervated by a sensory and motor nerve fibers; connective tissue capsule attaches to the CT stroma of the muscle and some of the IFMFs (nuclear bag) penetrate the capsule and gain direct attachment to adjacent extrafusal fibers |
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Term
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Definition
| 2-12 thin IFMFs within the capsule and divisable into two group; 1. nuclear bag fibers-have nuclei aggregated in a bulging equatorial area; 2. nuclear chain fibers-have nuclei arranged in a single row or chain at the equator of the fiber and commonly attach at either end to nuclear bag fibers; each spindle receives one group Ia afferent fiber which breaks up to form primary sensory ending that spiral around equatorial regions of both nuclear bag and chain fibers and receives one group of II afferent fiber which breaks up to form secondary seonsory ending adjacent to the equatorial region of nuclear chain and some nuclear bag fibers and each spindle receives gammaMNs of two functional varieties which terminate on the ontractile polar regions of both fiber types |
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Term
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Definition
| group of collagen bundles of the tendon which are enclosed by a CT capsule and innervated by one group Ib afferent fiber that breaks up inot a number of branches which spiral around the surfaces of the collagen fibers and located at the musculotendinous juntion in series with a number of EFMFs |
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Term
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Definition
| terminals have high threshold to externally applied stretches, usual simtulus is contraction of the EFMFs fibers in series with their Golgi tendon organs and shortening of these fibers causes maximal tensile stress on the tendon and Ib fibers act through at least one inhibitory IN that causes inhibition of alphaMNs to the muscle in which the stimulus arose and through excitatory INs excitation of MNs to antagonist muscles; used to relieve a muscle cramp by placing the cramped muscle under an additionaly externally applied stretch |
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Term
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Definition
| activated by stretching the muscle and reflex motor response is contraction of the stretched muscle; primary sensory endings have a very low threshold for stretch and the stretch is greatest in the equatorial region and generation of nerve impulses in the Ia fiber and primary ending can be activated by a short sharp stretches as in tapping a tendon with a percussion hammer; collaterals of Ia fibers go directly to MNs that innervate the muscle from which they arose and produce excitatory effects on their traget MNs; short sharp stretches elicit a short burst of high frequency impulses to the target MNs and creates a brief twitch like contraction of the muscle (phasic stretch reflex) |
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Term
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Definition
| long sustained stretches produced by passively moving a joint to stretch a muscle or by squeezing the muscle produces a long low frequency impulses in the Ia fiber and causes a low frequency but prolonged excitation of their target MNs producing a small but sustained contraction; other collaterals of Ia fibers operating through inhibitory INs cause inhibition of MN to the muscles which are antagonists; shortening of the EFMFs and release of stretch on their attached IFMFs the resulting slackening of the IFMFs results in decreased firing frequency in the Ia and II fibers and some instances a total silencing of the Ia fibers |
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Term
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Definition
| secondary sensory endings have a relatively low threshold to stretch and are most responsive to slow sustained stretches; impulses generated in the II fibers usually act centrally monosynaptically in same manner as the Ia fibers to cause similar effect primarily in the tonic stretch reflex |
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Term
| static and dynamic response of Ia and II neurons |
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Definition
| static length response-as each new greater length is achieved the Ia and II fibers fire at a greater frequency thought to provide the CNS with info about the steady state length of the muscle; Ia fibers also respond by vigorous firing while the musclelength is actively increasing called dynamic repsonse and once a new steady state acheived the rate of firing of the Ia fibers decreases to one appropriate for the new static length; dynamic response of Ia fiber is thought to represent the afferent limb of the phasic stretch reflex and static responses of the Ia and II fibers are tought to represent the afferent limb of the tonic stretch reflex |
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Term
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Definition
| resistance of a muscle to passive stretch and this is velocity dependent faster the passive stretch is applied the greater the resistance; passive component is the viscoeleastic resitance of the tissues being stretch |
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Term
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Definition
| when activated they cause shortening of the contractile polar portions on each end of the IFMFs since they are fixed at their ends to other IFMFs or to EFMFs causes stretches of their equatorial regions just as externally applied stretches do causes activity in both Ia and II circuits; allow sufficient activity to shorten the IFMFs in proportion to the shortening in the EFMFs; these are coactivated with alpha MNs during most postural and movement activities |
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Term
