Chapter 17 Flashcards
1
Q
Olfaction
A
Sense of smell.
2
Q
Olfactory epithelium
A
Where the receptors for olfaction are located. Occupies the superior part of the nasal cavity, covering the inferior surface of the cribriform plate and extending along the superior nasal concha.
3
Q
What three kinds of cells does the olfactory epithelium consist of?
A
- Olfactory receptor cells
- Supporting cells
- Basal cells
4
Q
Olfactory receptor cells
A
Are the first-order neurons of the olfactory pathway. Are bipolar neurons with an exposed, knob-shaped dendrite and an axon projecting through the cribriform plate that ends in the olfactory bulb.
5
Q
Olfactory cilia
A
Extend from the dendrites of olfactory receptors. Sites of olfactory transduction.
6
Q
Olfactory receptor
A
Proteins that detect inhaled chemicals.
7
Q
Odorants
A
Chemicals that bind to and stimulate the olfactory receptors in the olfactory cilia.
8
Q
Supporting cells (of the olfactory epithelium)
A
Columnar epithelial cells of the mucous membrane that line the nose. They provide physical support, nourishment, and electrical insulation for the olfactory receptor cells and help detoxify chemicals that come in contact with the olfactory epithelium.
9
Q
Basal cells (of the olfactory epithelium)
A
Stem cells located between the bases of the supporting cells. They continually undergo cell division to produce new olfactory receptor cells, which live for only about two months before being replaced.
10
Q
Olfactory glands
A
AKA Bowman’s glands; produce mucus that is carried to the surface of the epithelium by ducts. The secretion moistens the surface of the olfactory epithelium and dissolves odorants so that transduction can occur.
11
Q
Olfactory transduction
A
Binding of an odorant molecule to an olfactory receptor protein activates a G protein and adenylyl cyclase, resulting in the production of cyclic AMP (cAMP). Cyclic AMP (cAMP) opens cation channels, and Na+ and Ca2+ ions enter the olfactory receptor cell. The resulting depolarization may generate an action potential, which propagates along the axon of the olfactory receptor cell.
12
Q
Adaptation
A
Decreasing sensitivity.
13
Q
Gustation
A
Sense of taste. Is a chemical sense.
14
Q
What are the five primary tastes? And how are each of the tastes produced?
A
- Salty: is caused by the presence of sodium ions (Na+) in food.
- Sour: is produced by hydrogen ions (H+) released from acids.
- Sweet: is elicited by sugars such as glucose, fructose, and sucrose and by artificial sweeteners such as saccharin, aspartame, and sucralose.
- Bitter: is caused by a wide variety of substances, including caffeine, morphine, and quinine. In addition, many poisonous substances like strychnine have a bitter taste.
- Umami: described as “meaty” or “savory.” Is elicited by amino acids (especially glutamate) that are present in food.
15
Q
Taste bud
A
Where the receptors for taste are located. Most are found on the tongue, and some are found on the soft palate, pharynx, and epiglottis.
16
Q
What three kinds of epithelial cells make up taste buds?
A
- Supporting cells
- Gustatory cells
- Basal cells
17
Q
Supporting cells (of the taste buds)
A
Surround about 50 gustatory receptor cells in each taste bud.
18
Q
Gustatory receptor cells
A
At their base they synapse with dendrites of the first-order neurons that form the first part of the gustatory pathway. The dendrites of each first-order neuron branch profusely and contact many gustatory receptor cells in several taste buds. Has a life span of about 10 days.
19
Q
Gustatory microvilli
A
AKA gustatory hairs; project from each gustatory receptor cell to the external surface through the taste pore, an opening in the taste bud. Sites of taste transduction.
20
Q
Basal cells (of the taste buds)
A
Stem cells that are found at the periphery of the taste bud near the connective tissue layer. Produce supporting cells, which then develop into gustatory receptor cells.
21
Q
Papillae
A
AKA papilla; elevations of the tongue where taste buds are found. Increase the surface area and provide a rough texture to the upper surface of the tongue.
22
Q
What are the three types of papillae that contain taste buds?
