hearing, balance, taste and olfaction Flashcards
sound
sound is a longitudinal wave
frequency of sound is the number of cycles per second (Hz)
amplitude of sound waves=Db
as air pressure goes up and down it causes movement in the ear drum and that allows us to perceive sound
3 parts of the ear
outer ear (pinna, ear canal and tympanic membrane)
middle ear (ossicles)
inner ear (cochlea and labyrinth)
role of the pinna
capture sound efficiently
sound localisation
ridges and bumps of outer ear reflect sound and focus it into the auditory canal
what is the auditory canal filled with?
air
where does the outer ear stop?
tympanic membrane (ear drum)- vibrates when sound hits
role of the middle ear
transmit mechanical energy captured at the ear drum from sound through the ear to the cochlea
role of the inner ear
mechanical energy - fluid waves - action potential
what are the 3 bones of the ossicles?
malleus, incus and stapes
how do the ossicles and ear drum enable the amplification of sound information?
ossicles are stiff and the ear drum is larger than the oval window where the stapes is means we have an increase in 25 in the energy going from the ear drum to the window
the malleus is attached to the eardrum, and when the eardrum vibrates, it moves the malleus.
the incus is positioned between the malleus and the stapes and acts as a lever, transmitting the vibrations from the malleus to the stapes
the stapes is the last bone in the chain, and it vibrates against the oval window, a membrane-covered opening to the inner ear, transferring the vibrations to the cochlea
direction of the ossicles
tymapnic membrane- malleus- incus- stapes terminates at the oval window
what muscles are by the ossicles?
stapedius and tensor tympani muscles
what is the role of the stapedius and tensor tympani?
stapedius- contracts in response to loud sounds, dampening the vibrations of the stapes, thereby reducing the sound intensity transmitted to the inner ear
tensor tympani- contracts to reduce the movement of the eardrum (tympanic membrane), thereby moderating the sensitivity of the middle ear
what is the middle ear filled with?
air
what is the cochlear composed of (scalae)?
scala vestibululi (starts in the oval window)
scala media
scala tympani (ends in round window)
what is the cochlea filled with?
fluid
what is the organ of corti?
runs the entire length of the cochlea and contains the hair (auditory) receptors along the basilar membrane
pathway of sound
sound causes tympanic membrane to vibrate
these vibrations are passed via the ossicles to the oval window
this causes the stapes to vibrate against the oval window and this generates a fluid wave that travels down the length of the cochlea
oscillatory pressure differences propagate along the scala vestibuli and tympani
what is the hole at the end of the basilar membrane called?
helicotrema
what does the helicotrema allow?
fluid wave to pass through and come down the scala tympani
what happens to left over energy in the ear?
round window bulges out and that absorbs remaining energy so fluid wave can continue
what does a fluid wave do to the basilar membrane?
causes it to move so the hair cells start to move in response to the changing in fluid pressure
what are the two ends of the basilar membrane?
basal (narrow by stapes) and apical (wide)
hair cells on the basal end respond to…
higher frequencies because they are stiff
hair cells on the apical end respons to…
lower frequencies because they are flexible
