The Auditory and Vestibular System Flashcards
Outer ear
collects sound waves and channels them into the ear canal,where the sound is amplified
Inner ear
Sense and process information about sound and balance, and send that information to the brain
Middle ear
Transmits sound from the outer ear to the inner ear
Bones of the middle ear
malleus, incus, stapes
Tympanic Membrane
Separates the outer ear from middle ear
What happens when sound waves reach the tympanic membrane? (3)
- They cause the membrane to vibrate.
- The vibrations are then transferred to the tiny bones in the middle ear.
- The middle ear bones then transfer the vibrating signals to the inner ear
What regions are located at the basal end of the cochlea?
oval window, round window
Oval Window
Connects the middle ear and inner ear, through which sound vibrations from stapes are transmitted.
Round Window
Allowing the movement of ear fluid within the cochlea, which results in the movement of the inner hair cells of the cochlea
What three fluid-filled channels are located within the cochlea
scala vestibuli, scala media, scala tympani
Which tube(s) in the cochlea is/are filled with perilymph?
scala vestibuli, scala tympani
Which tube(s) in the cochlea is/are filled with endolymph?
scala media
Difference between basilar and tectorial membrane
Basilar= Auditory receptor cells, called hair cells, lie embedded within the basilar membrane.
Tectorial membrane: Lies over the hair cells; it serves as a shelf against which the cilia of hair cells brush upon movement.
Organ of Corti
An organ of the inner ear located within the cochlea which produces nerve impulses in response to sound vibrations.
The organ of Corti (black) sits on a thin, flexible membrane called the ______ membrane (red) and under a relatively immobile membrane called the ______ membrane (blue).
basilar; tectorial
Stereocilia location
In the organ of corti and are embedded in the tectorial membrane
Function of stereocillia
Transform the mechanical energy of sound waves into electrical signals for the hair cells, which ultimately leads to an excitation of the auditory nerve.
The base of the basilar membrane (near oval window) is “tuned” for (LOW / HIGH) frequencies. This region of the membrane is (WIDER / NARROWER) and (LESS / MORE) flexible.
high; narrow and less
The apex of the basilar membrane (near helicotrema) is “tuned” for (LOW / HIGH) frequencies. This region of the membrane is (WIDER / NARROWER) and (LESS / MORE) flexible.
low; wider and more
Relationship between frequency and wavelength
The higher the frequency, the shorter the wavelengths and therefore the distance of travel is lower
Vertical movement of the basilar membrane is translated into?
Tectorial membrane moving across the tops of the hair cells, creating a shearing force that bends the sterocillia of the hair cells
Bending the stereocilia toward the kinocilium (upward phase) causes ______ and bending it away from the kinocilium (downward phase) causes __________
depolarization; hyperpolarization
mechanoelectrical transduction.
mechanisms by which cells convert mechanical stimulus into electrochemical activity.
What happens when the hair bundle is deflected toward the tallest stereocilium?
1) Cation-selective channels open near the tips of the stereocilia, allowing K+ to flow into the hair cell.
2)The resulting depolarization opens voltage-gated Ca+ channels in the cell soma, allowing the release of neurotransmitter onto the the nerve endings of the auditory nerve.
What fluid of the inner ear is K⁺-rich and Na⁺-poor?
Endolymph (The stereocilia of the hair cells protrude into the endolymph)
What fluid of the inner ear is K⁺-poor and Na⁺-rich?
Perilymph
What does the endocochlear potential drive?
K+ into open transduction channels located at the apical ends of the stereocilia; the resulting depolarization of the hair cell body opens somatic K+ channels.
The negative resting potential of the hair cell and the low K+ concentration in the surrounding perilymph result in?
An outward K+ current through these somatic channel
Tuning Curve
The frequency sensitivity of a hair cell can be displayed as a tuning curve
Steps of Auditory Pathway
1) Signals travel along the cochlear nerve to cochlear nuclei on the same side of the body -rostral medulla
2)The superior olivary (midbrain) nucleus takes the information from the cochlear nucleus and begins the process of interpreting and combing information.
3) After the superior olivary nucleus, auditory processing continues on to a nucleus lateral nucleus lemniscus and then the called the inferior colliculus (IC)
4) The medial geniculate nucleus of the thalamus then receives the auditory information from the three brainstem nuclei
5) The information is integrated and the medial geniculate nucleus projects that information to the auditory cortex in the temporal lobe of the cerebral cortex.