A
- Vallate papillae
- Fungiform papillae
- Foliate papillae
23
Q
Vallate papillae
A
AKA circumvallate papillae; about 12 very large, circular elevations that form an inverted V-shaped row at the back of the tongue. Each of these papillae houses 100–300 taste buds.
24
Q
Fungiform papillae
A
Mushroom-shaped elevations scattered over the entire surface of the tongue that contain about five taste buds each.
25
Foliate papillae
Are located in small trenches on the lateral margins of the tongue, but most of their taste buds degenerate in early childhood.
26
Filiform papillae
Pointed, threadlike structures that contain tactile receptors but no taste buds. They increase friction between the tongue and food, making it easier for the tongue to move food in the oral cavity. Are found on the entire surface of the tongue.
27
Tastants
Chemicals that stimulate gustatory receptor cells.
28
The receptor potential arises ______ for different tastants.
Differently
29
The ______ ions in a salty food enter gustatory receptor cells via __ channels in the plasma membrane. The accumulation of __ inside the cell causes ______, which leads to release of neurotransmitter. The hydrogen ions (H+) in sour tastants flow into gustatory receptor cells via H+ channels. Again, the result is depolarization and the liberation of neurotransmitter. Other tastants, responsible for stimulating sweet, bitter, and umami tastes, do not themselves enter gustatory receptor cells. Rather, they bind to receptors on the plasma membrane that are linked to G proteins. The G proteins then activate enzymes that produce the second messenger inositol trisphosphate (IP3). IP3 in turn ultimately causes depolarization of the gustatory receptor cell and release of neurotransmitter.
Sodium; Na+; Na+; depolarization
30
Why is vision important?
Vision is extremely important to human survival because it allows us to view potentially dangerous objects in our surroundings. More than half the sensory receptors in the human body are located in the eyes, and a large part of the cerebral cortex is devoted to processing visual information.
31
Visible light
The part of the electromagnetic spectrum with wavelengths ranging from about 400 to 700 nm. Visible light exhibits colors: The color of visible light depends on its wavelength (Eg. Light that has a wavelength of 400 nm is violet, and light that has a wavelength of 700 nm is red). An object can absorb certain wavelengths of visible light and reflect others; the object will appear the color of the wavelength that is reflected (Eg. A green apple appears green because it reflects mostly green light and absorbs most other wavelengths of visible light). An object appears white because it reflects all wavelengths of visible light. An object appears black because it absorbs all wavelengths of visible light.
32
What are the five accessory structures of the eye?
1. Eyelids
2. Eyelashes
3. Eyebrows
4. Lacrimal (tear-producing) apparatus
5. Extrinsic eye muscles
33
Eyelids
AKA palpebrae (or palpebra); shade the eyes during sleep, protect the eyes from excessive light and foreign objects, and spread lubricating secretions over the eyeballs. The upper eyelid is more movable than the lower eyelid.
34
Levator palpebrae superioris muscle
In the superior region of the upper eyelid.
35
Palpebral fissure
The space between the upper and lower eyelids that exposes the eyeball.
36
Lateral commissure
Angles of the palpebral fissure. Narrower and closer to the temporal bone.
37
Medial commissure
Angles of the palpebral fissure. Broader and nearer the nasal bone.
38
Lacrimal caruncle
A small, reddish elevation in the medial commissure. Contains sebaceous (oil) glands and sudoriferous (sweat) glands.
39
From superficial to deep, what seven things does each eyelid consist of?
1. Epidermis
2. Dermis
3. Subcutaneous tissue
4. Fibers of the orbicularis oculi muscle
5. Tarsal plate
6. Tarsal glands
7. Conjunctiva
40
Tarsal plate
A thick fold of connective tissue that gives form and support to the eyelids.
41
Tarsal glands
AKA Meibomian glands; a row of elongated modified sebaceous glands embedded in each tarsal plate. Secrete a fluid that helps keep the eyelids from adhering to each other.
42
Conjunctiva
A thin, protective mucous membrane composed of nonkeratinized stratified squamous epithelium with numerous goblet cells that is supported by areolar connective tissue.
