Exam 7 - Ear Flashcards
(132 cards)
1
Q
The ear is divided into three main regions:
A
External ear, which collects sound waves and funnels them inward
Middle ear, which conveys sound vibrations to the oval window
Internal (inner) ear, which contains the receptors for hearing and for equilibrium
2
Q
which collects sound waves and funnels them inward
A
External ear
3
Q
which conveys sound vibrations to the oval window
A
Middle ear
4
Q
which contains the receptors for hearing and for equilibrium
A
Internal (inner) ear
5
Q
The external ear consists of the
A
Auricle
External auditory canal
Eardrum
6
Q
The rim of the auricle is the
A
helix
7
Q
The inferior portion is the
A
lobule
8
Q
________ lies in the temporal bone, and leads to the eardrum
A
The external auditory canal
9
Q
The eardrum has a covering of
A
epidermis
10
Q
___ ____ are specialized sebaceous (oil) glands that secrete earwax (cerumen), which in combination with hairs that are present helps prevent dust and foreign objects from entering the ear
A
Ceruminous glands
11
Q
The ___ is a small pointed eminence projecting backward over the meatus
A
tragus
12
Q
The ____ is opposite the tragus
A
antitragus
13
Q
Regionally are the mastoid process posterior to the lobule, and the __ __ __ anterior to the tragus
A
superficial temporal artery
14
Q
The middle ear is a small air-filled cavity in the…
A
…temporal bone
15
Q
The middle ear
It is separated from the external ear by the eardrum, and from…
A
the inner ear by the oval window and the round window
16
Q
WHERE IS THE SITE OF TRANSDUCTION FROM LECTURE 1 ????
A
HE said it was important in lecture so I threw it in here as a reminder… find the answer in JB’s cards
17
Q
The middle ear contains the ____ ____ :
They transmit vibratory motions of the eardrum to the oval window
A
auditory ossicles
18
Q
The ossicles are named for their shapes:
A
Malleus (hammer)
Incus (anvil)
Stapes (stirrup)
19
Q
(hammer)
A
Malleus
20
Q
(anvil)
A
Incus
21
Q
(stirrup)
A
Stapes
22
Q
Auditory ossicles:
The handle of the ____ is secured to the internal surface of the eardrum
The incus articulates with the….
The base of the stapes fits into the __ ___
A
malleus
…malleus laterally and the stapes medially
oval window
23
Q
The handle of the malleus is secured to the…
A
… internal surface of the eardrum
24
Q
The incus articulates with the ___ laterally and the ____ medially
A
malleus laterally and the stapes medially
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The base of the ___ fits into the oval window
stapes
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What can be seen on the tympanic membrane with an otoscope?
The handle and lateral process of the malleus, and the long limb of the incus produce bulges that can be seen when viewing the tympanic membrane using an otoscope
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Muscles of the middle ear
Two small skeletal muscles attach to the ossicles:
Tensor tympani muscle
Stapedius muscle
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Tensor tympani muscle
Arises from the wall of the auditory tube and inserts into....
Limits movement and increases tension on the eardrum to....
Innervated by...
....the handle of the malleus
prevent damage from loud noises
.... the trigeminal nerve (V)
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Stapedius muscle
Originates from ?
Dampens ?
Innervated by ?
____ skeletal muscle in the body
Originates from the posterior wall of the middle ear cavity and inserts into the stapes
Dampens large vibrations of the stapes due to loud noises
Innervated by the facial nerve (VII)
Smallest skeletal muscle in the body
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slide 13 otoscopic view
slide 13 otoscopic view
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slide 14
slide 14
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An ear exam includes bilateral otoscopic inspection of both tympanic membranes. A normal tympanic membrane is
pearly gray and translucent
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The cone of light is a reflection from the otoscope’s illuminator. Termed the __ __, it is visible radiating ____ in a healthy ear, and can provide orientation
light reflex
anteroinferiorly
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Also called the auditory tube, or the pharyngotympanic tube
Consists of both bone and cartilage
Connects the middle ear with the nasopharynx
Eustachian tube
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Eustachian tube
Also called the ?
