chapter 17- nervous system: special senses Flashcards
1
Q
why is it unusual that the olfactory epithelium contains basal cells that replace the olfactory receptor cells every 60 days?
A
olfactory receptors are neurons & most neurons are not replaced & must function for a lifetime
2
Q
olfactory glands produce what?
A
mucus
3
Q
olfactory cilia are covered in what which each function to bind a few different odorant molecules to trigger olfactory signaling through G protein activation?
A
odorant binding proteins
4
Q
the axons of the olfactory receptor cells synapse on the what?
A
olfactory bulbs
5
Q
what deficiency could result in the condition of anosmia because it is necessary for stem cell division?
A
zinc
6
Q
the molecules that can be bound by the chemoreceptors on gustatory hairs are called?
A
tastants
7
Q
there are five primary taste sensations: sweet, sour, salty, bitter and what else?
A
umami
8
Q
where is the gustatory cortex located?
A
insula of cerebrum
9
Q
processing of gustatory information in the hypothalamus and limbic system results in?
A
emotional reaction to flavors
10
Q
why do you taste salt and sour more rapidly than sweet?
A
salt & sour receptors are chemically gated ion channels that release neurotransmitters rapidly (sweet requires activation of G proteins & second messengers which is slower)
11
Q
why do you notice new tastes easily but not the same taste for a prolonged
period?
A
central adaptation of the gustation pathways
12
Q
mame the bump in the medial corner of the eye that contains sebaceous &
sudoriferous glands
A
lacrimal caruncle
13
Q
what is the transparent mucous membrane that
covers the anterior surface of the eye? it can become infected and inflamed
resulting in “pink eye”
A
conjunctiva
14
Q
what is the condition of being born with weakness of the external eye muscles resulting in “cross eyes”?
A
strabismus
15
Q
the white fibrous tunic that makes up most of the outside of the eyeball is the
what? it’s continuous with the epineurium of the optic nerve
A
sclera
16
Q
why are there a lot of pain receptors in your cornea?
A
defense to avoid injury (clear collagen can only be made during embryonic development, injury after birth will result in opaque scars)
17
Q
The hole in the middle of the iris that allows light to enter the eye is called the?
A
pupil
18
Q
why is the optic disc a “blind spot”?
A
no photoreceptors
19
Q
the part of your retina with the highest concentration of photoreceptors is the
what? the focal point directly behind the center of
the lens
A
macula lutea
20
Q
the posterior segment of the eyeball is filled with a clear gel called?
A
vitreous humor
21
Q
aqueous humor is constantly produced by the what?
A
ciliary body
22
Q
why does a red object appear red?
A
because it reflects the red wavelengths of the light (~750nm) to the eye
23
Q
the rounder a lens what is the focal distance?
A
shorter
24
Q
without corrective lenses, a person with what naturally refracts light to a point behind the retina?
A
hyperopia
25
what is the visual pigment that is composed of retinal from vitamin A and the protein opsin?
rhodopsin
26
the photoreceptors called what absorb any wavelength
between 380nm and 750nm and when activated will result in perceptions of
shades of gray?
rods
27
what is the function of horizontal cells of the retina?
to facilitate or inhibit the synapse of photoreceptor cells on the bipolar cells
28
what is the purpose of visual signaling being routed to the suprachiasmatic
nucleus of the hypothalamus?
to set your sense of a 24-hour day, set circadian rhythms
29
the external auditory canal begins at the auricle and ends at the what?
tympanic membrane
30
the three auditory ossicles are the malleus, incus and what else?
stapes
31
what is the function of the auditory tube?
allow for equalization of pressure in the middle ear
32
what is the collective function of the tensor tympani and stapedius muscles?
reduce amount of sound energy being transmitted into inner ear
33
in what fluid-filled inner ear structure are the hearing receptor cells located?
cochlea
34
the total frequency range of human hearing is 20 to what Hz, however we lose the higher frequencies with age?
