Term
| What Level 2 systems comprise the Central Nervous System AKA CNS? |
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Definition
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Term
| If a nerve impulse from a PNS sensory nerve enters the spinal cord and it requires a reflex response, what happens next? |
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Definition
- Spinal cord processes the message and sends out a response via an efferent nerve
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Term
| If a nerve impulse from a PNS sensory nerve enters the spinal cord and it requires interpretation, what happens next? |
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Definition
- Spinal cord relays the message to the brain
- Brain responds
- Spinal cord relays the response from the brain to an efferent nerve
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Term
| What are the functions of the spinal cord? |
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Definition
- Reflex center
- Relays incoming information TO the brain (via ascending tracts)
- Transmits responsive information FROM the brain (via descending tracts)
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Term
| Describe the external anatomy of the spinal cord including basic characteristics and structures |
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Definition
- Oval-shaped and < 2.0cm thick
- Exits the cranial cavity at the foramen magnum
- 15-18 inches long and ends between L1 and L2 in most adults
- Has 31 segments; each of these segments give rise to a pair of spinal nerves
- Has 2 englargements AKA thickenings
- Cervical - site where nerves supplying upper extremities arise
- Lumba: site where nerves supplying the lower extremities arise
- Has a tapered end-point at the inferior end of the spinal cord known as the Conus Medullaris
- Has a group of nerve roots extending below L2 known as the Cauda Equina (horse tail)
- Attaching the Cauda Equina to the superior portion of the coccyx are fibrous CT extensions called Filum Terminale
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Term
| Describe the meninges and it's constituent components |
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Definition
- Meninges: three layers of protective fibrous CT membranes surrounding the spinal cord and continuous with the brain
- Dura Mater: outermost layer; tough, fibrous CT
- Arachnoid Mater: Middle layer; thin
- Pia Mater: innermost layer; very thin, transparent CT that directly adheres to the spinal cord and brain surface
- Has blood vessels and nerves lining external surface
- Denticulate ligaments (delicate extensions of the pia mater) secure the spinal cord to the bony vertebral canal
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Term
| If you were going to perform a spinal tap where would you do it and why? |
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Definition
- At or below L3-L4 to ensure the spinal cord has ended above where you'll be sticking the needle
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Term
| Name and describe the three meningeal spaces |
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Definition
- Epidural space: between bone of the vertebra and the dura mater
- Contains adipose CT and blood vessels (excellent anatomic landmark)
- Epidural block injection is given in this space at L3 (because the spinal cord has definitely ended by that point)
- Subdural space: between the dura mater and arachnoid mater
- thin space filled with serous fluid
- Subarachnoid space: between the arachnoid mater and pia mater
- Wide space; cerebro-spinal fluid AKA CSF circulates through here
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Term
| What is the white matter of the spinal cord? |
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Definition
- White matter is comprise of myelinated nerves, divided into "columns" (anterior AKA ventral, lateral, and posterior AKA dorsal)
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Term
| What is the gray matter of the spinal cord? |
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Definition
- Unmyelinated nerves, differentiated into "horns" by location (anterior, posterior, lateral)
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Term
| In terms of spinal cord anatomy, what is a ganglion and where is it located? |
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Definition
- Ganglion: swelling of a nerve containing a concentration of neurosomas
- In terms of spinal cord anatomy, ganglions are located OUTSIDE the CNS (think of where the dorsal root ganglion is in relation to the spinal cord)
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Term
| What are spinal nerves, where are they located, how many are there, and where do they generally exit the spinal cord? |
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Definition
- Spinal nerve: bundle of nerve fibers (axons)
- Located OUTSIDE the CNS, leading into or away from the spinal cord
- 31 pairs
- Exit the spinal cord at the intervertebral foramen with the exception of the first spinal nerve pair which exits between the skull and the atlas (C1)
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Term
| What is a tract and where would it be located? |
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Definition
- Bundle of nerve fibers (axons) WITHIN the CNS
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Term
| What is the function of an ascending tract (AKA sensory tract) and what are its components? |
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Definition
- Carry impulses from the spinal cord UP to the brain