Consists of?
Connects the middle ear with the ?
Also called the auditory tube, or the pharyngotympanic tube
Consists of both bone and cartilage
Connects the middle ear with the nasopharynx
36
It is normally closed, but opens upon swallowing and yawning
Equalizes the pressure in the middle ear with the atmosphere
Without equalization, the ear would not be as effective, and pain or vertigo could also develop
Eustachian tube
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The Eustachian tube is also a route that pathogens may take from the...
...nose and throat to the middle ear
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The inner ear is also called the...
Two main divisions?
...labyrinth
```
Bony labyrinth (outer)
Membranous labyrinth (inner
```
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The bony labyrinth is a series of cavities in the petrous portion of the temporal bone comprising three areas
Semicircular canals
Vestibule
Cochlea
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The ___ ___ is a series of sacs and tubes inside the bony labyrinth, which has the same general form as the bony labyrinth
membranous labyrinth
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Cross-sectional representation of semicircular canal and contained semicircular duct
slide 21 of membranosu labryrinth
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Fluids in the inner ear?
Perilymph
Endolymph
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Chemically similar to cerebrospinal fluid
Surrounds the membranous labyrinth
Perilymph
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Within the membranous labyrinth
Has a high level of potassium ions (K+) which plays a role in generation of auditory signals
Endolymph
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slide 23 image
23
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is the oval central portion of the bony labyrinth
Vestibule
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Part of the membranous labyrinth is within the vestibule, and is composed of two sacs,
the utricle and saccule, connected by a duct
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The vestibule also contains the
oval window (vestibular window)
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The semicircular canals are three bony structures
At approximately right angles to each other
Named according to position:
Anterior (oriented vertically)
Posterior (oriented vertically)
Lateral (oriented horizontally)
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Semicircular canals :
A swollen enlargement called the
ampulla is at one end of each canal
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Semicircular canals :
Parts of the membranous labyrinth that are inside the semicircular canals are called
semicircular ducts; they connect to the utricle of the vestibule
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they connect to the utricle of the vestibule
semicircular ducts
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Caused by an increased amount of endolymph, which enlarges the membranous labyrinth
Symptoms include fluctuating hearing loss (due to distortion of the basilar membrane), roaring tinnitus (ringing in the ears), whirling vertigo (dizziness)
The hearing may be lost over a number of years
Ménière’s disease
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The vestibular branch of the vestibulocochlear nerve (cranial nerve VIII) consists of three nerves:
utricular, saccular, and ampullary
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The nerves synapse with receptors for equilibrium
They have both first-order sensory neurons and motor neurons:
Sensory neurons carry sensory information from the receptors
Motor neurons carry feedback signals to the receptors to modify their sensitivity
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Cell bodies of the sensory neurons are located in the
vestibular ganglia
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Cell bodies of the motor neurons are in the pons, and project to the
semicircular canals, saccule, and utricle
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The cochlea is a bony spiral canal
Its central supporting core is called the
modiolus
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The cochlea has a Y-shaped partition that forms three channels:
Scala media (AKA cochlear duct) in the forks of the Y
Scala vestibuli, on one side, ending at the oval window
Scala tympani, the other side, ending at the round window
60
The scala vestibuli and scala tympani contain
Scala vestibuli and scala tympani are separated by the stem of the “Y” except at the apex of the cochlea, where there is an opening called the...
perilymph
...helicotrema (“the hole in the spiral”) that joins them
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The ___ opens into the vestibule (hence its name)
scala vestibuli
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The _____ (AKA scala media) is between the wings of the “Y”
cochlear duct
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The scala media is a continuation of the membranous labyrinth into the cochlea
Membranes contain the perilymph within the different scalae:
Vestibular membrane of the scala vestibuli
Basilar membrane of the scala tympani
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The ____ (AKA organ of Corti) is on the basilar membrane, within the cochlear duct
It contains hair cells, which are the receptors for hearing
spiral organ
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It contains hair cells, which are the receptors for hearing
spiral organ (AKA organ of Corti)
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Hair cells of the spiral organ are in two groups:
Inner hair cells, arranged in a single row
| Outer hair cells, arranged in three rows
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A hair bundle is at the apical tip of each hair cell
Stereocilia comprise the “hairs” but they are actually...
