PHYS: Auditory + Vestibular Flashcards
What is sound?
Oscillations of air pressure that vary rapidly w/ time
What has a lot of potassium in it?
Endolymph
At which ends of cohclear hair cells do endolymph + perilymph bathe in?
Endolymph = apical end (high in K+) – ICF
Perilymph = basal end (low in K+) – ECF
Where are endolymph + perilymph found?
endolymph = scala media
perilymph = scala vestibuli + scala tympani
With high frequences, where along the basilar membrane does it move the most?
The base
The Organ of Corti contains hair cells, which act as __________ to convert mechanical signals to electrical signals.
Mechanoreceptors
*hair cells = NOT NEURONAL
Which side of a hair cell has stereocilia?
Apical
*neuronal synapse = basal side
When the hair cells are deflected from vibrations, what enters the cell to depolarize it?
K+ through TRPA1 ion channel
This creates a large electrochemical gradient w/ large endolymphatic potential
Once, the hair cell is depolarized what happens?
Voltage-gated Ca+ channels open, incomming calcium leads to the relase of excitatory glutamate neurotransmitter, which generates an action potential in CN 8 spiral gangalion.
Since all the stereocilia are linked together, if there is deflection toward the tall stereocilia what happens?
Excitation
*deflection towards short = inhibition (hyperpolarization)
What is the function of the stria vascularis?
Maintains electrochemical properties of endolymph
What is the function of the one row of inner hair cells?
Auditory Information (main source)
What is the function of the 3 rows of outer hair cells?
Act as an amplifier
Contractile
Boost vibrations of basilar membrane
Where are hair cells located?
On basilar membrane
What do the hair cells recieve afferent + efferent innervation from?
Afferent = spiral ganglia
efferent = superior olivary complex
Describe the innervation of inner hair cells?
Type 1 afferents
Describe the innervation of outer hair cells?
BOTH
Type 2 afferents
+
efferents
Memorize how sound is transmitted
The cochlear nuclear complex has a dorsal + ventral nuclei, what are their functions?
dorsal cochlear nuclei (DCN) = localizes sound (blends sound w/ somatosensory)
ventral cochlear nuclei (VCN) = nature of the sound (high, low)
What is the first site in the brainstem where information from both ears converge?
Superior olivary complex
The superior olivary complex is important in:
Localizing sound
Which superior olivary complex generates a map of the interaural TIME differences of sound arrival to ears (to localize sound)?
MSO
(medial = main)
*they see which ear has sound that gets to MSO first, that way you know which direction it came from
What does the LSO do?
Generates a map of the interaural INTENSITY differences
What is the function of the inferior colliculus?
It suppresses echoes –> which would interfere with sound localization
Makes a spatial map of sound
What does the superior colliculus do?
Takes the location data from the IC and adds vertical height –> which creates a spatial map of the sounds location
*SC + IC work together
What is the medial geniculate nucleus used for in the sound pathway?
It is literally just a relay station
What is essential for conscious perception of sound (beginning to interpret a sound)?
Primary auditory cortex (A1)
What 3 things comprise the efferent input to the auditory system?
- Olivocochlear efferents
- Middle ear muscle motor neurons
- Autonomic innervation of the inner ear
What does the auditory (secondary) association cortex (A2) do?
This has Brocas + Wernickes
It responds to more complex sounds (music) + naming a sound + speech
What efferent protects hair cells from damage to intense sounds?
Olivocochlear efferents
They reduce the response to noise
The middle ear efferents connect to the tiny muscles in the ear (tensor tympani) + (stapes) and contract them to decrease the transmission of sound. Therefore, their function is to:
Prevent ear damage
What are otoacoustic emissions?
Make the ear emit sound!
Tested in a newborn hearing screen
What is sensorineural hearing loss?
Damage to hair cells/nerve fibers
Might be restored w/ a cochlear prosthesis
What stimulates angular acceleration?
Motion w/ rotation
Spinning + turning
Falling forward/backward
What stimulates linear acceleration?
Motion in a horizontal or vertical plane:
- moving along a line
- jumping
- walking
What activates semicurcular canals?
Rotational acceleration
What activates the utricle?
Linear acceleration (forward/backward)
What activates the saccule?
Linear acceleration up/down
*sac a hoop
What best detects rotation in the horizontal plane?
Horizontal semicircular canal
Falling backwards is best detected by?
Posterior semicircular canal
Falling forwards is best detected by:
Anterior semicircular canal
If we are falling what reflex kicks in?
A reflex that is designed to keep our eyes on the horizon.
If you are spinning which muscle is activated?
Medial rectus
(lateral = inhibited)
If you are falling backwards which muscle is activated/inhibited?
superior oblique = activated
inf. oblique = inhibited
*eyes move down to stay on horizon
When you fall forward which muscles are activated/inhibited?
Sup. rectus = activated (look up towards horizon)
Inf. rectus = inhibited
What fluid is found within the vestibular apparatus?
Endolymph
(the fluids work inside semicircular canals as pressure gradients)
