Chapter 11: The Auditory and Vestibular System Flashcards
audition
sense of hearing
vestibular system
regulates the sense of balance, posture; head, body, and eye movement.
frequency
the number of compressed patches of air that pass by our ears each second, measured in Hertz. The number of waves per second corresponds to frequency.
pitch
a sound having high or low tone, determined by frequency.
intensity
amplitude, the height of each wave, sound intensity determines the loudness we perceive.
pinna
part of outer ear, the visible portion of the ear consists of cartilage covered by skin that forms this funnel that helps collect sounds from a wide area.
auditory canal
part of the outer ear, the entrance to the internal ear, extends about 2.5 cm inside the skull.
tympanic membrane
part of the middle ear, where auditory canal connects, known as eardrum.
ossicles
part of middle ear, a series of bones connected to the medial surface of tympanic membrane. They transfer movements of the tympanic membrane into movements of a second membrane covering a hole in the bone of the skull.
oval window
part of inner ear, where the ossicle transfers movements of the tympanic membrane into movements in this second membrane.
cochlea
part of inner ear, behind the oval window thats filled with fluid, contains the apparatus for transforming the physical motion of the oval window membrane into a neuronal response.
basic auditory pathway
sound waves move the tympanic membrane -> tympanic membrane moves the ossicles -> ossicles move the membrane at the oval window -> motion at the oval window moves fluid in the cochlea -> movement of fluid in the cochlea causes a response in sensory neurons.
outer ear
the structures of the pinna to the tympanic membrane
middle ear
the tympanic membrane and the ossicles
inner ear
apparatus medial to the oval window
nuclei in the brain stem
once a neural response to sound is generated in the inner ear, the signal is transferred to and processes by this nuclei.
medial geniculate nucleus
output from nuclei in the brain stem is sent to this in the thalamus.
primary auditory cortex
the MGN projects to this located in the temporal lobe.
Eustachian tube
allows the air in the middle ear to be continuous with the air in the nasal cavities.
footplates of stapes
sound force amplification by the ossicles
attenuation reflex
response when onset of loud sound causes tensor tympani and stapedius muscle contraction, adapts ear to loud sounds, protects inner ear, enables us to understand speech better.
anatomy of cochlea
three fluid-filled tunnels - scala vestibuli, scala media, and scala tympani. Also has oval window and round window
Basilar membrane
separates the scala tympani from the scala media.
Reissner’s membrane
separates the scala vestibuli from the scala media
Tectorial membrane
hangs over organ of Corti
Organ of Corti
contains auditory receptor neurons
hair cells
the auditory receptors that lie between the basilar membrane and the tectorial membrane in the cochlea
helicotrema
at the apex of the cochlea, the scala media is closed off, and the scala tympani becomes continuous with the scala vestibula at this hole in the membranes.
perilymph
fluid in scala vestibuli and scala tympani, low potassium and high sodium concentrations.
endolymph
fluid in scala media, high potassium and low sodium concentrations
endocochlear potential
endolymph electrical potential 80 mV more positive than perilymph
stria vascularis
the difference in ion content is generated by active transport processes taking place here.
Physiology of the cochlea
motion at oval window pushes perilymph into scala vestibuli, makes round window membrane bulge.
response of the basilar membrane to sound
two structural components of basilar membrane - wider at apex, stiffness decreases from base to apex. Endolymph movement bends basilar membrane near base, wave moves toward apex.
place code
the response of the basilar membrane establish this in which different locations of membrane are maximally deformed at different sound frequencies.
place code theory
each area along the basilar membrane has hair cells sensitive to only one specific frequency of sound wave. Each frequency activates the hair cells at only one place along the basilar membrane, the nervous system distinguishes among frequencies based on which neurons respond.
tonopoy
systematic organization of sound frequency within an auditory structure, analogous to retinotopy in the visual system.
stereocilia
hair looking extensions from hair cells.
transduction
transducing sound into a neural signal is the bending of these cilia.
reticular lamina
this is in the middle of the basilar membrane and tectorial membrane, holding onto the hair cells.