43
Palpebral conjunctiva
Lines the inner aspect of the eyelids.
44
Bulbar conjunctiva
Passes from the eyelids onto the surface of the eyeball, where it covers the sclera but not the cornea. Over the sclera, the conjunctiva is vascular. Dilation and congestion of the blood vessels of the bulbar conjunctiva due to local irritation or infection are the cause of bloodshot eyes.
45
Eyelashes
Project from the border of each eyelid.
46
Eyebrows
Arch transversely above the upper eyelids, and help protect the eyeballs from foreign objects, perspiration, and the direct rays of the sun.
47
Sebaceous ciliary glands
Sebaceous glands at the base of the hair follicles of the eyelashes. Release lubricating fluid into the follicles. Infection of these glands, usually by bacteria, causes a sty.
48
Lacrimal apparatus
Is a group of structures that produces and drains lacrimal fluid or tears in a process called lacrimation.
49
______ secrete tears into the ______, which distribute tears over surface of the eyeball. ______ drain tears into the ______, which drains tears into the ______, which drains tears into the nasal cavity.
Lacriminal glands; excretory lacrimal ducts; superior or inferior lacrimal canaliculi; lacrimal sac; nosalacriminal duct
50
Lacrimal puncta
Two small openings.
51
Lacrimal fluid
Produced by lacrimal glands. Is a watery solution containing salts, some mucus, and lysozyme (a protective bactericidal enzyme). This fluid protects, cleans, lubricates, and moistens the eyeball. Spread medially over the surface of the eyeball by the blinking of the eyelids. Each gland produces about 1mL of lacrimal fluid per day.
52
Extrinsic eye muscles
Extend from the walls of the bony orbit to the sclera of the eye and are surrounded in the orbit by a significant quantity of periorbital fat. These muscles are capable of moving the eye in almost any direction.
53
__ extrinsic eye muscles move each eye.
6
54
Eyeball
Measures about 2.5 cm (1 in.) in diameter. Anterior one-sixth is exposed – the remainder is recessed and protected by the orbit, into which it fits.
55
What three layers does the wall of the eyeball consist of?
1. Fibrous tunic
2. Vascular tunic
3. Retina (inner tunic)
56
Fibrous tunic
The superficial layer of the eyeball.
57
What two structures does the fibrous tunic consist of?
1. Cornea
2. Sclera
58
Cornea
Admits and refracts (bends) light.
59
Sclera
Provides shape and protects inner parts.
60
Scleral venous sinus
AKA canal of Schlemm; an opening at the junction of the sclera and cornea, which aquous humor drains into.
61
Vascular tunic
AKA uvea; the middle layer of the eyeball.
62
What three structures does the vascular tunic consist of?
1. Choroid
2. Ciliary body
3. Iris
63
Choroid
Provides blood supply and absorbs scattered light.
64
Ciliary body
Secretes aqueous humour and alters shape of lens for near or far vision (accommodation).
65
Ora serrata
The jagged anterior margin of the retina.
66
Ciliary processes
Protrusions or folds on the internal surface of the ciliary body. They contain blood capillaries that secrete aqueous humor.
67
Zonular fibers
AKA suspensory ligaments; extend from the ciliary process and attach to the lens. Consist of thin, hollow fibrils that resemble elastic connective tissue fibers.
68
Ciliary muscle
A circular band of smooth muscle. Contraction or relaxation of the ciliary muscle changes the tightness of the zonular fibers, which alters the shape of the lens, adapting it for near or far vision.
69
Iris
Regulates amount of light that enters eyeball.
70
Pupil
The hole in the center of the iris. Regulates the amount of light entering the eyeball.
71
Circular muscles
AKA sphincter pupillae; contract to decrease the size of the pupil (constrict the pupil).
72
Radial muscles
AKA dilator muscles: contract to increase the size of the pupil (dilate the pupil).
73
Retina (inner tunic)
Receives light and converts it into receptor potentials and nerve impulses. Output to brain via axons of ganglion cells, which form optic (II) nerve.
