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Function of the pharyngotympanic tube
Equalizes pressure in the middle ear cavity with the external air pressure
Function of the small bones in the tympanic cavity
Transmits vibratory motion of the tympanic membrane to the OVAL window dampened by the tensor tympani and stapedius muscles.
part of the inner ear. Tortuous channels worming their way through the temporal bone. Contains the vestibule, the cochlea and the semicircular canals.
The "floor" of the cochlear duct is composed of
the bony spiral lamina and the basilar membrane which supports the organ of corti
How the tympanic membrane works
Pushes the ossicles, which presses fluids in the inner ear against the oval and round windows
The movement of what sets up shearing forces that pull on mechanosensitive hair cells
Transmission of sound to the inner ear needs
stimulation of the organ of corti and generation of impulses in the cochlear nerve
The audible sound waves excites specific hair cells according to what
According to the FREQUENCY of sound
during the bending of stereocilia, when it opens MECHANICALLY GATED ion channels found where the stereocilia meet the hair cell.
Bending stereocilia causes
causes a graded potential and the release of a neurotransmitter: termed Mechanotransduction
The neurotransmitter released by mechanotransduction causes
cochlear fibers to transmit impulses to the brain, where sound is perceived
Impulses from the cochlear nuclei are sent
to the superior olivary nucleus.
Inferior colliculus (auditory reflex center)
4 types of deafness
1) conduction deafness
2) Sensorineural deafness
4) Meniere's syndrome
something hampers sound conduction to the fluids of the inner ear (e.g., impacted earwax, perforated eardrum, osteosclerosis of the ossicles)
More common. Results from damage to the neural structures at any point from the cochlear hair cells to the auditory cortical cells
Labyrinth disorder that affects the cochlea and the semicircular canals, causing vertigo, nausea and vomiting. Also Progressive hearing loss.
Otolithic movement in the direction of kinocilia:
depolarizes vestibular nerve fibers
increases the number of action potentials generated
Otolithic movement in the opposite direction:
Hyperpolarizes vestibular nerve fibers
Reduces the rate of impulse propagation
Stereocilia move TOWARDS the kinocilium and what happens
and the signal increases in frequency (depolarization) compared to the normal tonic level
Stereocilia move AWAY from the kinocilium and what happens
and the signal decreases in frequency (hyperpolarization) compared to the normal tonic level.
Each crista contains what
Has support cells and hair cells that extend into a gel-like mass called the cupula
Directional bending of hair cells in the cristae causes:
1) depolarizations, and rapid impulses reach the brain at a faster rate
2) Hyperpolarizations and fewer impulses reach the brain.
What is the result of the directional bending of hair cells in the cristae
result is that the brain is informed of rotational movements of the head
Depolarization occurs in the SAME direction as the head movement. (Left head turn produces depolarization in the LEFT horizontal canal)
Anterior and Posterior Canals
Depolarization occurs in the OPPOSITE direction as the head movement (FORWARD head tilt produces depolarization of the POSTERIOR canals)
Ordinarily the head movement implied by the visual and vestibular signals are equal but there can be conflict resulting in a) motion sickness b) vertigo
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