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Definition
| dynamic MNs and static MNs explains how a given diease process like Parkinsons disease or other basal ganlia diseases can cause a dissociation of reflexia and muscle tone |
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Term
| descending pathways that project to the spinal cord |
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Definition
| 1.vestibulospinal; 2. medial reticulospinal; 3. lateral reticulospinal; 4. tectospinla; 5. corticospinal; other pathways that project to the brain stem-corticobulbular, corticoreticular |
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Term
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Definition
| descend in the anterior white column and anterior part of the lateral funiculus to terminate mostly upon the medially situated LMNs that control the trunk and most proximal limb muscles important in posture and muscle tone; include vestibulospinal, medial reticulospinal, lateral retciulospinal, tectospinal and anterior corticospinal |
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Term
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Definition
| descend the lateral white column to terminate mostly upon the more laterally located LMNs that contrrol more distal limb muscles producing goal directed movement and fine motor control-lateral corticospinal |
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Term
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Definition
| originate in the vestibular nuclei of low pons-upper medulla region; project mostly uncrossed into the anterior funiculus of the spinal cord to terminate in the ipsilateral gray matter; respond to changes in the position or movement of the head in order to maintain upright posture against gravity; excitatory influence on the MNs to anitgravity muscles either directly or through INs influence deep tendon reflexes and muscle tone (influencing inhibitory interneurons) |
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Term
| medial reticulospinal tract |
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Definition
| arises from neurons in the reticular formation in the pons; mostly uncrossed axons descend medially through the medulla where they are situated dorsal to the medial lemniscus and below the medial lemniscus and pyramidal decussation they enter the anterior funiculus and end on mostly ipsilateral MNs and INs has terminations and functions similar to those of the vestibulospinal tracts |
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Term
| lateral reticulospinal tract |
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Definition
| originates from reticular formation of the upper medulla and descends uncrossed into the anterior part of the lateral funiculus of the spinal cord terminates on ipsilateral MNs and Ins-has inhibitory effects on DTRs and muscle tone by mechanisms similar to those of vestibulospinal and medial reticulospinal tracts and suppresses withdrawl reflex |
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Term
| lesions of regions from the brainstem |
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Definition
| have suppressive effect on reflexes and lesions can release these and cause them to become hyperactive and lesions above these pathways can also release these reflexes |
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Term
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Definition
| originates in superior colliculus decussate almost immediately in the tegmentum of the midbrain to enter the contralateral medial pons tegmentum are just dorsal to medial lemniscus and enter medial part of the anterior funiculus and innervate neck musculature; helps generate reflex head turning movements to the side of simuli originating in these sensory systems also play a role in eye movement |
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Term
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Definition
| formed by the cerebral cortical neurons that project without synapse to the ventral spinal gray metter to terminate on MNs and INs and majority of these fibers corss in the decussation of the pyramids in the low medulla |
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Term
| origin of corticospinal tract |
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Definition
| originate in multiple cortical areas which make unique contribution to the control of LMNs and the ascending sensory systems; 1/3 of fibers arise from primary motor cortex, 1/3 from the premotor and supplementary motor cortices of the frontal lobe and another 1/3 from the primary somatosensory and somatosensory association cortices of the parietal lobe |
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Term
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Definition
| brodmanns area 4 occupying the precentral gyrus and anterior portion of the paracentral lobule and have somatotopically organized like primary somatosensory |
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Term
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Definition
| in the form of an upside down homuncullus with the knees hooked over the superior margin of the hemisphere and the leg, foot, and perineum represented from superior to inferior |
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Term
| mosaic pattern of multiple overlapping sites |
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Definition
| multiple separate sites and that these sites overlap with the multiple site of other related movements appears to be structured to permit complex multijoint synergies; movements of the even complex movement patterns involving agonist, antagonist and synergists are encoded by cortical motor neurons |
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Term
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Definition
| body parts are denervated or amputated nearby cortical areas enlarge into the compromised area and active practice of complex finger movements causes the finger cortical areas to enlarge |
