Physiology of the auditory system Flashcards
What is intensity in a sound wave determined by?
amplitude
What is pitch in a sound wave determined by?
frequency
What is timbre?
qulity of the sound
What is impedence matching?
high impedence of fluid in the cochlea so middle ear bones overcome the loss of sound by increasing the sound pressure
What are the three mechanisms for impedence matching?
area ratio of the ear drum to the stapes footplate; lever action of the ossicles-arm of malleus is longer than incus; buckling of the ear drum
What is foudn in the floor of the scala media?
basilar membrane which contains the organ of corti
What is found in the ceiling of the scala media?
reissners membrane
What two areas are separated by reissners membrane?
scala vestibuli and scala media
What 2 areas are separated by the basilar membrane?
scala media and scala tympani
What area is connected to the round window?
scala tympani
Where do the scala tympani and scala vestibuli connect?
helicotrema
What determines the distance a particular frequency travels?
the width and flexibility of the basilar membrane
How does the basilar membrane change as you go through the cochlea?
gets thinner and wider
Where do low frequencies vibrate the basilar membrane?
near the apex- thinner
Where are the cilia of the organ of corti embedded?
in the tectorial membrane
Where do the cells of the organ of corti sit?
on the basilar membrane
Where does the organ of corti synapse?
the spiral ganglion
What does force towards kinocilium cause?
opens TRPA1 channel letting K into cell, depolarising
What is the function of outer hair cells?
control stiffness, amplify membrane vibration- efferent input
What protein in the membrane of outer haircells can change the length of the cell?
prestin
What is the response of a outer hair cell to sound?
receptor potenetial and a change in length
Why does K travel into the cell in contrast to in otehr parts of the body?
there is a higher K conc. than normal in endolymph so conc. grad inwards
What are the 2 mechanisms for frequency coding?
place code ( where on the basilar membrane vibrates); temporal code
What is temporal coding in the auditory nerve?
APs are generated at the same frequency as the sound wave
How can APs be generated at the same frequncy as sound wave if there is a limit on the number of APs per minute?
summation- all neurons innervating a sinle hair cell code freuqncy together
What is the auditory system pathway?
cochlea–cochlear nucleus in medulla–superior olivary nucleus–inferior colliculus–medial geniculate body–audotory cortex
What are the 3 different cochlear nuclei in the medulla?
dorsal cochlear nucleus; posteroventral cochlear nucleus; anteroventral cochlear nucleus
What is the function of the superior olivary nucleus in the auditory pathway?
locate sound sources in space
What is the function of the medial superior olive?
computes sound arrival at the two ears–ipsilateral ear earlier than contraltaeral
What part of the vestibular system is responsible for head angular acceleration?
semicircular canals
What part of the vestibular system is responsible for head linear acceleration?
saccule and utricle
What deforms the hair cells in the labyrinth?
acceleration/gravity
What direction of the stereocilia causes depolarisation?
towards the kinocilium
What is the crista?
sheet of cells where hair cells are clustered
Where do the cilia project into?
cupula
What plane is the saccule concerned with?
vertical plane
what plane of movement is the utricle concerned with?
horixontal plane
Where do the hair cells lie in the otolith organs?
macula
What divides the hair cells in the otolith organs?
striola
What is the orientation of the hair cell cilia in the otolith organs?
in all directions
What are otoconia?
crystals of calcium carbonate that lie on the otolithic membrane-gravity
What is the function of the striola of the macula?
allows otolith organs to have multidirectional sensitivity
What is the signal of the macular affferents?
tonic, deviations from which are sensitive to acceleration
What are the 3 main vestibular reflexes?
vestibulo-ocular reflex; vestibulo-colic reflex and the vestibular-spinal reflex
What is the function of the vestibulo-ocular reflex?
keep the eyes still in space when the head moves
What is the function of the vestibulo-colic reflex?
keeps the head on a level plane when you walk
What is the function of the vestibul-spinal reflex?
adjusts posture for rapid changes in position