74
Optic disc
Site where the optic (II) nerve exits the eyeball.
75
Central retinal artery
Nourishes the anterior surface of the retina.
76
Central retinal vein
Drains blood from the retina through the optic disc.
77
Pigmented layer (of the retina)
A sheet of melanin-containing epithelial cells located between the choroid and the neural part of the retina. The melanin in this layer helps to absorb stray light rays.
78
Neural (sensory) layer (of the retina)
A multilayered outgrowth of the brain that processes visual data extensively before sending nerve impulses into axons that form the optic nerve.
79
Three distinct layers of retinal neurons – the ______ layer, the ______ layer, and the ______ layer – are separated by two zones, the ______ and ______ layers, where synaptic contacts are made. Note that light passes through the ganglion and bipolar cell layers and both synaptic layers before it reaches the photoreceptor layer. Two other types of cells present in the bipolar cell layer of the retina are called ______ and ______. These cells form laterally directed neural circuits that modify the signals being transmitted along the pathway from photoreceptors to bipolar cells to ganglion cells.
Photoreceptor cell; bipolar cell; ganglion cell; outer synaptic; inner synaptic; horizontal cells; amacrine cells
80
Rods
A type of photoreceptor; allow us to see in dim light, such as moonlight. Do not provide color vision.
81
Cones
A type of photoreceptor; allow us to see bright light. Produce color vision.
82
What are the three types fo cones in the retina? What are they sensitive to?
1. Blue cones: sensitive to blue light.
2. Green cones: sensitive to green light.
3. Red cones: sensitive to red light.
83
Blind spot
Another name for the optic disc because it it contains no rods or cones so we cannot see images that strike the blind spot.
84
Macula lutea
AKA yellow spot; is in the exact center of the posterior portion of the retina, at the visual axis of the eye.
85
Fovea centralis
A small depression in the center of the macula lutea that contains only cones. Is the area of highest visual acuity or resolution (sharpness of vision).
86
Lens
Refracts light
87
Crystallins
Proteins within the cells of the lens that are arranged like the layers of an onion. Make up the refractive media of the lens, which normally is perfectly transparent and lacks blood vessels. It is enclosed by a clear connective tissue capsule and held in position by encircling zonular fibers, which attach to the ciliary processes.
88
Anterior cavity (of the lens)
Contains aqueous humor that helps maintain shape of the eyeball and supplies oxygen and nutrients to lens and cornea.
89
What two chambers does the anterior cavity consist of?
1. Anterior chamber
2. Posterior chamber
90
Anterior chamber
Lies between the cornea and the iris. Filled with aqueous humor.
91
Posterior chamber
Lies behind the iris and in front of the zonular fibers and lens. Filled with aqueous humor.
92
Aqueous humor
A transparent watery fluid that nourishes the lens and cornea. Replaced about every 90 minutes.
93
Vitreous chamber
Contains vitreous body that helps maintain shape of eyeball and keeps retina attached to choroid.
94
Hyaloid canal
A narrow channel that is inconspicuous in adults and runs through the vitreous body from the optic disc to the posterior aspect of the lens. In the fetus, it is occupied by the hyaloid artery.
95
Intraocular pressure
The pressure in the eye; is produced mainly by the aqueous humor and partly by the vitreous body; normally it is about 16 mmHg (millimeters of mercury). It maintains the shape of the eyeball and prevents it from collapsing.
96
What are the three important processes for understanding how the eye forms clear images of objects on the retina?
1. The refraction or bending of light by the lens and cornea.
2. Accommodation, the change in shape of the lens.
3. Constriction or narrowing of the pupil.
97
Refraction
The bending of light rays at the junction of two transparent substances with different densities.
98
Convex
A surface that curves outward, like the surface of a ball. When the surface of a lens is convex, that lens will refract incoming light rays toward each other, so that they eventually intersect.
99
Concave
A surface that curves inward, like the inside of a hollow ball. When the surface of a lens is concave, that lens will refract incoming light away from eachother.