20,000
35
hair cells function as what? When the stereocilia are touched or bent the cell depolarizes?
mechanoreceptors
36
what is the purpose of auditory signaling being processed in the inferior colliculi of the mesencephalon?
initiate auditory reflexes
37
having an accident with loud sound where all the stereocilia get broken off your hair cells would result in what?
sensorineural deafness
38
the receptors for static equilibrium are what housed in the vestibule?
maculae
39
the receptors for dynamic equilibrium are the what housed in the semicircular canals?
crista ampullaris
40
equilibrium signaling enters the brain through the what nerve?
vestibulocochlear nerve (cranial nerve VIII)
41
if you spin around, when you stop the endolymph in vestibular complex /apparatus will keep spinning for a while which will cause movements of
the eyes. this phenomenon is called?
nystagmus
42
five special senses:
smell, taste, sight,
hearing, equilibrium
43
special senses
-5 of them
-all involve special sensory receptors
-distinct receptor cells
-housed in complex sensory organs or unique epithelial structures
44
olfaction (smell)
-olfactory organs = olfactory epithelium
-housed in nasal cavity, inferior surface of cribriform plate and superior nasal conchae
45
olfactory receptor cells (olfactory epithelium component)
-bipolar neurons
-chemoreceptors
-bind and respond
to odorants (smell
chemicals)
46
supporting cells (olfactory epithelium component)
simple columnar epithelium
47
basal cells (olfactory epithelium component)
-stem cells
-replace olfactory receptor cells every 60 days
48
lamina propria (olfactory epithelium component)
-areolar CT
-supports epithelium and neurons
-contains olfactory glands for mucus
production: mucus covers surface of olfactory epithelium
49
olfactory receptor cells
-single dendrite at apical
surface of epithelium
-dendrite ends in knob
covered in olfactory cilia
-cilia extend into mucus
-odorant binding proteins on
cilia bind chemical odorant molecules that have diffused into mucus
-each receptor cell has only one type of odorant binding protein but each protein
binds several odorants
-axon from each cell passes
through olfactory foramina
of cribriform plate to synapse on olfactory bulbs (axons = olfactory nerves)
50
how many olfactory receptors do humans have?
~1000 different odorant binding proteins, distinguish ~10,000 different
odors
51
olfactory signaling: 1-3
1. odorant binds odorant binding protein on olfactory receptor cell cilia in mucus
2. G-protein is activated which activates adenylate cyclase
3. ATP is converted into cAMP
52
olfactory signaling: 4-6
4. cAMP causes sodium channels to open resulting in depolarization
5. if threshold is reached an action potential is transmitted to olfactory bulbs
6. the nervous impulse from olfactory bulbs travels down olfactory tracts to be routed to olfactory cortex of temporal lobe of cerebrum for interpretation & hypothalamus & limbic systems to elicit emotional response to odors
53
olfactory signaling
-signaling can also stimulate reflexes for salivation, digestive secretion, sneezing & coughing
-olfactory pathways converge & are subject to rapid central adaptation
54
uncinate fits (olfactory disorder)
-olfactory hallucinations
-distorted sense of smell due to damage of olfactory pathways, epilepsy, or migraines
55
anosmias
-“without smells”
-loss of sense of smell
-due to head injury, inflammation, age, or zinc
deficiency (zinc necessary for growth of basal cells to
replace receptor cells)
56
gustation (taste)
-gustation organs = taste buds
~10,000 total
-most located on tongue associated with lingual papillae (friction bumps)
-small number on oral surfaces: soft palate, inner cheeks, pharynx, epiglottis
57
taste bud components
-50-100 epithelial cells
of two types: gustatory & basal cells
-taste buds located deep in tongue epithelium with gustatory hairs protruding into taste pore
58
gustatory cells (taste bud component)
-taste receptor cells
-in various stages of maturity
-gustatory hairs in mature
-gustatory hairs bind tastants (taste chemicals)
-each gustatory cell is wrapped in sensory
dendrites
59
gustatory hairs
long microvilli that function as chemoreceptors
60
basal cells (taste bud component)
-stem cells
-replace gustatory
cells every 7-10 days
61
5 primary taste sensations
