auditory

Question 1

audition

Answer 1

-transduce sound waves into electrical energy
-sound waves carry noise
-waves- increases (compression) and decreases (decompression) in pressure -> expressed as decibels
-sound frequency measured in hertz

Question 2

strucutre of ear

Answer 2

-external ear- pinna, external auditory meatus (canal), ends at TM
-middle (air)- TM, auditory ossicles (malleolus, incus, stapes), oval window
-ossicles transport sound waves that hit TM through lever system -> press against oval window and transmit sound wave into water wave in cochlea
-inner ear- cochlea

Question 3

cochlea

Answer 3

-has auditory receptors -> organ or corti
-three sections:
-scala vestbuli- perilymph
-scala media- endolymph - high K -> organ of corti is in here
-scala tympani- perilymph

Question 4

organ of corti

Answer 4

-in the scala media
-in the endolymph (high K)
-auditory receptors are here
-hairs attached to tectorial membrane (stationary)
-basilar membrane (across from tectorial) moves back and forth comparative to tectorial membrane when the TM is moving do to sound waves -> water waves
-movement of basilar membrane moves the hair cells on the tectorial membrane -> bending of hair cells -> increase conductance of K+ in hair cell membrane -> K depolarizes hair cell -> release glutamate -> glutamate binds to cochlear nerves -> action potential
-goes to the afferent cochlear nerves!

Question 5

encoding of sound

Answer 5

-basilar membrane at base of cochlea is stiff -> only responds to high frequency
-basilar membrane at the end of cochlea -> responds to low frequency sounds
-tonotopic map spatial mapping of frequencies that we are hearing

Question 6

auditory pathway

Answer 6

-information -> hair cells of organ of corti -> afferent cochlear nerves ->synapse on dorsal and ventral cochlear nuclei
-SOME cross to lateral lemniscus -> inferior colliculus -> medial geniculate nucleus of thalamus -> auditory cortex
-bc some cross and some dont if you have a lesion centrally -> does not cause deafness
-if you have damage to cochlea it will affect ipsilateral side

Question 7

vestibular system

Answer 7

-equilibrium and balance
-stable visual image for retina
-3 semiciruclar canals- angular and acceleration of the head
-semicircular canals are perpendicular and have ampulla at the end -> have hair cells in cupula
-utricle and saccule- linear acceleration and gravitations forces
-cupula-hair cells are here in semicircular canals
-otolith mass- hair cells are here in utricle and saccule

Question 8

vestibular mechanism

Answer 8

-cupula or otolith mass moves causing movement of hair cells
-kinocilium- determines if hyperpolarization or depolarization
-hair cells move towards it -> depolarization
-hair cells move away -> hyperpolarization -> inhibition

Question 9

semicircular canal mechanism

Answer 9

-counterclockwise endo lymph movement -> left horizontal semicircular canal -> hair cells move towards the kinocilium -> depolarization -> excitation
-only happens when you first rotation head-> endolymph catches up
-when you move counter clockwise the left ampulla is excited and the right ampulla hyperpolarizes (inhibits)
-excites the ear you are moving towards
-connects to eyes so we can move them accordingly to rotational movement

Question 10

utricle and saccule mechanisms

Answer 10

-sitting upright- utricle is horizontal and saccule is vertical
-signal sent to brain so we know where we are going
-stereocilia towards kinocilium -> depolarizes
-signal also sent down for posture -> Reflexes so we dont fall over

Question 11

vestibular pathways

Answer 11

-afferent nerves terminates at vestibular nuclei of the medulla
-several pathways
-medial and superior nuclei receive input from semicircular canal and send to extra-ocular muscles -> move accordingly to rotation
-lateral vestibular nucleus input from utricles -> spinal cord -> posture
-inferior vestibular nuclear input from utricles saccule and semicircular canals -> brain and cerebellum

Question 12

nystagmus

Answer 12

-if we rotate head slowly to left our eyes move to the right-> maintain constant direction of gaze
-once we reach limit of lateral movement -> rapid eye movement in same direction as head rotation
-postrotatory- suddenly stop rotation of head and eyes move opposite of rotation

Question 13

vestibulo-ocular reflexes tests

Answer 13

-Barany test- test vestibular apparatus
-rotating a person and making sure of normal nystagmus
-caloric test- changing temp of semicircular canal -> change properties of endolymph
-warm water- increase liquidity- nystagmus towards treated side
-cold water- decreases liquidity- nystagmus towards untreated side