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Final

PSL300H1 Study Guide - Final Guide: Semicircular Canals, Eustachian Tube, Membranous Labyrinth

by

Department
Physiology
Course Code
PSL300H1
Professor
Doug Mac Kay
Study Guide
Final

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ANATOMY OF THE EAR
EQUILIBRIUM motion of head and tilt
sense of equilibrium detects motion of head and its tilt relative to gravity
get info abt these from many senses proprioception and vision.
vestibular apparatus also know as membranous labyrinth
vestibular apparatus: set of fluid-filled chambers.
semicircular canals: cristae sense rotational acceleration.
2 otolith organs: utricle and saccule, each have maculae which senses head's tilt and translational
acceleration (motion and relative position in space).
3 orthogonal canals for 3 dimensions of head rotation:
horizonal canal senses side to side rotation (shaking head in "no" motion), superior and posterior
sense up and down nodding eat-to-shoulder tilt. each canal filled with endolymph, ends in bulge
(ampulla), containing its crista.
crista contains mechanreceptors hair cells , each have stereocilia in apical membrane. cilia extends
into cupula (gelatinous mass), seals off into canal. head turns endolymph lags and pushes on cupula
hairs bend (if head swings right, endolymph pushes hair to left). when hair cells move, either inhibited or
excited.
each vesitbular hair cell has on long stereocilium: the kinocilium. each hair cell has directionality bcs
oriented twrds the kinocillium. if hair bends twds kinocilium hair cell depolarized NT released
sensory neuron activated. if they bend away they hyperpolarize.
tiplinks: connect stereocilia. when they open up, ion channels open.
hair cells = tonically active. release NT onto primary sensory neurons.
lag of endolymph reflects change in head rotation: constant speed after 20 s no endolymph lag., cupula +
hairs return to rest position.
if head stop abruptly fluid built up momentum and can't stop immediately pushes cupula in opposite
direction.
in maculae hair cells extend stereocilia into gelationous otolith membrane. otoliths = calcium carbonate
and protein particles on membrane surface. gravity/acceleration moves otoliths, membrane moves with
them, hairs bend. when head upright, macula of utricle = horizontal, saccule = vertical.
equilibrium pathways project to cerebellum mantain posture and sense of space and balance.
hair cells activate primary sensory neurons on vestibular nerve (CN VIII) those neurons pass directly to
cerebellum or synapse in medulla, proceed to cerebellum or up through reticular formation and thalamus to
cortex.
vestibular apparatus
external ear
pinna
ear canal
tympanic membrane
cochlea
Eustachian tube
middle ear
inner ear
membranous labyrinth
cristae
hair cells
semicircular canals and head
rotation
otolith organs and tilt
utricle, saccule, maculae
orthogonal canals:
posterior, horizontal and
superior
endolymph
ampulla
stereocilia
cupulla
kinocilium
tiplinks
sound waves
external ear pinna, ear canal, sealed by tympanic membrane
(eardrum)
middle ear air filled space connected to pharynx by Eustachian tube
inner ear sensors: vestibular apparatus for equilibrium, cochlea for
hearing
EQUILIBRIUM AND HEARING
May-27-136:01 PM
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