- Comprised of:
- First-order neuron: a PNS afferent nerve
- Second-order neuron: the ascending tract that transmits the impulse to the brain's thalamus or cerebellum
- Third-order neuron: transmits the impulse from the thalamus to the brain's cerebrum for interpretation
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Term
| What is the function of a descending tract AKA motor tract and what are its components? |
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Definition
- Transmits the responsive message from the brain DOWN the spinal cord
- Comprised of:
- Upper motor neuron AKA UMN: arises within the cerebrum or, less commonly, the brainstem
- Lower motor neuron AKA LMN: arises within the spinal cord's anterior horn or, less commonly, the brainstem
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Term
| What order neuron is the Spinothalamic Tract? |
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Definition
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Term
| What are the anatomic landmarks of the spinal cord's internal anatomy? |
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Definition
- Anterior (ventral) median fissure: deep indentation
- Posterior (dorsal) median sulcus: small groove
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Term
| Describe the spinal cord's gray matter, list its components, and list what those components contain |
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Definition
- H-Shaped, grayish in coloration, unmyelinated nerves
- Components:
- Posterior (dorsal) horn: contains sensory axons and interneurons
- Lateral horn: contains interneurons, tract synapses, and cell bodies of preganglionic sympathetic neurons
- Anterior (ventral) horn: contains motor cell bodies and dendrites
- Gray commisure: connects R and L sides of the gray matter
- Has a central canal in the center of it, filled with CSF; open in young children but collapsed in most areas of an adult
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Term
| Describe the spinal cord's white matter and its components as well as what they contain |
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Definition
- External to gray matter, myelinated nerves
- Components:
- Posterior (dorsal) column
- Lateral column
- Anterior (ventral) column
- All three columns contain myelinated tracts
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Term
| Describe a spinal nerve, then name and describe its components |
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Definition
- Spinal nerve contains both sensory and motor axons
- Comprised of:
- Posterior (dorsal) root ganglion: contains sensory cell bodies
- Posterior (dorsal) root and rootlets: contains sensory axons
- Anterior (ventral) root and rootlets: contains motor axons
- Lateral to the spinal nerve it branches to form:
- Meningeal branch: innevates the meninges, vertebrae, and spinal ligaments with sensory and motor fibers
- Posterior (dorsal) ramus: innervates the skin and muscles and joints of the back (in that region of the spinal cord) with sensory and motor fibers
- Anterior (ventral) ramus: innervates the anterior and lateral skin and muscles of the trunk (in that region of the spinal cord) with sensory and motor fibers; gives rise to nerves of the limbs (via a plexus)
- Anterior ramus branches to form a pair of communicating rami
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Term
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Definition
| Routes followed by nerve impulses as they travel throughout the Nervous system |
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Term
| What is a reflex arc and what are its components? |
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Definition
- The simplest nerve pathway; constitutes the structural and functional basis for a reflex (an involuntary response to a change/stimulus of a physical, chemical, internal, or external nature)
- A reflex arc's components are:
- Receptor: stimulated by a change AKA stimulus
- Sensory neuron: transmits incomping impulse from the PNS to the CNS
- Integration center: composed of interneurons functioning as the processing center within the CNS
- Motor neuron: transmits the response impulse from the CNS to effectors
- Effectors: muscles or glands
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Term
| Why would one test a reflex to determine the status of the nervous system? |
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Definition
| Normal reflexes depend on nurmal neuron functions and pathways; if the system isn't functioning properly, the reflex will exhibit abnormalcy |
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Term
| What is a plexus and what does it contain? |
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Definition
- A plexus is a complex formed from the merging of several spinal nerve ventral branches
- NOTE: Except within the thoracic region
- Each plexus contains fibers from different spinal nerves, those spinal nerve fibers are carried to the body's periphery via several different branches, which allows an effector to be innervated by more than one spinal nerve
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Term
| What are Dermatomes and why are they useful? |
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Definition
- Sensory nerve fibers for a particular spinal nerve innervating a specific area/region of skin
- Useful for localizing injuries to PNS sensory nerves, dorsal root, dorsal root ganglion, and/or dorsal horn
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Term
| What are the general characteristics of the brain, including its regions? |