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Term
| functions of primary cortex |
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Definition
| act directly on MNs appear to be most important in controlling the distal muscles of the limbs that are involved in highly skilled fine motor control and have a strong bias for controlling the upper limb esp the hand and more medially descending tracts are most important in controlling trunk and proximal limb musculature |
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Term
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Definition
| lateral part of Brodmanns area 6 immediately in front of area 4, somatotropy similar to the primary motor cortex; inputs from cerebellum, basal ganglia, somatosensory and other unisensory cortices, adn multimodal association cortices of parietal, temporal, and occipital lobe; involved in assembly of motor programs in response to external events and plays a major role in providing postural stabilization of trunk and limbs during movement-projects axons on PMC, corticospinal tract or brain stem areas |
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Term
| supplementary motor cortex |
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Definition
| portion of Brodmanns area 6 on medial aspect of superior frontal gyrus immediately in front of area 4 with somatotopy is perineum to perineum with primary motor cortex with rest represented in posterior to anterior sequence receives cerebellar and basal ganlia input and input from prefrontal cortex; importatn in initiating movements in response to internally generated cues like memory or will |
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Term
| parietal lobe primary somatosensory and somatosensory association cortices |
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Definition
| brodamans area 3,1,2, 5 and 7 fibers that project directly into the corticospinal tract are important in modulating the sensory upflow and terminate on trigeminal nuclei, nucleus gracilis and cuneatus and INs in the spinal cord dorsal gray modulating ALS; inhibitory functions of the stimulus but prevent from being actively area |
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Term
| course of corticospinal tracts |
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Definition
| posterior limb of internal capsule with corticobulbars near genu; intermediate part of the crus cerebri of the midbrain; 3. base of the pons; 4. pyramids of the medulla where 80-90% will decussate at low medulla levels to form the lateral corticospinal tract to innervate more distal limb muscles; fibers that do not decussate remain anteriorly situated and enter anterior funiculus as anterior corticospinal tract and terminate in the upper portion of the cord upon medially situated motor neurons of the same or opposite side-innervate trunk and proximal limb; bilateral termination explains why trunk and proximal limb musculature is less involved in unilateral upper motor neurons |
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Term
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Definition
| head at the genu and the upper limb, trunk, and lower limbs fibers situated from front to back of posterior limb of internal capsule; upper limb fibers decussate highest and lower limb lowest and mediolateral display of upper limb, trunk and lower limb is reestablished in lateral corticospinal tract |
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Term
| lesions of corticospinal tract |
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Definition
| anywhere above decussation will produce a contralateral hemiparesis and lesions of lateral corticospinal tract at upper cervical cord levels will produce an ipsilateral hemiparesis |
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Term
| LMN/UMN lesion and DTRs and muscle tone |
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Definition
| since LMN is the motor limb of both phasic and tonic stretch reflexes muscle will by hypoflexic and hypotonic (Flaccid paresis); causes hyperflexia and hypertonia by removing inhibitory effects of descending tracts (spastic paresis or paralysis) |
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Term
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Definition
| stimulation in normal individual of plantar surface causes flexion of all toes and in UMN lesion the release of the withdrawal reflex causes great toe extension and abduction of other toes |
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Term
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Definition
| atrophy-rapid and substantial in LMN because of trophic influence and UMN occurs because of disuse; fasciculatons-when LMNs are damaged they become hypersensitive to circulating neurotransmitters causing them to fire spontaneoously to activaate the entire motor unit producing a visible twitch; fibrillations-death of the LMNs causes the motor end plates of skeletal muscle fibers to become hypersensitive to circulating NTs and cause sponataneous contractions of individual muscle fibers (EMG detectable) |
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Term
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Definition
| patients with IMN lesions demonstrate a transient flaccid paresis or paralysis persisting for a few days and weeks and then converts to hyperflexia and hypertonia associated with UMN spastic paralysis |
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Term
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Definition
| closely accompanies the corticospinaltract through the brainstem which provide cortical control over cranial nerve motor nuclei that innervate skeletal muscle coarse through the genu of the internal capsule; many cranial nerve nuclei receive both crosses and uncrossed corticobulbar innervation so unilateral UMN lesions usually produce no findings (exceptions include facial nerve to lower facial innervation, mostly crossed UMN innervation of hypoglossal, and uncrossed innervation of the spinal accessory motor neurons to the sternocleidomastoid muscle |