100
Accommodation
Increase in the curvature of the lens for near vision. Parasympathetic fibers of the oculomotor (III) nerve mediate the process of accommodation.
101
Near point of vision
The minimum distance from the eye that an object can be clearly focused with maximum accommodation. This distance is about 10 cm (4 in.) in a young adult.
102
Emmetropic eye
The normal eye. Can sufficiently refract light rays from an object 6 m (20 ft) away so that a clear image is focused on the retina.
103
Myopia
AKA nearsightedness; occurs when the eyeball is too long relative to the focusing power of the cornea and lens, or when the lens is thicker than normal, so an image converges in front of the retina. Myopic individuals can see close objects clearly, but not distant objects.
104
Hyperopia
AKA farsightedness or hypermetropia: the eyeball length is short relative to the focusing power of the cornea and lens, or the lens is thinner than normal, so an image converges behind the retina. Hyperopic individuals can see distant objects clearly, but not close ones.
105
Astigmatism
Either the cornea or the lens has an irregular curvature. As a result, parts of the image are out of focus, and thus vision is blurred or distorted.
106
Binocular vision
Characteristic in humans in which both eyes focus on only one set of objects.
107
Convergence
The medial movement of the two eyeballs so that both are directed toward the object being viewed (Eg. Tracking a pencil moving toward your eyes). The nearer the object, the greater the degree of convergence needed to maintain binocular vision. The coordinated action of the extrinsic eye muscles brings about convergence.
108
Outer segment (of photoreceptors)
The distal end next to the pigmented layer. Where transduction of light energy into a receptor potential occurs.
109
Inner segment (of photoreceptors)
Contains the cell nucleus, golgi complex, and many mitochondria.
110
Photopigment
AKA visual pigment; a colored protein that undergoes structural changes when it absorbs light, in the outer segment of a photoreceptor.
111
Cone photopigments
Three present in the retina - one in each of the three types of cones (blue, green, and red cones). Color vision results from different colors of light selectively activating the different cone photopigments.
112
What two parts do all photopigments associated with vision contain?
1. Opsin (a glycoprotein)
2. Retinal (a vitamin A derivative; the light-absorbing part of all visual photopigments)
113
What are the four steps of the cyclical process of photopigments responding to light? Describe these four steps
1. Isomerization: in darkness, retinal has a bent shape, which is called cis-retinal. This cis-retinal fits into the opsin portion of the photopigment. When cis-retinal absorbs a photon of light, it straightens out to a shape called trans-retinal. Isomerization is the cis-to-trans conversion.
2. Bleaching: trans-retinal separating from opsin. Retinal is responsible for the color of the photopigment, so the separation of trans-retinal from opsin causes opsin to look colorless.
3. Conversion: an enzyme called retinal isomerase converts trans-retinal back to cis-retinal.
4. Regeneration: Cis-retinal binds to opsin to reform a functional photopigment.
114
Light adaptation
Emerging from dark to light surroundings. The visual system adjusts to the brighter environment by decreasing its sensitivity.
115
Dark adaptation
Emerging from light to dark surroundings. The visual system adjusts to the darker environment by increasing its sensitivity.
116
Phototransduction
The process by which light energy is converted into a receptor potential in the outer segment of a photoreceptor. Activation of a photoreceptor by its adequate stimulus (light) causes a hyperpolarizing receptor potential.
117
Hearing
The ability to perceive sounds.
118
What three main regions are involved in hearing?
1. External (outer) ear
2. Middle ear
3. Internal (inner) ear
119
External (outer) ear
Collects sound waves and channels them inwards.
120
What are the three structures of the external (outer) ear?
1. Auricle
2. External auditory canal
3. Tympanic membrane (eardrum)
121
Auricle
AKA pinna; collects sound waves.
122
Helix
Rim of the auricle.
123
Lobule
Inferior portion of the auricle.
124
External auditory canal
Directs sound waves to eardrum.
125
Tympanic membrane
AKA eardrum; sound waves cause it to vibrate, which in turn causes the malleus to vibrate.
126
Ceruminous glands
Specialized sweat glands near the exterior opening of the external auditory canal. Secrete earwax or cerumen.