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Definition
- Mushroom-shaped, gelatinous-like structure within the cranial cavity
- Weighs approximately 3.0 lbs
- Consists of 75% water
- Has 100 billion neurons
- Gray matter (unmyelinated nerves) is external while white matter (myelinated nerves) is internal
- NOTE: This is the reverse of the arrangement in the spinal cord
- Uses 20% of the body's O2 and is unable to store glucose, thus requiring a constant supply of both
- A safety mechanism exists: blood vessels supplying the brain can only constrict if O2 levels are too high
- Has four regions:
- Brainstem
- Cerebellum (anatomic landmark: always posterior and inferior)
- Cerebrum
- Diencephalon
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Term
| Describe the meninges and meningeal space arrangement as related to the brain and cranial cavity (NOTE: not the same as with spinal cord) |
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Definition
- Meninges surrounding the brain are continuous with the spinal cord's meninges
- Comprised of:
- Dura Mater: outer layer, attached to cranial bones
- NO epidural space
- Subdural space: between dura and arachnoid mater; thin; no CSF
- Arachnoid mater: middle layer
- Subarachnoid space: between arachnoid and pia mater; wide; has CSF
- Pia mater: innermost layer; directly covers the brain
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Term
| Describe the structure and function of the blood supply to the brain |
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Definition
- Capillaries supplying the brain are made of modified, dense, tightly-packed endothelial cells surrounded by astrocyte foot processes that form a selectively permeable wall (blood-brain barrier AKA BBB)
- Fat and water soluble molecules pass through the BBB (including: Ethyl alcohol, O2, CO2, glucose, caffeine, nicotine, general anesthetics)
- Ions (Na+, K+, Cl-) and some waste products (urea and creatinine) can't pass through the BB without some type of assistance via facilitated diffusion or active transport
- Large proteins, toxins, and most drugs (antibiotics, anti-cancer drugs) cannot penetrate the BBB
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Term
| Describe the general characteristics and structures of the cerebrum |
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Definition
- The largest and most complex region of the brain
- Two hemispheres (R/L) that mirror each other; separated by a longitudinal fissure
- Each hemisphere is subdivided into 5 lobes, 4 of which are named after the overlying cranial bone (frontal, parietal, occipital, temporal, and insula - deep to the temporal lobe).
- Each hemisphere has: cerebral cortex, white matter, basal nuclei
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Term
| Describe the characteristics, structures, and functions of the cerebral cortex |
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Definition
- Cerebral cortex is 2-3mm outermost portion of the brain; gray matter
- Contains 75% of all the CNS cell bodies, dendrites, and unmyelinated axons (14-16 billion neurons)
- Convulted via gyri (raised ridges), sulci (shallow grooves) separating gyri, and fissure (deep groove separating hemispheres and brain regions
- Functionally: cerebral cortex is the core site of all qualities associated with conscious behavior or consciousness (ability to communicate, remember, perceive, understand, judge, appreciate, initiate voluntary movements)
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Term
| Describe the characteristics, structures, and functions of white matter of the cerebral cortex |
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Definition
- Deep to the cerebral cortex; has myelinated fibers (axons) bundled into tracts
- Association fibers: link gyri of the same hemisphere
- Commisural fibers: link an area of one hemisphere to the corresponding area of the opposite hemisphere
- Corpus Callosum is the largest commisure, located superior to the lateral ventricles
- Projection fibers: link the cerebrum to other brain regions or to the spinal cord
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Term
| Describe the characteristics, functions, and structures of basal nuclei |
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Definition
- Mass of gray matter: caudate nucleus and lentiform nucleus (putamen and globus pallidus) deep within each hemisphere
- Acts to control and coordinate automatic skeletal muscle movements and muscle tone
- Produces a skeletal muscle inhibitory neurotransmitter: dopamine
- disturbances of the basal nuclei result in abnormal movement disorders such as Parkinson's disease or Huntington's chorea
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Term
| How many known functional areas exist in the cerebral cortex? |
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Definition
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Term
| What are the functional areas of the frontal lobe of the cerebral cortex? |
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Definition
- Primary (1°) Motor Cortex AKA Precentral Gyrus:
- Anterior to the central sulcus (anatomic landmark on a frontal plane)
- It controls contralateral voluntary motor functions (right primary motor cortex controls skeletal muscles on the left side and vice versa)
- Motor Association Area:
- Anterior to the Primary Motor Cortex
- Controls and is the memory bank for skilled motor activities of a repetitious nature (texting, playing an instrument)
- Prefrontal Cortex
- Anterior to the Motor Association Area