...long microvilli
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Inner and outer hair cells synapse with both first-order sensory neurons and with motor neurons from the
cochlear branch of the vestibulocochlear nerve (cranial nerve VIII)
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Cell bodies of sensory neurons are in the
spiral ganglion of the cochlea
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The afferent fibers from the cochlea are myelinated dendrites of bipolar cells of the spiral ganglion. These bipolar neurons are the only neurons that have
a myelin sheath surrounding the cell body
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Cell bodies of motor neurons are in the ___, and project to hair cells of the spiral organ
pons
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The __ ___ projects over the hair cells, and is in contact with them
tectorial membrane
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Alternating high and low pressure regions of a medium (generally air)
Frequency = pitch
Amplitude = volume = intensity
Sympathetic vibrations
Sound
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Human hearing
| Frequency range
Most acute 500 to 5000 Hertz (cps)
| Audible range 20 to 20,000 Hz
75
Threshold defined as 0 dB at 1000 Hz, which is the point at which an average young adult can just distinguish sound from silence
Normal conversation is 60 dB
OSHA requires hearing plan when occupational noise levels exceed 90 dB
Rock concert and headphones produce >110 dB
Amplitude
76
STEPS IN HEARING
1. Sounds are directed into the external auditory canal by the auricle
2. Sound waves strike the eardrum, causing it to vibrate in sympathy
3. The vibrations are transmitted through the auditory ossicles, and somewhat magnified due to the mechanical relationships of the ossicles
4. The stapes vibrates, transmitting movements to the oval window, amplifying the energy due to differences between surface areas of eardrum and oval window
5. Oval window moves in and out, setting up fluid pressure waves in the perilymph
6. Pressure waves are transmitted from scala vestibuli to the scala tympani
7. Pressure waves deform the walls of the scala vestibuli and scala tympani pushing the vestibular membrane back and forth
7a. Pressure waves from the scala vestibuli and scala tympani create pressure waves in the endolymph inside the scala media (cochlear duct)
8. Pressure waves in the endolymph cause the basilar membrane to vibrate, moving the hair cells of the spiral organ against the tectorial membrane
9. Pressure waves cause vibration of the secondary tympanic membrane in the round window (no physiological consequence—fluid is incompressible)
77
Hair cells transduce mechanical vibrations into electrical signals by means of
mechanically gated ion channels
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of differing heights comprise the hair bundles at the apex of each hair cell
Stereocilia
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The tips of shorter stereocilia are connected by a __ __ __ to its taller stereocilium neighbor
tip link protein
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A mechanically-gated ion channel called a __ ___ is associated with the tip link proteins
transduction channel
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As stereocilia bend in the direction of the taller stereocilium to which they are connected, the tip links tug on
the transduction channels and open them
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Steps in hearing
The open channels allow ___ in the endolymph to enter the cell
cations
83
Cations enter and produce a __ __ __, which spreads along the membrane
depolarizing receptor potential
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Bending the stereocilia in the opposite direction closes transduction channels, allows repolarization, and
reduces neurotransmitter release from the hair cells
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Cell bodies of the first-order sensory neurons are in the spiral ganglia, and their axons comprise the
cochlear branch of the vestibulocochlear nerve
86
Axons of the cochlear branch synapse with neurons in the cochlear nuclei in the
medulla oblongata (on the same side—no decussation up to this point)
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Some axons from the cochlear nuclei decussate in the medulla and ascend in the lateral lemniscus on the opposite side, where they terminate in the
inferior colliculus of the midbrain
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Other axons from the cochlear nuclei end in the __ ___ __ in the pons on each side. These also ascend in the lateral lemniscus tracts on both sides, and end in the inferior colliculi
superior olivary nucleus
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Slight differences in the timing of nerve impulses arriving from each ear at the superior olivary nuclei enable us to
determine the direction of sounds
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Other axons from the cochlear nuclei end in the superior olivary nucleus in the pons on each side. These also ascend in the __ and end in