1. sweet: sugars, alcohols, some amino acids
2. sour: acids
3. salty: metal ions
4. bitter: alkaloids
5. umami “delicious”: amino acid glutamate (beef taste) (MSG binds this)
62
tastes and cravings drive dietary needs:
-umami -> proteins
-sugar & salty -> carbs & minerals
-sour -> vitamin C
-tastes also protect: most toxins are bitter
63
gustatory signaling 1-3
1. tastant must be dissolved in saliva & diffuse into taste pores
2. tastant binds chemoreceptors on gustatory hairs of a mature gustatory cell
3. gustatory cell releases neurotransmitters to signal sensory dendrites around it
64
gustatory signaling 4-5
4. if threshold is reached, action potentials will be transmitted along facial nerve (VII), glossopharyngeal nerve (IX), or vagus nerve (X), to solitary nucleus of medulla oblongata
5. info is passed to thalamus for screening & routing to:
a. gustatory cortex in insula of cerebrum (80% of taste is smell)
b. hypothalamus & limbic system to elicit emotional reaction to taste
65
gustatory signaling
-signaling can trigger reflexes to stimulate digestive activity
-threshold necessary for stimulation of neural pathways varies with receptor & person but everyone is generally more sensitive to bitter & acid
-gustation pathways undergo rapid central adaptation
66
salt & sour receptors are chemically gated ion channels (gustatory signaling):
they release neurotransmitters rapidly upon binding tastant
67
sweet, bitter & umami receptors are G-proteins that work through second messengers (gustatory signaling):
release of neurotransmitter and slower
68
vision (sight)
vision organs = eyes
-70% of total body receptors
-50% of cerebral cortex involved in vision processing
69
accessory structures of the eye
to protect or aid function of eye
70
eyebrows (accessory structure of the eye)
-shade from the sun
-prevent perspiration trickling in
71
eyelids (accessory structure of the eye)
-blink via reflexes: every 3-7sec or in response to threat
-keep eye surface lubricated & free of dust by spreading glandular secretions
72
lacrimal caruncle (part of eyelid -> accessory structure of the eye)
-medial corner
-contains sebaceous & sudoriferous glands that produce secretions to lubricate eye surface
73
eyelashes (part of eyelid -> accessory structure of the eye)
-hairs along free margin of each lid
-hair root plexus receptors trigger defensive blinking
-prevent entry of foreign material into eye
74
tarsal glands (part of eyelid -> accessory structure of the eye)
-associated with eyelashes
-modified sebaceous glands that produce oily secretion to prevent lids from sticking
75
conjunctiva (accessory structure of the eye)
-transparent mucous membrane
-covers anterior surface of eye & interior surface of lids
-produces lubricating mucus to keep eyes moist
-contains tiny capillaries
76
conjunctivitis
inflammation of conjunctiva due to microbial infection (pink eye)
77
lacrimal apparatus (accessory structure of the eye)
-lacrimal gland located lateral & superior to eye
-produces lacrimal fluid to cleanse & protect eye surface
-lacrimal fluid (tears) include mucus, antibodies & lysozymes
-lacrimal fluid from gland flows down across eye surface, is collected in lacrimal canaliculi in medial corner of eye & is drained to nasal cavity via nasolacrimal duct
78
mucus (tears of lacrimal apparatus ->accessory structure of the eye)
lubrication of eye
79
antibodies (tears of lacrimal apparatus ->accessory structure of the eye)
immune defense against microbes
80
lysozyme (tears of lacrimal apparatus ->accessory structure of the eye)
enzyme that lyses (breakdowns) bacteria
81
extrinsic eye muscles (accessory structure of the eye)
-six strap-like skeletal muscles that originate on orbit & insert on outer surface of eye
-motor units consist of only 2-12 fibers
-function to provide precise & rapid movement of eyes
82
diplopia
-“double vision”
-failure to coordinate movement of eyes resulting in two different visual fields
-due to paralysis, weak muscles, intoxication
83
strabismus
-“cross-eyed”
-congenital weakness of external eye muscles
-treated with exercises or surgery
84
the eye
-fluid-filled sphere
-wall consists of three layers:
1. outer fibrous tunic
2. intermediate vascular tunic
3. inner neural tunic
-interior divided into two cavities (anterior, posterior) by the lens