- COntrols and is the memory bank for concentration, planning, problem solving, and emotions related to personal and social itneractions
- This was the site of a lobotomy to make patients more 'docile'
- Broca's Area
- Usually anterior to the inferior left primary motor cortex
- Controls muscles of speech production
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Term
| What are the functional areas of the parietal lobe of the cerebral cortex? |
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Definition
- Primary (1°) Somatosensory Cortex AKA Postcentral Gyrus
- Posterior to the central sulcus
- Interprets contralateral conscious awareness of sensations (in the skin) and proprioception (position sense) from skeletal muscles, joints, and tendons (i.e. the right primary somatosensory cortex interprets sensation and position sense from the left side of the body and vice versa)
- Somatosensory association area
- Posterior to the Primary Somatosensory Cortex
- Integrates sensory input to allow an understanding of an object felt (size, texture, etc)
- Wenicke's Area AKA General Interpretation Area
- Usually at the posterior-superior border of the Left temporal lobe
- Important for both language comprehension and choosing the words to speak
- Injury to this area affects one's ability to interpret the situation that one is in
- Clinical Dx known as "imbecile"
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Term
| What functional areas does the temporal lobe of the cerebral cortex contain? |
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Definition
| Primary and association areas for olfactory (smell) and auditory (sound) stimuli |
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Term
| What functional areas are found in the occipital lobe of the cerebral cortex? |
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Definition
| Primary and association areas for visual stimuli |
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Term
| What functional areas are found in the insula lobe of the cerebral cortex? |
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Definition
| Primary and association areas for gustatory (taste) and olfactory (smell) stimuli |
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Term
| What is hemisphere dominance and what are the dominances exhibited by each hemisphere? |
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Definition
- While both hemispheres are capable of performing certain similar or same functions, one hemisphere usually asserts more control (AKA is dominant)
- Left Hemisphere exhibits dominance for: language, science, math, logic, right side voluntary muscle control
- Right hemisphere exhibits dominance for: emotions, art, music, imagination, left side voluntary muscle control
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Term
| Describe the structure and function of the limbic system |
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Definition
- Complex, ring-like structure on the medial side of each cerebral hemisphere (limbus = ring)
- It is the 'emotional' brain and is involved with memory
- Two key structures of the limbic system:
- Hippocampus - plays a major role in memory
- Amygdala - aversion center for the identification of fear or danger
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Term
| What is the diencephalon and of what does it consist? |
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Definition
- Region between the brainstem and the cerebrum
- Consists of: Thalamus, Hypothalamus, and Epithalamus
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Term
| Describe the structure and function of the thalamus |
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Definition
- Egg-shaped mas in the center of the cranial cavity
- 2 masses, one Right, one Left
- Comprises 80% of the Diencephalon
- Intermediate mass AKA interthalamic adhesion: commisure of gray matter joining R and L thalamus in about 70% of people
- Primary function: major relay station for ascending sensory impulses which are sent to the cerebral cortex for conscious interpretation; all 2nd order sensory nerve impulses EXCEPT sense of smell synapse in the thalamaus
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Term
| Describe the structures and functions of the hypothalamus |
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Definition
- About the size of a lump of sugar; inferior and slightly anterior to the thalamus; posterior wall borders paired mamillary bodies (relay stations from olfactory pathways and the limbic system)
- Pituitary stalk AKA infundibulum: connects the hypothalamus to the pituitary gland
- Functions: consists of many nuclei (see fig 14.12) that maintain homeostasis by regulating visceral activities and it serves as a link between the nervous system and endocrine system; considered the body's Master Endocrine Gland
- Regulates ANS activity: HR, BP, respiration rate
- Regulates emotional responses: perceptions of emotions, sex drive
- Regulates body temperature: internal thermostate, initiates sweating or shivering
- Regulates food intake: initiates feelings of hunger or satiation
- Regulates water balance and thirst
- Regulates sleep-wake cycle
- Controls many endocrine system functions including production of releasing and inhibiting hormones that regulate anterior pituitary gland; produces ADH and Oxytocin that are stored and released from posterior pituitary gland
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Term
| Describe the location, structure, and function of the Epithalamus |
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Definition
- Superior 'roof' of the diencephalon (a top hat for your thalamus!)