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Term
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Definition
| located at midpons level just medial to the main sensory nucleus of V and root fibers course anterolaterally to emerge as motor root of V about the junction of the pons base and the middle cerebellar peduncle |
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Term
| LMN lesions of trigeminal nucleus or its axons |
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Definition
| palpating the absence of contraction of the ipsilateral masseter and temporalis muscles; 2. observing deviation of the chin to the side of the lesion on jaw opening against resistance by loss of the ipsilateral lateral pterygoid muscle; observing palatal deviation away from side of the lesion by loss of tensor veli palatini muscle; hyperacusis by loss of the tensor tympani muscle |
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Term
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Definition
| finger on the chin of patients slightly open mouth and tapping down against your finger with percussion hammer stimulates Ia fibers in mesencephalic nucleus of V and project bilaterally to both motor nuclei of V to produce a jaw closure response in normal individuals the respnse is minimal but with bilateral UMN lesions the response is hyperreflexic |
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Term
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Definition
| situated in low pons tegmentum midway between the medial lemniscus and the spinal nucleus of V and its motor fibers coarse dorsalmedially and superiorly to form an internal genu around the abducens nucleus before turning ventrolaterally to descend to the medulla-pons junction and emerge into the cerebellopontine angle |
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Term
| LMN lesion of facial nerve |
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Definition
| will cause a complete ipsilateral Bells palsy invovling loss of forehead wrinkling, tight eyelid closure, ability to show teeth, forehead wrinkles and nasolabial fold and lesions beyond point where the nerve divides into its branches will only cause partial facial paralysis |
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Term
| UMN lesions of facial nerve |
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Definition
| cause only weakness in the contralateral lower facial muscles while eyebrow raising, forehead wrinkling are normal; can be a dissociation of voluntary and emotional facial responses emotional control pathways appear to descend from the hypothalamus in a dorsal location within the tegmentum of the midbrain and pons and could be uninvolved |
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Term
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Definition
| trigeminal nerve sensory limb and a facial nerve motor limb; if cornea is stimulated with a wisp of cotton ro by blowing on it pain afferents are sensory limb project into the spinal nucleus of V from which neurons project bilaterally to both facial motor neurons to provide an ipsilateral and contralateral blink; if same eye blinks regardless of which eye is stimulated then there is a facial nerve lesion on the side that doesnt blink |
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Term
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Definition
| cylindrical nucleus extends much of the length of the medulla and situated within the reticular formation about midway between the inferior olivary nuclear complex and spinal nucleus of V provides motor innervation to most of the muscles of the larynx, pharynx and palate via the vagus nerve |
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Term
| LMN lesions in vagus nerve |
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Definition
| can cause difficulty in swallowing and speech will be ipsilateral vocal cord visulaized on laryngeal examination; palate will deviate away from the side of the lesion at rest and on saying ahhh; unopposed levator veli palatini and on gag reflex deviates away from the side of the lesion because of the unopposed pull of the intact pharyngeal constrictors; UMN innervation of the nucleus ambiguus is generally bilateral |
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Term
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Definition
| touching one side of the pharynx stimulates IX afferents that project to the nucleus of the tractus solitarus and neurons project bilaterally to both ambiguus nuclei |
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Term
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Definition
| cylindrical nucleus located near midline of much of the length of the medulla just ventral to the spinal canal and lower 4th ventricle and fibers coarse ventrally just lateral to the medial lemniscus and pyramid to emerge from the preolivary sulcus |
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Term
| LMN lesion of hypoglossal nerve |
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Definition
| protruded tongue points to the side of the lesion driven by the intact unopposed contralateral genioglossus and lesion of the ventral medulla may cause an inferior alternating hemiparesis causing ipsilateral tongue paresis and contralateral paresis of the limbs; UMN innervation to genioglossus has fiber cross in the medulla just before terminating and can cause weakness in the contralateral genioglossus a protruded tongue to deviate away from the side of the UMN lesion; LMN will cause rapid atrophy and fasciculations and fibrillations and UMN usually involves the corticobulbars and corticospinals before they cross |
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Term