-cavities contain fluids called humors: maintain shape of eye
85
fibrous tunic (outer wall of the eye)
-dense fibrous CT
-avascular
86
sclera "white of eye" (part of fibrous tunic of eye)
-posterior 5/6ths
-functions to maintain eye shape and as attachment for eye muscles
-continuous with epineurium of optic nerve & dura mater of brain
87
cornea (part of fibrous tunic of eye)
- anterior 1/6th
- clear, allows light to enter eye
- high concentration of pain receptors
- damage = scarring = inhibit vision
88
corneal transplant
due to lack of blood
supply there are no immune cells, no need to tissue type match
89
vascular tunic = uvea (intermediate wall of the eye)
-contains blood & lymphatic vessels for all three tunics
-three regions: choroid, ciliary body, iris
90
choroid (part of vascular tunic of eye)
-lines posterior 5/6ths
-pigmented dark brown by melanocytes to prevent light scatter
91
ciliary body (part of vascular tunic of eye)
-circular smooth muscles that function to focus lens & center it posterior to pupil
-attached to lens by suspensory ligaments
-secretes fluid that fills anterior chamber of
eye
92
iris (part of vascular tunic of eye)
-anterior portion of uvea
-has central opening called pupil
-smooth muscle + elastic fibers
-regulate pupil size to control light level entering eye:
-parasympathetic stimulation = circular muscles contract -> pupil size decreases
-sympathetic stimulation = radial muscles contract -> pupil size increases
93
what does the color of the iris depend on?
-color variations depend on amount & location of melanin:
-more on both sides = brown
-less on posterior only = blue
94
neural tunic = retina (inner wall of eye)
-two parts: pigmented layer & neural layer
-majority of retina contains rods only
95
pigmented layer (layer of neural tunic of eye)
-melanin-rich simple cuboidal epithelium in contact with choroid
-absorbs light to prevent scatter
-stores Vitamin A
-capable of phagocytosis
96
neural layer (layer of neural tunic of eye)
-5 types of neurons: photoreceptors, horizontal cells, bipolar cels, amacrine cells & ganglion cells
97
photoreceptors (neurons in neural layer of neural tunic of eye)
-detect light photons
a. rods = dim light, no color, peripheral vision
b. cones = color, sharp vision
98
horizontal cells (neurons in neural layer of neural tunic of eye)
visual proccessing
99
bipolar cells (neurons in neural layer of neural tunic of eye)
transmit info from photoreceptors
100
amacrine cells (neurons in neural layer of neural tunic of eye)
visual processing
101
ganglion cells (neurons in neural layer of neural tunic of eye)
transmit visual info to brain, axons exit eye as optic nerve
102
optic disc
“blind spot”: where axons bundle to form optic nerve, no photoreceptors
103
macula lutea
focal point directly behind
center of lens, contains all the cones of the retina (also has rods)
104
fovea centralis
center of macula, contains
cones only, point of sharpest vision
105
macular degeneration
-photoreceptors in macula die due to poor blood supply
-patient has only grainy peripheral vision
106
detached retina
-portion of retina separates from choroid
-due to sudden head jerk
-photoreceptors without blood supply die
107
posterior cavity of the eye
-posterior to lens
-filled with vitreous humor: clear gel formed in embryo, maintained throughout life
108
functions of the posterior cavity of eye:
-support retina in contact with choroid while allowing light to pass through
-provide intraocular pressure to counteract extrinsic eye muscles
109
floaters
small moving spots caused by cell debris in vitreous humor
110
anterior cavity of eye
-anterior to lens
-filled with aqueous humor, constantly produced by ciliary body
-aqueous humor diffuses through both cavities, reabsorbed at the scleral venous sinus at base of iris
111
functions of aqueous humor (produced by ciliary body -> anterior cavity of eye)
-maintain consistent intraocular pressure
-diffusion medium for lens and cornea
112
glaucoma
failure to drain aqueous humor, pressure compresses retina & optic nerve
resulting in vision loss
113
lens of eye
-transparent, flexible, avascular disc
-cells with no organelles, contain crystallin proteins only
-allows precise focusing of light on retina
-held in place directly behind pupil by suspensory ligaments which attach lens to ciliary body