127
Earwax
AKA cerumen; helps prevent dust and foreign objects from entering the ear. Also prevents damage to the delicate skin of the external ear canal by water and insects.
128
Middle ear
Conveys sound vibrations to the oval window.
129
What are the two structures of the middle ear?
1. Auditory ossicles
2. Auditory tube
130
Auditory ossicles
Transmit and amplify vibrations from tympanic membrane to oval window.
131
What are the three auditory ossicles?
1. Malleus
2. Incus
3. Stapes
132
Oval window
What the stapes fits into.
133
Round window
An opening directly below the oval window.
134
Secondary tympanic membrane
A membrane that encloses the round window.
135
Tensor tympani
Tiny skeletal muscle attached to the ossicles. Is supplied by the mandibular branch of the trigeminal (V) nerve and acts to limit movement and increase tension on the eardrum to prevent damage to the inner ear from loud noises.
136
Stapedius
Tiny skeletal muscle attached to the ossicles. Is the smallest skeletal muscle in the human body. Is supplied by the facial (VII) nerve and acts to protect the oval window and decrease sensitivity of hearing.
137
Auditory tube
AKA pharyngotympanic tube or the eustachian tube; equalizes air pressure on both sides of the tympanic membrane.
138
Internal (inner) ear
Houses the receptors for hearing and equilibrium.
139
What are the two main divisions of the internal (inner) ear?
1. Bony labyrinth
2. Membranous labyrinth
140
Bony labyrinth
A series of cavities in the petrous portion of the temporal bone. Contains perilymph.
141
What are the three areas that the bony labyrinth can be divided into?
1. Semicircular canals
2. Vestibule
3. Cochlea
142
Semicircular canals
Three of them. Each lies at approximately right angles to the other two. Based on their positions, they are named the anterior, posterior, and lateral semicircular canals. The anterior and posterior semicircular canals are vertically oriented; the lateral one is horizontally oriented.
143
Ampulla
Swollen enlargement at one end of each semicircular canal.
144
Semicircular ducts
Detect rotational acceleration and deceleration.
145
The vestibular branch of the vestibulocochlear (VIII) nerve consists of ______, ______, and ______ nerves.
Ampullary; utricular; saccular
146
Vestibule
The oval central portion of the bony labyrinth.
147
Cochlea
Contain a series of fluids, channels, and membranes that transmit vibrations to spiral organ (organ of Corti), the organ of hearing; hair cells in spiral organ produce receptor potentials, which elicit nerve impulses in cochlear branch of vestibulocochlear (VIII) nerve
148
Cochlear duct
Is a continuation of the membranous labyrinth into the cochlea. Filled with endolymph.
149
Scala vestibuli
Channel above the cochlear duct that ends at the oval window. Filled with perilymph.
150
Scala tympani
Channel below the cochlear duct that ends at the round window. Filled with perilymph.
151
Modiolus
Central bony core of cochlea.
152
Helicotrema
Where the scala vestibuli and scala tympani's perilymph mixes.
153
Perilymph
Fluid within the bony labyrinth.
154
Vestibular membrane
Separates the cochlear duct from the scala vestibuli.
155
Basilar membrane
Separates the cochlear duct from the scala tympani.
156
Spiral organ (organ of Corti)
Rests on the basilar membrane. Is a coiled sheet of epithelial cells, including supporting cells and hair cells.
157
Hair cells
The receptors for hearing. Contain stereocilia and one kinocilium.
158
What are the two groups of hair cells? Describe them
1. Inner hair cells: they convert the mechanical vibrations of sound into electrical signals.
2. Outer hair cells: they increase the sensitivity of the inner hair cells.
159
Spiral ganglion
Where cell bodies of sensory neurons are located.
159
Stereocilia
At the apical tip of each hair cell. Extend into the endolymph of the cochlear duct.
160
Tectorial membrane
A flexible gelatinous membrane that covers the hair cells of the spiral organ. The ends of the stereocilia of the hair cells are embedded in the tectorial membrane while the bodies of the hair cells rest on the basilar membrane.