Medial Superior Olive
contains the neural circuity to compute interaural time differences?
Lateral Superior Olive
contains the neural circuity to compute interaural intensity differences?
MSO Neurons Respond to
Respond to differences in the time that a given stimulus reaches each of the ears,
LSO Neurons Respond to
Respond to slight differences in the amplitude of sound waves reaching each ear
Interneural time Difference
The difference in arrival time of a sound between two ears.
LSO receives excitatory input from the __________ and inhibitory input from the ________
ipsilateral ear ; contralateral ear
MSO recieve __________ inputs from the right and left ______
bilateral ; AVCNs.
Location of lateral nucleus leminucus and IC (Inferior colliculus) and (medial geniculate complex of the thalamus)
pons-midbrain junction; caudal midbrain ; rostral midbrain
Secondary auditory cortex
important role in sound localisation and analysis of complex sounds, auditory memory
Main Structures of Vestibular System
2 otolith organs [utricle and saccule] + 3 semicircular canals)
Functions of otolith organs
Utricle: Linear accelerations and head-tilts in the horizontal plane
Saccule: detects the linear acceleration in the vertical plane.
What part of the vestibular labyrinth detects rotational acceleration?
semicircular canals
Steps of Electrical Resonance
1)By creating a force in one or the other direction, these sterocillia are displaced, K+ channels open and there is an influx in potassium, leading to depolarization, opening up voltage gated calcium channels and there is an influx of calcium
2) Ca2+ activates K+ channel and k+ exits the cell, repolarizing cell
3)The interplay between what two ion channels results in the electrical resonance
Electrical Resonance
A description of small membrane potentials in membrane which are creating an oscillatory pattern
Overlying the vestibular hair cells and their hair bundles is a(n) ______ ______ (1); above this layer is a fibrous structure, the ______ ______ (2), in which are embedded crystals of calcium carbonate called _______ (3).
gelatinous layer, otolithic membrane, otoconia
What do both the utricle and saccule contain? What does it consist of?
Contain a sensory epithelium, called the ,macula which consists of hair cells and associated supporting cells.
In the saccular macula, are the kinocilia directed toward or away from the striola? Horizontally or vertically?
away from, vertically
In the utricular macula, are the kinocilia directed toward or away from the striola? Horizontally or vertically?
toward: horzintoally
Relationship between firing rate and head tilt? Head upright vs when it tilts?
head upright: Vestibular nerve fibers have a steady and relatively high firing rate
Tilted: Increases or decreases depending on direction of tilt
Cupula
-Gelatinous mass found in the ampulla, providing the sense of spatial orientation
function of cristae ampullaris and location
Location: present in the ampullae of the semicircular canals
Function: sense angular acceleration and deceleration.
Cupula Function
Ensures the perilymph and endolymph remain separate
The thalamocortical pathways carry vestibular information to the vestibular cortex which consists of two cortical targets: the posterior ______ cortex for motor function and the region near the representation of the face in the _____________
parietal, primary somatosensory cortex
Pathway of Vestibular Information
1) The lateral and superior vestibular nuclei
(pons) send axons to the ventral posterior nucleus (VPN) complex of the thalamus.
2) This, in turn, projects to two cortical areas relevant to the perceptions arising from the processing of vestibular information.
3) One of these cortical targets is just posterior to the primary somatosensory cortex, near the representation of the face; the other is at the transition between the somatic sensory cortex and the motor cortex.
vestibulo-ocular reflex (VOR)
to stabilize gaze during head movement, with eye movement due to activation of the vestibular system
Descending projections from the vestibular nuclei are essential for postural adjustments of the head, mediated by the ______ and body, mediated by the ______
vestibulo-cervical reflex (VCR), vestibulo-spinal reflex (VSR)
Vestibulosympatic Reflex (VSR)
Stabilize the body
VCR
Attempts to stabilize head position in space during motion of the body by generating generating a command to move the head in the direction opposite to that of the current head-in-space motion
Oculumotor Nucleus Location & Function
Location: Midbrain
Function: Control eye movements
Function of bones in the middle ear
transmit vibrations from the ear drum farther into the inner ear