114
cataracts
-clouding of the lens due to clumping of crystallins
-due to age, diabetes, smoking, sun
-corrected by lens replacement or laser removal of crystalline
115
visual physiology
-visible light
-can be separated by wavelength into visible
spectrum of colors from violet (380nm) to red (750nm)
-eye detects photons reflecting off objects
-at constant speed light travels in straight line
-when it passes through new object, speed changes & light bends/refracts
-more curved the surface the greater the refraction
-a lens has a curve that functions to refract all light to a single focal point
116
visible light
electromagnetic radiation,
380-750nm, composed of photons
117
color (visual physiology)
wavelengths being reflected
118
focal distance
distance between lens and its
focal point, depends on:
1. distance from object to lens (increases as
object gets closer)
2. shape of lens (rounder = shorter)
119
focusing light on the retina:
-light entering eye is refracted by cornea, lens
& humors
-refraction by cornea & humors constant
-accommodation involved
-at rest lens focuses on macula lutea from objects 20ft away
-to focus on closer objects, ciliary body compresses lens to shorten focal distance
-flexibility of lens only allows focus up to 4in from eye
120
accommodation
refraction by lens can be altered by changing
its shap
121
presbyopia
loss of accommodation with age
122
myopia (near sighted)
the lens refracts light to focal point in front of retina
-cannot focus on distant objects
-accommodation allows focus on near
123
hyperopia (far sighted)
the lens refracts light to
focal point behind retina
-accommodation maxed out to focus on distant objects preventing focus of near
124
astigmatism
unequal curvature of cornea or lens (part out of focus, part in)
125
radial keratotomy (Lasik)
reshape cornea
126
visual acuity (you@20ft / normal@ X ft):
20/20: normal
20/15: better
20/200: < = legally blind
127
photoreception
-process by which eye detects light
-requires visual pigments in photoreceptors
-discs constantly replaced: newly added at bottom, old shed at tip, phagocytosed by
pigmented layer
128
photoreceptors (rods & cones)
-neurons with two parts: rods & cones
129
rods
long, slender
130
cones
short, tapered
131
inner segment of photoreceptors
soma and processes
that synapse on a bipolar cell
132
outer segment of photoreceptors
-contacts pigmented layer
-composed of discs of membrane containing visual pigments
133
visual pigment
-rhodopsin, 2 parts: retinal & opsin
-used rhodopsin recycled and replaced
-absorption spectra of all three overlaping of cones allows perception of intermediate hues from differential activation of more than one type of cone
134
retinal (visual pigment)
-light-absorbing
-from Vitamin A
-binds photons &
changes shape
135
opsin
-protein
-inactive when bound to retinal
-photons -> retinal isomerizes cis -> trans, retinal releases opsin
136
photobleaching
-trans retinal not bound to
opsin, cannot respond to photons
-leaves lingering images until rhodopsin is replaced
137
retinal responds to different wavelengths & thresholds of photons depending on the opsin bound:
a. rods: absorb all (380-750nm)
-activated by dim light
-info perceived as shades of gray
b. cones: specific, 3 types
-require bright light for activation
1. blue: peak response @ 420nm
2. green: peak @ 530nm
3. red: peak @ 560nm
138
color blindness
-congenital, X-linked
-lack one or more types of cone
-red-green most common
-8% of all men have some degree
139
visual signaling 1: in the dark
cGMP opens sodium channels causing constant depolarization to -40mV, depolarization causes neurotransmitter release
140
visual signaling 2: light photon strikes rhodopsin
a. cis retinal -> trans retinal + release of opsin
b. opsin activates phosphodiesterase (PDE)
c. PDE breaks down cGMP, Na+ channels close
d. photoreceptor cells hyper polarize to -70mV, neurotransmitter release stops
e. lack of neurotransmitter triggers EPSP on postsynaptic bipolar cell
f. synapse is facilitated or inhibited by horizontal cells
g. facilitated bipolar cells trigger EPSP on ganglion cells
h. synapse is facilitated or inhibited by amacrine cells
i. facilitated ganglion cells trigger an action potential
141
visual signaling 3
impulse travels down optic nerve to be diverged to three locations:
1. superior colliculi of midbrain to initiate visual reflexes
2. suprachiasmatic nucleus of hypothalamus to set circadian rhythms
3. thalamus for screening & routing to primary visual cortex in occipital lobes & visual association areas throughout cerebral cortex for interpretation
142
visual signaling
-rods undergo extensive convergence in retina: 130 million rods -> 6million bipolar cells -> 1million ganglion cells (M cells) = vision grainy & blurred
-cones show little convergence to their ganglion cells (P cells) resulting in perception of color, fine detail & crisp distinct edges
143
hearing & equilibrium
-hearing and equilibrium organs = ears
-involve mechanoreceptors: hair cells with stereocilia, housed in inner ear
-the ear: 3 major regions
144
external ear (major part of the ear):
a. pinna/auricle
b. external auditory canal
c. tympanic membrane
145
pinna/auricle (external ear -> major part of the ear)
-projection of skin-covered elastic cartilage
-functions to funnel sound into external auditory canal
146
external auditory canal (external ear -> major part of the ear)
-from auricle to tympanic membrane
-lined with hairs & ceruminous glands: secrete cerumen
-both prevent entry of foreign material
147
tympanic membrane (external ear -> major part of the ear)
-boundary between external & middle ear
-composed of CT & epithelium
-transmits sound energy from air to auditory ossicles
148
middle ear (major part of the ear)
-air-filled mucosa-lined chamber between
tympanic membrane & oval window
-houses auditory ossicles: malleus, incus, stapes
-ossicles amplify and transmit sound energy from tympanic membrane (external ear) to oval window (inner ear)
149
otitis media
-middle ear infection
-usually caused by migration of throat infection
-inflammation can rupture tympanic membrane
150
middle ear contains two muscles to protect ear from loud sounds:
1. tensor tympani
2. stapedius
151
tensor tympani (muscle of the middle ear)
-inserts on malleus
-contraction inhibits vibrations of tympanic
membrane to dampen sound
152
stapedius (muscle of the middle ear)
-inserts on stapes
-contraction inhibits vibration of oval window reducing sound conduction to
inner ear
153
inner ear (major part of the ear)
-located in temporal bone, posterior to eye
-consists of network of fluid filled chambers
-fluid functions to transmit sound or movement energy to mechanoreceptor cells
- 2 parts: semicircular canals & cochlea
154
semicircular canals (inner ear -> major part of the ear)
-3 total, one in each plane, connected to vestibule
-contains vestibular apparatus: houses equilibrium receptor cells
-filled with endolymph
155
cochlea (inner ear -> major part of the ear)
-spiral conical chamber
-begins at oval window, ends at round window
-contains organ of Corti: houses hearing receptor cells
-filled with perilymph
156
sound (hearing)
pressure disturbance that moves as a
wave with two properties: frequency & intensity
157
frequency (sound -> hearing)
-wavelength
-measured as waves /sec: Hertz (Hz)
-perceived as pitch
-humans: 20-20,000 Hz
-"frequency = "pitch
158
intensity (sound -> hearing)
-amplitude
-measured in decibels (dB)
-perceived as volume
-humans: 0-120dB without pain
-frequent/long-term exposure to sounds >90dB can result in hearing loss (shear stereocilia off hair cells)
159
organ of corti
-spirals around inside of cochlea
-consists of hair cells sandwiched between a
superior tectorial membrane & an inferior basilar membrane
-hair cells held in place by supporting cells & surrounded by perilymph
-contains stereocilia
-contains mechanoreceptor
-each hair cell synapses with
a sensory neuron
160
stereocilia (part of organ of corti)
hair cells covered in apical
projections
161
mechanoreceptor (part of organ of corti)
stereocilia detect pressure
or distortion, hair cell
162
sound transmission & auditory signaling 1-3
1. sound waves in the air enter the external auditory canal & vibrate tympanic membrane
2. tympanic membrane vibrates malleus which vibrates the incus which vibrates stapes
3. stapes vibrate oval window (20x greater volume = amplification of sound) which creates waves in perilymph in cochlea
163
sound transmission & auditory signaling 4-6
4. pressure waves distort basilar membrane causing hair cell cilia to brush against tectorial membrane