lateral lemniscus tracts on both sides, and end in the inferior colliculi
91
From each inferior colliculus, nerve impulses are conveyed to the ___________________, then to the primary auditory area of the cerebral cortex
medial geniculate nucleus of the thalamus
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From each inferior colliculus, nerve impulses are conveyed to the medial geniculate nucleus of the thalamus, then to the
primary auditory area of the cerebral cortex
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may be caused by allergy, high or low blood pressure (blood circulation problems), a tumor, diabetes, thyroid problems, injury to the head or neck, as well as a variety of medications including anti-inflammatory medicines, antibiotics, sedatives, antidepressants, and aspirin
Tinnitus
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The exact mechanism that causes tinnitus is not known. Younger people tend to have tinnitus as a result of exposure to loud noise. Older people who experience tinnitus often have a certain amount of hearing impairment related to the natural aging process
cool
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Exceptionally loud noises damage stereocilia, causing them to mistakenly continue sending sound information to the auditory nerve as they move randomly in a state of irritation.
Sometimes tips of some stereocilia break off
Ringing is temporary because the tips grow back within about 24 hours
Unlike many other forms of tinnitus, this form has a known cause
Ringing due to loud noises
96
Deafness is significant or total hearing loss
Two broad types:
Sensorineural deafness, due to damage or disease of the sensorineural pathway (hair cells, cochlear branch of cranial nerve VIII)
Conduction deafness (conductive deafness), caused by impairment of mechanisms in the external and middle ear (otosclerosis (deposition of new bone around the oval window)), impacted cerumen, eardrum injury, stiffening of the joints of the auditory ossicles
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due to damage or disease of the sensorineural pathway (hair cells, cochlear branch of cranial nerve VIII)
Sensorineural deafness,
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caused by impairment of mechanisms in the external and middle ear (otosclerosis (deposition of new bone around the oval window)), impacted cerumen, eardrum injury, stiffening of the joints of the auditory ossicles
Conduction deafness (conductive deafness),
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Exposure to loud noises damages hair cells of the cochlea
Continued exposure to high-intensity sounds is a cause of deafness
Noise-induced deafness
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The cochlea has the ability to produce sounds, which are termed
otoacoustic emissions
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They are usually inaudible, but can be picked up by a sensitive microphone next to the eardrum
Cause by vibrations of the outer hair cells in response to signals from motor neurons and to sound waves
otoacoustic emissions
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Otoacoustic emissions
The vibrations of the outer hair cells set up a traveling wave that goes back toward the ____, causing the eardrum to vibrate
stapes
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This provides a fast, inexpensive, noninvasive way to screen newborns for hearing defects, since in deaf babies ______ are not produced, or are greatly reduced in size
otoacoustic emissions
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Equilibrium
Two types of equilibrium (balance) exist
Static equilibrium—the maintenance of the position of the body (mainly the head) relative to the force of gravity
Dynamic equilibrium—maintenance of body position (mainly the head) in response to sudden movements
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the maintenance of the position of the body (mainly the head) relative to the force of gravity
Static equilibrium—
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maintenance of body position (mainly the head) in response to sudden movements
Dynamic equilibrium—
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Dynamic equilibrium
_____ is a complex of strange eye movements that occurs during and immediately after rotational movement
Nystagmus can be accompanied by vertigo
Vestibular nystagmus
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Equilibrium pathway
Cell bodies of the first-order sensory neurons are in the __ __, and their axons comprise the...
vestibular ganglia
...and their axons comprise the vestibular branch of the vestibulocochlear nerve
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Equilibrium pathway
Most of the axons of the vestibular branch synapse with neurons in the vestibular nuclei in the....
...medulla oblongata (on the same side—no decussation up to this point)
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Equilibrium pathway
Most of the axons of the vestibular branch synapse with neurons in the vestibular nuclei in the....
