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BIOL 4370 (20)
Lecture

Nov. 7th

4 Pages
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Department
Biology
Course
BIOL 4370
Professor
Dr.o'shaughnessy
Semester
Fall

Description
th Nov. 7 • All 3-d movements can be broken into 3 components, x, y and z - vestibular system detects, linear disposition, rotational disposition, and tilt • semi-circular canals are perpendicular to each other (doesn’t matter that they are not in “cardinal planes” because they are perpendicular to each other and brain infers planes relative to each other ie. Changing the definition of x, y and z) • utricle and saccule both detect linear acceleration and tilt - hair cells have stereocillia that go from shorter to longer and are embedded in otolithic membrane membrane (which contains crystals at top called otoconia) - in saccular (imaginary) striola is midline and longest end of steriocila point away from it (saccula is in saggital plane) - in utricle longest end of steriocilia point towards midline (utricle is in horizontal plane) - otoconia add mass (inertia) to the otolithic membrane • vestibular labyrinth is made up of bones of semi circular canals, and utricle and sacccule - all contain endolymph - receptor cells are hair cells which send signals to axons which make up 8 cranial nerve (cell bodies are in scarpa’s ganglion) • Firing rate of vestibular nerve axon in excitatory in one direction and inhibitory in the opposite direction - adaption occurs - tip link has motor which climbs up steriocillia which opens ion channels - tip link motor is inhibited by Calcium - transduction: tip link has tension, opens K/Ca channel, depolarization - but Ca concentration get higher and the motor causes a reduce in tension which causes ion channels to start closing (adaptation) • Semicircular canals have bulge called ampula which contains cupula and endolymph - has hair cells in crista - angular movement (rotation) causes cupula to go from straight to either left or right - in vestibular axon transduction (on response) causes spike, but adaptation occurs, and off response has inhibitory response an then adaptation back to baseline • Much easier to read when you move your head rather than when you move the page - vestibule ocular reflex (VOR): eyes move equal and opposite to head - extra-ocular muscles: lateral and medial rectus; pull eyeball - if you turn head to left, depolarizes hair cells in left semicircular cell (release glutamate onto axons which have cell bodies which enter medulla at vestibular nucleus). - axons in vestibular nucleus decussate and ascend to RIGHT pons at abducens nucleus which sends axons (through cranial nerve 6: abducens nerve) to RIGHT lateral rectus muscle and releases acetylcholine (causes muscle to contract). if acceleration is more rapid, more depolarization occurs in hair cells, and this leads to more acetylcholine - other axons in abducens nucleus decussate (at medial longitudinal fasciculus) to the LEFT oculomotor nucleus which send axons (through 3 cranial nerve: oculomotor nerve) to LEFT eye at medial rectus and release acetylcholine which causes muscle to contract • Vestibular disorders - oscillopsia: world oscillates and world becomes blurred - benign paroxysmal positional vertigo (BPPV): caused by otoconia getting dislodged; results in dizziness in certain head positions. Has cure: - positional alcohol nystagmus: alcohol enters cupula, making it less dense than the endolymph making it buoyant. Ie. Balloon in air vs balloon in water (with alcohol) • Upper motor neuron: neuron that controls movement but doesn’t go to muscle - pre motor cortex (area 6) is 6 times larger in humans than other animals. It’s in charge of planning and executing complex motor tasks (apraxia is loss of this) - primary motor cortex has h
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