5. flexion of stereocilia opens ion channels causing depolarization of hair cell
6. EPSP is transmitted to sensory neurons of spiral ganglion
164
sound transmission & auditory signaling 7
-axons of spiral ganglion transmit action potentials along vestibulocochlear nerve to be diverged to:
a. inferior colliculi of mesencephalon to initiate auditory reflexes
b. thalamus for screen & routing to auditory cortex in temporal lobe of cerebrum for interpretation
165
sound transmission & auditory signaling
-pitch is determined by regions of basilar membrane vibrated: low frequency sounds travel further into cochlea
-volume is determined by # of hair cells stimulated: high volumes stimulate more hair cells
166
deafness
loss of hearing
167
conduction deafness
reduced ability to
conduct sound to perilymph (e.g. perforated tympanic membrane, otitis media, otosclerosis)
168
sensorineural deafness
loss of function of hair cells or neurons in auditory pathway
169
tinnitus
-phantom cochlear noise
-ringing caused by inappropriate stimulation of auditory pathway due to
inflammation, nerve damage,
medications
170
equilibrium & orientation
-equilibrium receptors = the vestibular apparatus
-housed in the semicircular canals & vestibule
-equilibrium receptors are designed to detect only changes in linear & angular
movements will adapt quickly
-the sense of equilibrium depends on info from the equilibrium receptors + vision + proprioception
171
-equilibrium receptors divided into 2 functional categories:
1. static equilibrium (linear)
2. dynamic equilibrium (angular)
172
nystagmus
-rotational eye movements that occur following a spin
-eyes search for a focal point until endolymph comes to rest
173
vertigo
perception of motion due to
inappropriate stimulation along the equilibrium pathway
174
motion sickness
-results when the mesencephalon receives
conflicting information about
equilibrium:
-visual cues indicate body is stationary but inner ear indicates movement
175
static equilibrium (equilibrium receptor)
-receptors = maculae, housed in vestibule
-respond to linear acceleration forces
-maculae components
176
maculae components of static equilibrium (equilibrium receptor):
1. supporting cells: simple columnar epithelium
2. hair cells = equilibrium receptor
-apical surface has hairs consisting of many stereocilia & long kinocilium
3. otolithic membrane:
- jelly-like membrane containing otoliths (stones of calcium carbonate)
- has cilia of hair cells embedded in it
177
static equilibrium signaling 1-3
1. hair cells in maculae release low levels of neurotransmitters continuously
2. upon acceleration, otoliths lag distorting otolithic membrane
3. membrane distortion bends stereocilia & kinocilia of hair cells
178
static equilibrium signaling 4-6
4. signaling from hair cells increases
5. EPSPs reach threshold on neuron of vestibular ganglion
6. dynamic equilibrium routes messages to CNS
179
dynamic equilibrium (equilibrium receptor)
-receptors = cristae ampullaris housed in semicircular canals (1 in each canal/plane)
-respond to angular/rotational movements
-crista ampullaris components
-each crista ampullaris is surrounded by endolymph which fills semicircular canals
180
crista ampullaris of dynamic equilibrium (equilibrium receptor)
1. supporting cells: simple columnar epithelium
2. hair cells = equilibrium receptor
-apical surface has hair consisting of many stereocilia & on long kinocilium
3. cupula: jelly-like mass that contains cilia of hair cells
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dynamic equilibrium signaling 1-4
1. hair cells in crista ampullaris constantly signal at low levels
2. rotation movement causes waves in endolymph
3. waves strike cupula thus bending stereocilia & kinocilia of hair cells
4. hair cells signal more rapidly
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dynamic equilibrium signaling 5-6
5. EPSPs reach threshold on neurons of vestibular ganglion
6. informative from both macular & crista ampullaris is passed on to CNS via vestibulocochlear nerve to diverge:
a. cerebellum: coordinated equilibrium with visual & proprioceptor input to direct somatic activity to maintain balance
b. vestibular nuclei in midbrain: coordinates equilibrium, vision & proprioception to direct head & eye movements to maintain line of vision forward
