auditory Flashcards
sound
audible variations in air pressure
sound frequency
number of cycles per second expressed in units called hertz (Hz)
cycle
distance between successive compressed patches
human sound range
20-20,000 Hz
high pitch =
high frequency
which is louder, higher or lower intensity?
HIGHER
stages of auditory pathway (in order)
- sound waves
- tympanic membrane
- ossicles
- oval window
- cochlear fluid
- sensory neuron response
auditory pathway
- auditory receptors in cochlea
- brain stem neurons
- MGN in thalamus
- auditory cortex (A1)
pressure is forced by
surface area
how does fluid move?
when pressure at oval window is GREATER than tympanic membrane
attenuation reflex
response where onset of loud sound causes tensor tympani and stapedius muscle contraction
function of attenuation reflux
adapt ear to loud sounds, understand speech better
perilymph
fluid in scala vestibuli and scala tympani
endolymph
fluid in scala media
endocohlear potential
endoplymph electric potential 80 mV MORE positive than perilymph
physiology of cochlea
pressure at oval window pushes perilymph into scala vestibule, round window membrane bulges out
structural properties of basilar membrane to sound
winder at apex, stiffness decreases from base to apex
Georg von Bekesy research
endolymph movement bends basilar membrane near base, wave moves TOWARDS apex
A.J Hundspeth research
basilar membrane upward, reticular lamina up and stereo cilia bends outward
function of outer hair cells
sound transduction
motor proteins
change length of outer hair cells
prestin
required for outer hair cell movement
characteristic frequency
frequency at which neurons is most responsive - from cochlea to cortex
what type of neurons are present in the superior olive?
biaural neurons
biaural neurons
receive information from both ears
encoding information about sound intensity
- firing rate of neurons
- number of active neurons
low frequencies
phase-locking on every cycle or some fraction of cycles
high frequencies
NOT fixed
interaural time delay
time taken for sound to reach from ear to ear (20-20,00 Hz)
interaural intensity difference
sound at high frequency from one side of ear (2,000-20,000 Hz)
mechanism of sound localization
- sound from left: activity in left cochlear nucleus sent to superior olive
- sound reaches right ear, activity in right cochlear nucleus, first impulse far
- impulses reach olivary neuron at the same time = summation = action potential;
vertical sound localization
based on reflections from the pinnae
primary auditory cortex
axons leaving MGN project to auditory cortex via internal capsule in array
tonotopy
columnar organization of cells with similar binaural interaction
lesion in auditory cortex
normal auditory function
lesion in striate cortex
complete blindness in one visual hemifield
different frequency band information
parallel procession, localization deficit
frequency tuning
similar to characteristic frequency
isofrequency bands
similar characteristic frequency, diversity among cells
importance of vestibular system
balance, equilibrium, posture, head, body, and eye movement
otolith organs
- gravity and tilt
- detect changes in head angle and linear acceleration
semicircular canals
head rotation
hair cells
used like auditory system to detect changes
what cells respond to tilt?
macular hair cells
push-pull activation of semicircular canals
- 3 on 1 side
- help sense all possible head-rotation angles
- each paired with another on opposite side of head
vestibulo-ocular reflex (VOR)
- line of sight fixed on visual target
- senses rotations of head, commands compensatory movement of eyes in opposite directions
auditory system
senses external movements
vestibular system
senses movements of itself
