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| 3 Major Parts of the Brain |
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| cerebrum, cerebellum, brainstem |
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| contains 50% of the neurons; second largest brain region, located in posterior cranial fossa; about 10% of brain volume; marked by gyri, sulci, and fissures |
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| the portion of the brain that remains if the cerebrum and cerebellum are removed; diencephalon, midbrain, pons, and medulla oblongata |
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the seat of neuron cell bodies, dendrites, and synapses
dull white color when fresh, due to little myelin
forms surface layer, cortex, over cerebrum and cerebellum
forms nuclei deep within brain |
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bundles of axons; lies deep to cortical gray matter, opposite relationship in the spinal cord, pearly white color from myelin around nerve fibers
composed of tracts, bundles of axons, that connect one part of the brain to another, and to the spinal cord |
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| deep groove that separates cerebral hemispheres |
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| thick nerve bundle at bottom of longitudinal fissure that connects hemispheres |
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| voluntary motor functions; motivation, foresight, planning, memory, mood, emotion, social judgment, and aggression |
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| receives and integrates general sensory information, taste and some visual processing |
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| primary visual center of brain |
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| areas for hearing, smell, learning, memory, and some aspects of vision and emotion |
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| insula (hidden by other regions) |
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| understanding spoken language, taste and sensory information from visceral receptors |
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| three pairs of stalks that connect the cerebellum to the brainstem |
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| functions of the cerebellum |
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*monitors muscle contractions and aids in motor coordination
*evaluation of sensory input
*comparing textures without looking at them
*spatial perception and comprehension of different views of *3D objects belonging to the same object
*timekeeping center
*predicting movement of objects
*helps predict how much the eyes must move in order to *compensate for head movements and remain fixed on an object
*hearing
*distinguish pitch and similar sounding words
*planning and scheduling tasks
*lesions may result in emotional overreactions and trouble with impulse control |
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| Falx cerebri, Falx cerebelli, Tentorium cerebelli |
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| separate the two cerebral hemispheres |
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| separate the two cerebellar hemispheres |
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| separate the cerebrum from the cerebellum |
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three connective tissue membranes that envelop the brain
*lies between the nervous tissue and bone
*as in spinal cord, they are the dura mater, arachnoid mater, and the pia mater
*protect the brain and provide structural framework for its arteries and veins |
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in cranial cavity - 2 layers
*outer periosteal – equivalent to periosteum of cranial bones
*inner meningeal – continues into vertebral canal and forms *dural sac around spinal cord
*cranial dura mater is pressed closely against cranial bones
*no epidural space
*layers separated by dural sinuses – collect blood circulating through brain |
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*transparent membrane over brain surface
*subarachnoid space separates it from pia mater below
*subdural space separates it from dura mater above in some places |
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*very thin membrane that follows contours of brain, even dipping into sulci
*not usually visible without a microscope |
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*inflammation of the meninges
*serious disease of infancy & childhood
*especially between 3 months and 2 years of age
*caused by bacterial and virus invasion of the CNS by way of the no
*diagnosed by examining the CSF for bacteria
*lumbar puncture (spinal tap) draws fluid from subarachnoid space between two lumbar vertebraese and throat
*pia mater and arachnoid are most often affected
*bacterial meningitis can cause swelling the brain, enlarging the ventricles, and hemorrhage
*signs include high fever, stiff neck, drowsiness, and intense headache and may progress to coma – death within hours of onset |
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*four internal chambers within the brain
*two lateral one in each cerebral hemisphere
*interventricular foramen- a tiny pore that connects to third ventricle
*third- single narrow medial space beneath corpus callosum
cerebral aqueduct runs through midbrain and connects third to fourth ventricle
*fourth – small triangular chamber between pons and cerebellum
*connects to central canal runs down through spinal cord |
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| spongy mass of blood capillaries on the floor of each ventricle |
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| neuroglia that lines the ventricles and covers choroid plexus; produces cerebrospinal fluid |
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| cerebrospinal fluid (CSF) |
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*clear, colorless liquid that fills the ventricles and canals of CNS
*bathes its external surface
*brain produces and absorbs 500 mL/day
100 – 160 mL normally present at one time
*production begins with the filtration of blood plasma through the capillaries of the brain
*ependymal cells modify the filtrate, so CSF has more sodium and chloride than plasma, but less potassium, calcium, glucose, and very little protein |
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| functions of cerebrospinal fluid |
