Special Senses Hearing Flashcards
what is sound
cyclical compression and rarefaction of air molecules causing a cyclical change in air pressure
what does the pinna do?
shapes, funnels, and conducts sound toward the meatus and tympanic membrane
what is the dual function that pinna has in many species?
hearing and thermoregulation
what part of the ear is an air-filled cavity?
middle ear
what part of the ear is the fluid-filled cavity?
inner ear
what does the choclear duct contain?
endolymph
what houses the hair cells that are anchored to the basilar papilla?
organ of corti
what is the gel-coated ridge that lies on top of the hair cells?
tectorial membrane
what do hair cell synapse onto?
sensory nerves
cochlear nerve -> CN8
what happens to sound waves and different frequencies along the basilar papilla?
resonate at different points -> spatial coding along length of membrane -> tonotopic organization
how is the organ of corti structured longitudinally?
basilar papilla increases in size and flexibility
how is the organ of corti structures in its cross-section?
membranes different in flexibility
how is sound energy in air transmitted to vibrations in tissue?
sound waves hit tympanic membrane -> vibrations transferred to oval window -> oval window deformation -> pressure waves in perilymph of cochlea -> pressure waves travels up basilar membrane
how many layers of sterocilia does each hair cell have?
3
what connects sterocilia?
tip links composed of cell adhesion molecules
In what form is mechanical energy transduced to electrical energy?
action potentials
map out hairs opening -> signaling cochlear nerve
bent hairs open gated cation channels -> K+ enters hair cell -> hair cell depolarizes -> voltage-gated Ca2+ channels open -> neurotransmitters (glutamate) released -> signaling terminals of cochlear nerve
what happens to sensory neurons on hair cells at rest?
transmit AP spontaneously at a specific rate
how are quiet noises detected?
1.pinna - funnels and conducts sounds into ear canal
2. meatus - transmits sound
3. middle ear ossicles - transmit and amplify sound 2-3 times
4. cochlear amplifer
what do outer hair cells do to amplify quiet noises?
change length in response to movements of basilar membrane -> amplification of signal
what is the function of outer hair cells?
increase sensitivity of inner hair cells
where does information originating in one cochlea reach?
both sides
where does information from one cochlea travel?
predominantly up the contralateral side
what does the superior olivary complex do?
sound localization
what does the medial geniculate nucleus & inferior colliculus do?
specialized to detect certain frequency combinations and timing among sounds
what does the auditory cortex do?
conscious perception of sound
Map the auditory NS system
CN8 -> cochlear nuclei -> superior olivary complex -> inferior colliculus -> medial geniculate nucleus -> auditory cortex
what can cause phase delay between ipsilateral and contralateral ear?
time difference and intensity differences
what receives input from both cochlear nuclei?
superior olivary complex
what is the term for louder in one ear?
interaurel intensity difference
what is the term for sound reaching one ear first?
interaural timing differences
what do lateral superior olive cells measure?
interaural intensity differences by integrating ipsilateral excitatory and contralateral inhibitory inputs
what do medial superior olive cells measure?
interaurel time differences using excitatory inputs from both sides
which olive cells measure using excitatory and inhibitory inputs?
lateral superior olive
which olive cells measure using only excitatory inputs?
medial superior
map the auditory pathway with sounds at different frequencies
detect sounds at different frequencies -> bipolar neurons that connect hair cells to cochlear nuclei -> acoustic filtering -> pathway splits to right/left olive -> directionality and sound localization -> tonotopic organization; information routed to vestibulo-ocular reflex and startle response -> awarness of a sound relay to auditory cortex -> conscious localization and perception of sound
what is BAER testing?
brainstem auditory evoked response
how and where can auditory evoked potentials be detected?
detected at surface of skin in response to clicks or certain tones from a speaker
what is required to boost the signal and remove noise in the BAER test?
differential amplification
what calculates the mean value of the clicks to reveal the pattern in a BAER test?
signal averger
what does wave I-VII reflect?
I - cochlea, spiral gangli, CN8
II - cochlear nuclei
III - superior olivary complex
IV & V - lateral lemniscus & lemniscal nuceli, and causal colliculus
VI - medial geniculate body
VII - auditory radiations
which ear can each puppy hear in?
1 - both ears
2 - right ear
3 - left ear
4 - neither ear
what is acquired deafness
hearing loss due to an infection, injury, gradual or sudden hearing loss due to age, noise exposure, drugs
what do ototoxic drugs do?
kill hair cells -> hearing loss
what do aminoglycosides first target and then spread to?
first - hair cells in basal portion of cochlear spiral
spread - outer spiral then nerve
what sounds do aminoglycosides have the most affect on?
high frequency
what coat color is linked to deafness in dog, cat, horse, cow, pig, sheep, ferret, mink, camelid, and rabbit?
white
when does deafness develop due to the loss of melanocyte-dependent blood supply to cochlea?
3-4 weeks
what does binaurel hearing do?
allow for comparing signal from both ears to determine location of a sound in space
where is the binaurel input recieved from both cochlea?
olivary complex
what protects the ear from excessive noise?
two skeletal muscles attached to malleus and stapes
