lect 9- Auditory Senses Flashcards
describe the conduction pathway sequence (auditory)
tympanic membrane –> malleus –> incus –> stapes –> oval window
what does the malleus articulate with
the anvil (incus)
what does the malleus attach to
tympanic membrane
describe the incus (anvil)
intermediate bone between the stapes and the malleus; the name “incus” refers to an anvil, on which the hammer (malleus) strikes
what is the third bone in the series in the middle ear
stapes
what does the stapes insert onto
oval window
what does the oval window open into
scala vestibuli
where is the round window located
at the end of the scala tympani
what does the tensor tympani do
inserts on the malleus and pulls handle of malleus inward
what does the stapedius muscle do
inserts on the stapes and pulls stapes outward
when do the muscles of the middle ear contract
contract reflexively in response to loud sounds in order to dampen the vibrations of the auditory ossicles
what provides the impedance matching between the air and the fluid
the tympanic membrane and auditory ossicles
what are the major components of the cochlea
scala vestibuli, scala media, scala tympani and reissner’s membrane
what separates scala medial from scala vestibuli
Reissner’s membrane (vestibular membrane)
what does the basilar membrane separate
separates scala media from scala tympani
describe the basilar fibers
length increases from the oval window to the apex of the cochlea (helicotrema) and diameter of the fibers decrease from oval wind to the apex of the cochlea
what is the result of the different tights of fiber distribution in basilar fibers
still, short fibers near the oval window beat at a high frequency; long, limber fibers near the apex of the cochlea vibrate at a low frequency
what does the organ of corgi generate nerve impulses in response to
vibration of basilar membrane
what type of cells are the sensory receptors of the organ of corti
hair cells
what creates the rigid unit of the organ of corti
outer ends of hair cells are tightly attached to reticular lamina, supported by rods of corgi, which are attached to the basilar fibers.
what cranial nerve is involved with the organ of corti
CN 8: cochlear nerve
what does movement of the basilar fibers cause movement in
reticular lamina
what happens to hair cells when the basilar membrane moves
hair cells become excited
what is the scala media filled with
endolymph
what is the scala vestibule filled with
perilymph
what is the scala tympani filled with
perilymph
describe the concentrations of potassium and sodium in the endolymph
high concentrations of potassium and low concentration of sodium (perilymph is the opposite)
what is the different in mV between endolymph and perilymph and what is this called
called the endocochlear potential and is +80mV
what is the intracellular potentials of hair cells with respect to perilymph and endolymph
perilymph: -70mV
endolymph: -150 mV
define place principle
nervous system detects frequencies by determining positions along the basilar membrane that are most stimulated
list the components of the nervous system pathway (in order):
spiral organ of corgi, dorsal and ventral cochlea nuclei, superior olivary nucleus, lateral lamniscus nucleus, medial geniculate nucleus (thalamus), auditory cortex