161
Membranous labyrinth
A series of epithelial sacs and tubes inside the bony labyrinth that have the same general form as the bony labyrinth and house the receptors for hearing and equilibrium. Contains endolymph.
162
Endolymph
Fluid within the membranous labyrinth. Contains high levels of potassium ions (K+).
163
Sound waves
Alternating high- and low-pressure regions traveling in the same direction through some medium (such as air).
164
The frequency of a sound vibration is its ______. The higher the frequency of vibration, the ______ is ______.
Pitch; higher; pitch
165
The larger the intensity (size or amplitude) of the vibration, the ______ is the sound.
Louder
166
What are the eight steps involved in hearing?
1. The auricle directs sound waves into the external auditory canal.
2. When sound waves strike the tympanic membrane, the alternating waves of high and low pressure in the air cause the tympanic membrane to vibrate back and forth. The tympanic membrane vibrates slowly in response to low-frequency (low-pitched) sounds and rapidly in response to high-frequency (high-pitched) sounds.
3. The central area of the tympanic membrane connects to the malleus, which vibrates along with the tympanic membrane. This vibration is transmitted from the malleus to the incus and then to the stapes.
4. As the stapes moves back and forth, its oval-shaped footplate, which is attached via a ligament to the circumference of the oval window, vibrates in the oval window. The vibrations at the oval window are about 20 times more vigorous than those of the tympanic membrane because the auditory ossicles efficiently transmit small vibrations spread over a large surface area (the tympanic membrane) into larger vibrations at a smaller surface (the oval window).
5. The movement of the stapes at the oval window sets up fluid pressure waves in the perilymph of the cochlea. As the oval window bulges inward, it pushes on the perilymph of the scala vestibuli.
6. Pressure waves are transmitted from the scala vestibuli to the scala tympani and eventually to the round window, causing it to bulge outward into the middle ear.
7. As the pressure waves deform the walls of the scalea vestibuli and scala tympani, they also push the vestibular membrane back and forth, creating pressure waves in the endolymph inside the cochlear duct.
8. The pressure waves in the endolymph cause the basilar membrane to vibrate, which moves the hair cells of the spiral organ against the tectorial membrane. This leads to bending of the stereocilia and ultimately to the generation of nerve impulses in first-order neurons in cochlear nerve fibers.
167
Sound waves of various frequencies cause certain regions of the basilar membrane to vibrate more intensely than other regions. Each segment of the basilar membrane is “tuned” for a particular pitch. Because the membrane is narrower and stiffer at the base of the cochlea (closer to the oval window), ______-frequency sounds induce maximal vibrations in this region. Toward the apex of the cochlea, the basilar membrane is wider and more flexible; ______-frequency sounds cause maximal vibration of the basilar membrane there.
High; low
168
Equilibrium
AKA balance; changes in equilibrium can be detected by the ears. Body movements that stimulate the receptors for equilibrium include linear acceleration or deceleration, tilting the head forward or backward, and rotational (angular) acceleration or deceleration.
169
Vestibular apparatus
Include semicircular ducts, utricle, and saccule, which generate nerve impulses that propagate along the vestibular branch of vestibulocochlear (VIII) nerve.
170
Otolithic organs
Include the utricle and saccule.
171
Utricle
Detects linear acceleration or deceleration that occurs in a horizontal direction and also head tilt.
172
Saccule
Detects linear acceleration or deceleration that occurs in a vertical direction.
173
Macula
A small, thickened region that is attached to the inner walls of both the utricle and saccule.
174
What two types of cells does that macula consist of?
1. Hair cells
2. Supporting cells
175
Hair bundle
What the stereocilia and kinocilium are collectively called.
176
Otolithic membrane
Thick, gelatinous, glycoprotein layer that rests on the hair cells.
177
Otoliths
Layer of dense calcium carbonate crystals that extends over the entire surface of the otolithic membrane.
178
Crista
Small elevation. Consists of a group of hair cells and supporting cells.
179
Cupula
A mass of gelatinous material that covers the crista.