- Pineal gland AKA pineal body: extends from posterior border
- secretes melatonin: mood regulator that causes drowsiness
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Term
| Describe the general characteristics and functions of the brainstem |
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Definition
- Described as the stalk of the brain
- Continuous with the diencephalon superiorly and spinal cord inferiorly
- Relays messages between the spinal cord and other brain regions
- Consists of 3 segments (each approx 1 inch long) and a formation
- Medulla Oblongata
- Pons
- Midbrain
- Reticular Formation
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Term
| Describe the characteristics, structure, and function of the medulla oblongata: |
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Definition
- Enlarged continuation of the spinal cord
- Extends superior from the foramen magnum for approximately one inch
- Relay station between brain and spinal cord; all ascending and descending tracts pass through it; site of crossing-over of motor tracts AKA decussation of pyramids
- This decussation is what causes contralateral cerebral cortex control of voluntary muscles
- Site of three vital visceral control centers
- Cardiac center: increase or decrease heart rate
- Vasomotor center: controls smooth muscle in vessel walls
- Respiratory center: regulates rate, rhythm, depth of breathing by working in conjunction with the respiratory center in the Pons
- NOTE: injury to any vital centers results in death
- Also contains: vomiting, hiccuping, swallowing, coughing, sneezing centers
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Term
| Describe the characteristics and functions of the Pons |
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Definition
- Rounded bulge located ventrally between the medulla oblongata and the midbrain
- Has respiratory center: regulates rate, rhythm, depth of breathing in conjunction w/ respiratory center in medulla oblongata
- Contains tracts that bridge the spinal cord to the brain and parts of the brain to each other
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Term
| Describe the characteristics and functions of the midbrain |
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Definition
- Superior and posterior to the pons
- Joins the lower brainstem and spinal cord to higher parts of the brain
- Separated into an anterior and posterior portion by the cerebral aqueduct which connects the 3rd and 4th ventricle
- Posterior to the cerebral aqueduct there are 4 'bumps' known as the corpora quadragemina. Each side of the brain has:
- a superior colliculus: visual reflex center
- an inferior colliculus: audio reflex center
- Anterior to the cerebral aqueduct is the cerebral peduncle
- Verticle pillar that seems to support the cerebrum
- Contains pairs of motor tract bundles
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Term
| Describe the characteristics and functions of the reticular formation |
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Definition
- More than 100 networks of gray matter neurons deep within all levels of the brainstem
- Long axons interconnect with other brain regions to keep the brain activated and aroused
- Known as the reticular activating system/RAS
- Damage to RAS results in a coma
- RAS actas a sensory filter: weak, familiar, repetitive impulses are filtered out while strong, unusual, or significant impulses are allowed to reach consciousness
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Term
| Describe the characteristics, structures, and functions of the cerebellum |
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Definition
- Posterior-inferior region of the brain
- Cerebellar cortex: thin outer layer of gray matter
- Arbor vitae: branched white matter deep to the cortex
- Vermis: midline posterior portion connecting each hemisphere
- Function: is a comparator; compares intended complex skeletal muscle movements and position with what is actually happening in order to smooth and coordinate movements; involved with balance, posture, and coordination
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Term
| What are ventricles? List the ventricles and give their locations and significant structural details |
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Definition
- A series of 4 interconnected cavities within the cerebral hemispheres and brainstem
- 2 large lateral ventricles: within cerebral hemispheres below the corpus callosum and separated by the septum pellucidum; these connect to
- 3rd ventricle: brain's midline, intermediate to the b/l thalamus; cerebral aqueduct connects to
- 4th ventricle: in the brainstem anterior to the cerebellum; has extensions with openings that lead into the subarachnoid space of the brain and spinal cord, continuous with the spinal cord's central canal
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Term
| What is Cerebro-Spinal Fluid (CSF) and what are its functions? |
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Definition
- 100-160ml of ultra-filtrate of blood
- Replaced every 3-4 hours
- Completely surrounds/bathes the brain and spinal cord
- Contains more Na+ and Cl- with less protein, Ca++, and K+ than other ECFs
- Functions:
- Maintains the chemical envinronment of the CNS
- Physical protection: buoys the CNS and acts as shockproofing (remember your physics)
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Term
| Describe how CSF is originated, circulated, and removed |
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Definition
- Ependymal cells (cuboidal-like epithelium) line the ventricles and connect with the pia mater to form a choroid plexus (mass of specialized capilaries)
- The choroid plexus of each lateral ventricle filtrates blood, forming CSF, which passes down to the 3rd ventricle where more CSF is added by that ventricle's choroid plexus
- CSF passes through the cerebral aqueduct to the 4th ventricle where more CSF is added by that ventricle's choroid plexus
- CSF then enters the subarachnoid space surrounding the brain (filling it from posterior to superior) and the subarachnoid space surrounding the spinal cord
- CSF flows down the posterior side of the cord, around the inferior tip, up the anterior side of the cord, around the subarachnoid space of the anterior portion of the brain, filling the space