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| buoyancy, protection, chemical stability |
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*cardiac center
-adjusts rate and force of heart
*vasomotor center
-adjusts blood vessel diameter
*respiratory centers
-control rate and depth of breathing
*reflex centers
-for coughing, sneezing, gagging, swallowing, vomiting, salivation, sweating, movements of tongue and head |
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*ascending sensory tracts
*descending motor tracts
*pathways in and out of cerebellum
*cranial nerves V, VI, VII, and VIII
*sensory roles – hearing, equilibrium, taste, facial sensations
*motor roles – eye movement, facial expressions, chewing, swallowing, urination, and secretion of saliva and tears
*Also helps control sleep, respiration, and posture |
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*short segment of brainstem that connects the hindbrain to the forebrain
*contains the motor nuclei of two cranial nerves that control eye movements – CN III and CN IV
*tectum – roof-like part of the midbrain posterior to cerebral aqueduct
*exhibits four bulges, the corpora quadrigemina
upper pair, the superior colliculi function in visual attention, tracking moving objects, and some reflexes
*lower pair, the inferior colliculi receives signals from the inner ear
*relays them to other parts of the brain, especially the thalamus
*Function in startle reflex
*cerebral peduncles – two stalks of descending motor axons that conduct impulses from motor neurons in cerebral cortex to midbrain. |
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| loosely organized web of gray matter that runs vertically through all levels of the brainstem |
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*the diencephalon encloses the third ventricle
*most rostral part of the brainstem
*has three major embryonic derivatives
-thalamus
-hypothalamus
-epithalamus |
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Cranial Nerve I (sensory)
-sense of smell
-damage causes impaired sense of smell |
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Cranial Nerve II (sensory)
-provides vision
-damage causes blindness in part or all of the visual field
-occipital lobe is primarily responsible
-50% contralateral control, 50% ipsilateral control
-rods (gray) vs cones (color) |
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Cranial Nerve III (motor)
-controls muscles that turn the eyeball up, down, & medially as well as controlling the iris, lens, & upper eye lid
-damage causes drooping eyelid, dialated pupil, double-vision, difficulty focusing & inability to move eye in certain directions
-rectus muscles move eye left, right, up & down
**Diplopia- double-vision |
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Cranial Nerve IV (motor)
-controls eye movement medially (superior oblique muscle)
-damage causes double-vision & inability to rotate eye inferolaterally |
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Cranial Nerve V (mixed)
-largest of the cranial nerves
-most important sensory nerve on the face
-forks into 3 divisions
*opthalmic division (V1) sensory
*maxillary division (V2) sensory
*mandibular division (V3) mixed |
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Cranial Nerve VI (motor)
-provides eye movement laterally
-damage results in inability to rotate eye laterally & at rest eye rotates medially |
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Cranial Nerve VII (mixed)
-Motor: major motor nerve of facial muscles; facial expressions, salivary glands, tear, nasal, & palatine glands
-Sensory: taste on anterior 2/3 of tongue
-damage produces sagging facial muscles & disturbed sense of taste (NO SWEET OR SALTY)
-5 branches of facial nerve
*temporal, zygomatic, buccal, mandibular, & cervical |
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Cranial Nerve VIII (sensory)
-nerve of hearing equilibrium
-damage produces deafness, dizziness, nausea, loss of balance & nystagmus (involuntary rhythms oscillation of the eyes from side to side |
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Cranial Nerve IX (mixed)
-swallowing, salivation, gagging, control of BP & respiration
-sensations from posterior 1/3 of tongue
-damage results in loss of bitter & sour taste, impaired swallowing |
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Cranial Nerve X (mixed)
-most extensive distribution of any cranial nerve
-major role in the control of cardiac, pulmonary, digestive, & urinary function
-swallowing, speech, regulation of viscera
-damage causes hoarseness or loss of voice, impaired swallowing & fatal if both are cut
"EVERYTHING HAPPENS IN VEGAS" |
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Cranial Nerve XI (motor)
-swallowing, head, neck, & shoulder movement
-damage causes impaired head, neck & shoulder movement; head turns towards injured side |
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Cranial Nerve XII (motor)
-tongue movements for speech, food manipulation & swallowing
-if both are damaged- cannot portrude tongue
-if one side is damaged- tongue deviates towards injured side; see ipsilateral atrophy |
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| begin in nuclei of brainstem & lead to glands & muscles |
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| begin in receptors located mainly in head & neck, lead mainly to the brainstem |
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| Cranial Nerve 5 Disorder Trigeminal Neuroglia (tic douloureux) |
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-recurring episodes of intense stabbing pain in trigeminal nerve area (near mouth or nose)
-pain triggered by touch, drinking, washing face
-cause unknown
-no change in nerve structure
-most common in females over 50
-treatment may require cutting nerve |
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-degenerative disorder of facial nerve causes paralysis of facial muscles on one side
-when CN VII becomes injured or stops working
-may appear abruptly with full recovery within 3-5 months
-signs include: drooping of one side of the face, inability to open or close the eyelid, & drooling from one side of the mouth
-affects 40,000 people yearly
-caused by swelling of the nerve which is usually in response to viral infection, such as herpes HSV |
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