...medulla oblongata (on the same side—no decussation up to this point)
111
Equilibrium pathway
The remaining axons enter the cerebellum through the....
The ___ and ____ are connected by bidirectional pathways
....inferior cerebellar peduncles.
The cerebellum and vestibular nuclei are connected by bidirectional pathways
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Equilibrium pathway
The remaining axons enter the cerebellum through the....
The ___ and ____ are connected by bidirectional pathways
....inferior cerebellar peduncles.
The cerebellum and vestibular nuclei are connected by bidirectional pathways
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Equilibrium pathway
The vestibular nuclei integrate information from...
vestibular, visual, and somatic receptors, then send commands via a number of nuclei and tracts:
114
Equilibrium pathway
The vestibular nuclei integrate information from...
vestibular, visual, and somatic receptors, then send commands via a number of nuclei and tracts:
115
Motion sickness
Appears to be due to sensory input mismatch:
Within a moving vehicle the immediate frame of reference (the vehicle) is
stationary according to visual inputs
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Motion sickness
Appears to be due to sensory input mismatch:
A discrepancy arises when . . .
The surroundings are moving according to visual input
The vehicle is moving according to vestibular inputs (acceleration, deceleration, tilting, etc.)
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Motion sickness
Appears to be due to sensory input mismatch:
The brain receives conflicting information, and its “confusion” causes
motion sickness
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The receptor organs for equilibrium are called the vestibular apparatus, and include
Saccule
Utricle
Semicircular ducts (within the semicircular canals)
119
Walls of the utricle and saccule contain a small region called a ___?
___ it's horizontal in utricle
vertical in the saccule
macula
Macula is horizontal in the utricle
Macula is nearly vertical in the saccule
120
The maculae consist of two kinds of cells:
Hair cells, which are sensory receptors
Supporting cells, which produce a gelatinous glycoprotein layer called the otolithic membrane, that rests on the hair cells
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Hair cells are composed of hair bundles, having two types of hairs
Stereocilia (actually microvilli)
Kinocilium
One kinocilium per bundle
A true cilium
Longer than the longest stereocilia of the bundle
122
The stereocilia are connected by
tip links (same as in the cochlea)
123
A layer of calcium carbonate crystals, called ___, extends over the surface of the otolithic membrane
otoliths
124
Physiology of static equilibrium
When the head is tilted or accelerates, inertia causes the otolithic membrane to
slide over the hair cells, bending the hair bundles
125
Physiology of static equilibrium
Bending the hair bundles in one direction stretches the tip links, opening the mechanically-gated transduction channels, and producing
depolarizing receptor potentials and release of neurotransmitter
126
Physiology of static equilibrium
Bending the hair bundles in the other direction closes the __ and produces what?
transduction channels and produces repolarization
127
Physiology of static equilibrium
The maculae respond only to changes in ?
They adapt ___ ?
They do not report on unchanging head positions
The maculae respond only to changes in acceleration or velocity of head movement
They adapt quickly
They do not report on unchanging head positions
128
Dynamic equilibrium
The three semicircular ducts plus the saccule and utricle function in dynamic equilibrium (there are also visual and proprioceptor inputs, but these are not located in the
inner ear, so they are not generally discussed)
129
Dynamic equilibrium
Within the ampulla (dilated portion) of each duct is a small elevation called a crista (crista ampullaris)
Each crista contains
Hair cells
Supporting cells
Cupula, a mass of gelatinous material
130
Dynamic equilibrium
When the head moves the endolymph within the ampulla lags behind due to ___
This causes?
inertia
This causes the hair cells to bend, producing receptor potentials
131
Dynamic equilibrium
Receptor potentials lead to nerve impulses that pass along the
vestibular branch of the vestibulocochlear nerve (cranial nerve VIII)
132
Dynamic equilibrium
If the body continues to rotate at a constant rate, the endolymph eventually __ causing what?
If the body stops suddenly....
catches up, and stimulation of the hair cells ends
If the body stops suddenly, the endolymph keeps moving