inner hair cells
hair cells between the modiolus and the rods of Corti
outer hair cells
cells farther out than the rods of Corti
spiral ganglion
hair cells form synapses on neurons whose cell bodies are located here
auditory vestibular nerve
axons from the spiral ganglion enter the auditory nerve, a branch of this nerve projects to the cochlear nuclei in the medulla.
transduction by hair cells
ion channels on stereocilia tips are opened when the tip links joining the stereocilia are stretched, the entry of potassium depolarizes the hair cell which opens a voltage-gated calcium gated channel, incoming calcium leads to the release of glutamate that diffuses to the postsynaptic nuerite from the spiral ganglion.
tip link
displacement of the cilia in one direction increases tension on this, increasing inward potassium current. The entry of potassium into hair cell causes depolarization that activates calcium channels, releasing glutamate that activates the spiral ganglion.
auditory nerve fiber
afferents from the spiral ganglion enter the brain stem here
dorsal/ventral cochlear nucleus
at the level of the medulla, the axons innervate the dorsal and ventral cochlear nucleus ipsilateral to the cochlea where the axons originated.
superior olive
cells in the ventral cochlear nucleus send axons that project to this on both sides of the brain stem
inferior colliculus
axons of the olivary neurons ascend in the lateral lemniscus and innervate this of the midbrain.
medial geniculate nucleus
the neurons in the inferior colliculus send axons here in the thalamus, which in turn projects to auditory cortex.
acoustic radiation
axons leaving MGN project to auditory cortex via internal capsule in array
Area A1
important for auditory imagery, damage doesn’t produce deafness, cells here mainly respond to tones of a particular frequency
damage to primary auditory cortex
have trouble with speech and music, but they identify and localize single sounds well.
primary auditory cortex
the destination for most information from the auditory system, located in the superior temporal cortex.
tonotopic organization
the auditory nerve and auditory cortex have this, neurons responding to higher frequencies are located on the periphery and those responding to lower frequencies more centrally.
time of arrival
method to determine the direction and distance of a sound to compare the responses of the two ears.
difference of intensity
cue for location of sound between ears
sound shafow
making the sound louder for the closer ear.
amusia
tone deafness, impaired detection of frequency changes, have trouble recognizing tunes.
absolute pitch
perfect pitch, ability to hear and identify a note, genetic predisposition contributes.
conductive/middle ear deafness
hearing loss that occurs if the bones of the middle ear fail to transmit sound waves properly to the cochlea. Can be caused by disease, infections.
nerve/inner ear deafness
hearing loss that results from damage to the cochlea, the hair cells, or the auditory nerve, can vary in degree, can be confined to one part of the cochlea.
tinnitus
frequent or constant ringing in the ears, experienced by many people with nerve deafness.
vestibular labyrinth
Otolith organs - gravy and tilt
Semicircular canals - head rotation
Use hair cells, like auditory system, to detect changes.
vestibular sense
system that detects the position and movement of the head, directs compensatory movements of the eye and helps maintain balance, senses the direction of tilt and the amount of acceleration of the head.
saccule and utricle
large chambers near the center of the labyrinth
Scarpa’s ganglion
where 20,000 vestibular nerve axons on each side fo the head cell bodies lie
Otolith organs
the saccule and utricle detect changes of head angle, as well as linear acceleration of the head
linear acceleration
forces due to this are the sort you encounter when you ride in an elevator or a car as it starts or stops.
uticular macula
when this is level, the cilia from the hair cells also stand straight
otoconia
pulled when the head and macula are tilted, this deforms the gelatinous cap, and the cilia bend.
semicircle canals
detect turning movements of the head, such as shaking your head from side to side or nodding up and down. Also sense acceleration. first the cilia of hair cells penetrate the gelatinous capula, which is bathed in the endolymph that fills the canal. When the canal rotates leftward, the endolymph lags and it applies force to the capula, bending the cilia within it.
angular acceleration
generated by sudden rotational movements, and it is the primary stimulus for the semicircular canals.