- CSF exits through arachnoid villi, sponge-like folds with pressure-sensitive valves to permit one-way flow of the CSF into the dural sinus, which drains venous blood from the brain
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Term
| How many peripheral nerves are associated with the brain? |
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Definition
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Term
| Describe the characteristics of the first two pairs of cranial nerves |
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Definition
- 1st Pair: Olfactory nerve
- Fibers originate as receptors lining the nasal cavity and synapse in the primary olfactory cortex of the cerebrum (insula and temporal lobes)
- 2nd Pair: Optic nerve
- Fibers originate in retina, pass through the optic canal, converge to form the optic chiasm (where fibers partially cross-over), and continue on as optic tracts which synapse in the thalamus
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Term
| Where do Cranial Nerve pairs 3 through 12 originate? |
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Definition
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Term
| What anatomical structures do the cranial nerves serve? |
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Definition
- Head and neck structures only
- EXCEPT: Cranial Nerve 10 - the Vagus nerve, which enters the thoracic and abdominal cavities supplying visceral organs in these areas with sensory input and motor parasympathetic output
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Term
| Describe Alzheimer's Disease |
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Definition
- Progressive, degenerative disease of the brain
- Characterized by dementia and cognitive deficits such as memory loss, disorientation, moodiness, confusion, and hallucinations
- Neurofibrillar tangles (twisted neurofibrils within nerve cell bodies), senile plaques (like shrapnel between neurons), and atrophied gyri are discoverable upon autopsy
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Term
| Describe a Cerebrovascular Accident AKA CVA AKA Stroke |
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Definition
- Decreased blood supply to the brain due to h emorrhage or an obstruction (embolus or clot) results in irreversible brain damage if oxygen is deprived for more than 3>5 minutes
- 80% of CVA patients die during the initial attack
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Term
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Definition
- Problems with the brain's organizational patterns
- One has trouble translating eye and/or ear input into an understandable language
- Result is one perceives input but it is interpreted as upside down or backwards
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Term
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Definition
- CSF is not drained and accumulates in the skull
- Causes an enlarged skull with increased pressure on the brain
- Treatment is the insertion of a shunt that drains excess CSF into a neck vein
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Term
| Describe Multiple Sclerosis AKA MS |
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Definition
- Characterized by a gradual loss of the myelin sheath in the CNS
- This results in deterioration and wasting of nerves and muscles
- Autoimmune disease, possibly triggered by a viral infection
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Term
| Describe paralysis (in general) and both subtypes of paralysis |
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Definition
- Motor function loss secondary to a damaged brain, spinal cord, or motor neurons
- Flaccid Paralysis: a lower motor neuron disease due to damaged motor neurons in the spinal cord's anterior horn or peripherally
- The efferent nerve impulse does not reach a muscle, resulting in lack of movement and subsequent atrophy
- Spastic paralysis: an uper motor neuron disease due to damage of the cerebrum's primary motor cortex
- Muscles can still be stimulated to contract via spinal reflexes, which leaves muscle tissue healthy, but there is a loss of voluntary muscle control, causing involuntary spasms
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Term
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Definition
- Sensory loss or abnormalcies due to damaged sensory neurons in the spinal cord or peripherally
- Includes sensations of tingling, pins-and-needles, prickling, burning and/or numbness (no sensation)
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Term
| Describe Parkinson's Disease |
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Definition
- Decreased dopamine production by basal nuclei results in:
- Increased skeletal muscle abnormal movements (tremors; shakes)
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Term
| Describe poliomyelitis AKA Polio |
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Definition
- A viral infection of the spinal cord's anterior horn
- Results in destruction of motor cell bodies, which leads to flaccid paralysis
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Term
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Definition
- Amputees have chronic pain in an amputated/nonexistent limb or digit, possibly due to cut sensory nerve continuing to respond to the trauma of amputation
- The nerve sends signals to the brain which the brain interprets as painful stimuli coming from the missing limb or digit
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Term
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Definition
- Pain arising from a visceral organ perceived to be somatic in origin
- Due to visceral and somatic afferent pain nerve fibers traveling along the same pathways and sharing the same dorsal root ganglia entrance into the spinal cord, it is possible for the interneurons or tract synapses in the lateral horn to become confused and 'guess' which sensory nerve brought the message
- Example of this is pain in the left arm being perceived during a heart attack due to spinal segments T-1 through T-5 innervating the visceral heart plus somatic skeletal muscles in the medial left arm
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Term
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Definition
- One or more vertebrae do not form the posterior vertebral arch
- The result is the spinal cord and/or meninges protrude externally
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