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Definition
| innervates the ipsilateral SCM and trapezius is located n the ventral gray of the upper cervical cord segments and root fibers emerge from the lateral aspect of the upper cervical spinal cord and ascen through the foramen magnum and posterior cranial fossa before exiting the jugular foramen |
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Term
| LMN accessory nucleus lesion |
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Definition
| causes ipsilateral SCM weakness on turning the chin to the opposite side and ipsilateral trapezius weakness and a UMN innervation of trapezius is crossed while the SCM is uncrossed (so contralateral trapezius and ipsilateral SCM |
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Term
| arterial blood supply of the brain |
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Definition
| originates from the vertebral and internal carotid arteries; and numerous arterial-arterial anastomoses help to protect the brain from ischemia |
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Term
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Definition
| depends on arterial-venous shunting and depends on velocity of blood so during neurosurgery decrease hematocrit to increase blood velocity and decrease shunting to venous circulation |
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Term
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Definition
| very long so resistance depends on length and contribute more in vascular resistance in addition to arterioles |
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Term
| components that needed to be maintained in brain |
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Definition
| 1. blood flow; 2. composition of interstitium; neurons extremely sensitive to ischemia and result in death of an organism and concentration of ions important for functioning of neurons |
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Term
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Definition
| cranial contents surrounded by a rigid structure and overall volume cannot change; an increase in volume of any of the intracranial structures must be accompanied by a decrease in volume of other components (ie in tumor or subdural hematoma); increasing intracranial pressure leads to increase in cerebral vascular resistance and cerebral blood flow goes down so the sympathetics try to increase blood pressure by increasing TPR to compensate for the decrease in cerebral blood flow; increasing cerebral spinal fluid pressure results in an increase in blood pressure but a decrease in heart rate (might be due to barorecptors activating parasympathetics) |
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Term
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Definition
| permeability of most cerebral blood vessels is lower than other areas of the body; primary barrier occurs at the endothelial cells (basal lamina, pericytes, and astrocyte foot processes also contribute); this creates the need for transporters of essential molecules to which endothelial cells are not permeable (glucose) |
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Term
| tight junctions in blood brain barrier |
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Definition
| claudins and high density occludins span the plasma membrane and interact with cells in close proximity forming a seal restricting charged compounds from crossing; these structures are subject to regulatory mechanisms (phosphorylation) changing permeability and accessory molecules and adhesion molecules interact with cytoskeleton |
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Term
| control of cerebral blood flow |
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Definition
| normally receives about 14% of cardiac output and normal VO2 is 3ml/min/100g with an AVO2 difference of 6ml/100ml of blood and if cerebral blood flow is inadequeate oxygen extraction is increased; increasing CO2 produces a pronounced vasodilation and why turn up frequency of ventilator when see edema increasing to increase vascular resistance; K, PGs, and adenosine have been postulated to be mediators of cerebral blood flow |
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Term
| astrocytes role in metabolism and cerebral blood flow |
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Definition
| have long foot processes can contact synapses and contact cerebral blood vessels and have receptors for Glu so increase neuronal activity increase Ca intracellularly and astrocytes can secrete vasodilators and direct communication between metabolic functioning that occurs very quickly |
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Term
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Definition
| cerebral blood flow is well regulated between systemic blood pressure when arterial CO2 is kept constant; with chronic exposure to high blood pressure causes a shift in the autoregulatory curve and more protected against increases in systemic pressure but are more vulnerable to reductions in blood pressure |
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Term
| neuronal control of cerebral blood flow |
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Definition
| innervated by sympathetics and parasympathetics probably not involved in the normal regulation of the cerebral blood flow and alpha adrenergic receptors on cerebral vessels are relatively sparse and insensitive; major function of sympathetic innervation of cerebral vessels appears to be protection against increases in perfusion pressure; gray matter gets about third as much blood flow than white matter and when specific areas of the brain increase their activity blood flow to those areas increase and following acute ischemic period in specific regions the vasculature in that region may lose its autoregulatory ability |
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