CHAPTER 15 SPECIAL SENSES Flashcards
1
Q
1) Where are the general senses located? A) skin B) nose C) eyes D) tongue
A
A) skin
2
Q
2) What nerves carry information about the special senses to the CNS? A) cranial nerves only
B) spinal nerves only
C) cervical nerves only
D) both cranial and spinal nerves
A
A) cranial nerves only
3
Q
3) To what part of the brain are both general and most special senses carried? A) pons B) medulla oblongata C) thalamus D) hypothalamus
A
C) thalamus
4
Q
4) Special senses, such as sight and sound, are converted to an action potential by: A) sensation. B) interpretation. C) transduction. D) perception.
A
C) transduction.
5
Q
5) Olfaction is the sense of: A) taste. B) smell. C) balance. D) hearing.
A
B) smell.
6
Q
6) The olfactory nerves (CN I) are formed by: A) supporting cells. B) olfactory bulbs. C) olfactory tracts. D) axons of the olfactory neurons.
A
D) axons of the olfactory neurons.
7
Q
7) Damage to the basal cells in the olfactory epithelium results in a loss of: A) hearing. B) vision. C) taste. D) smell.
A
D) smell.
8
Q
8) The activation of olfactory receptors requires that the odorant become immersed in: A) mucus. B) blood. C) cerumen. D) saliva.
A
A) mucus.
9
Q
9) Place the following steps in the correct order for transduction of a chemical odorant into a nerve signal.
1. Odorants reach receptors in the cilia of olfactory neurons.
2. cAMP opens ions channels that allow sodium and calcium ions to enter the cell.
3. The G-protein activates an enzyme, adenylate cyclase, to convert ATP into cyclic AMP (cAMP).
4. The binding of an odorant activates a G-protein which then detaches from the receptor. 5. The membrane is depolarized. Depolarization that reaches threshold at the axon hillock triggers an action potential and transduction has been achieved.
A) 1, 4, 3, 2, 5
B) 1, 2, 3, 4, 5
C) 1, 3, 4, 2, 5
D) 1, 4, 2, 3, 5
A
A) 1, 4, 3, 2, 5
10
Q
10) Place the following steps of nerve impulses in the olfaction pathway in order. 1. primary olfactory cortex in the temporal lobe
2. olfactory nerve
3. olfactory neurons
4. olfactory bulb
A) 3, 2, 4, 1
B) 2, 3, 4, 1
C) 3, 4, 2, 1
D) 2, 4, 3, 1
A
A) 3, 2, 4, 1
11
Q
11) Which of the following papillae found on the surface of the tongue contains no taste buds, but does contain sensory nerve endings to detect the temperature and texture of food? A) filiform papillae B) foliate papillae C) fungiform papillae D) vallate (circumvallate) papillae
A
A) filiform papillae
12
Q
REFER TO PICTURE OF THE TONGUE
12) Which letter represents the foliate taste buds?
A) A
B) B
C) C
A
B) B
13
Q
13) Which cell has receptors specialized to detect different tastes? A) olfactory cell
B) supporting cell
C) basal cell
D) gustatory cell
A
D) gustatory cell
14
Q
14) Taste is detected when chemicals bind receptors on the microvilli of: A) basal cells. B) supporting cells. C) gustatory cells. D) olfactory cells.
A
C) gustatory cells.
15
Q
15) How is the sensation of taste affected by a dry mouth?
A) Foods have a more intense taste when the mouth is dry.
B) Foods have a less intense taste when the mouth is dry.
C) The moisture level of the mouth has no influence on taste sensation. D) Most foods will taste bitter when the mouth is dry.
A
B) Foods have a less intense taste when the mouth is dry.
16
Q
16) What taste sensation results when sodium ions enter gustatory cells through sodium ion channel receptors, and the cell depolarizes? A) bitter B) sour C) umami D) salty
A
D) salty
17
Q
17) Aiden was surprised to learn that his salad dressing contained glucose since it did NOT taste: A) salty. B) sweet. C) bitter. D) sour.
A
B) sweet.
18
Q
18) Identify the cranial nerves NOT involved in carrying taste information from the tongue into the CNS. A) hypoglossal nerves (CN XII) B) vagus nerves (CN X) C) facial nerves (CN VII) D) glossopharyngeal nerves (CN IX)
A
A) hypoglossal nerves (CN XII)
19
Q
19) Damage to the facial nerve would result in a loss of taste sensation from: A) roof of the mouth. B) posterior one-third of the tongue. C) anterior two-thirds of the tongue. D) base of the tongue.
A
C) anterior two-thirds of the tongue.
20
Q
20) Where is the primary gustatory cortex located? A) occipital lobe B) parietal lobe C) temporal lobe D) frontal lobe
A
B) parietal lobe
21
Q
21) What gland secretes oil to prevent the eyelids from sticking together? A) lacrimal gland B) sudoriferous gland C) tarsal gland D) ceruminous gland
A
C) tarsal gland
22
Q
REFER TO PICTURE OF THE EYE
22) Select the letter representing the nasolacrimal duct. A) A B) B C) C D) D
A
D) D
23
Q
23) A weak superior oblique muscle would impair:
A) depression of the eye and lateral movement.
B) superior movement of the eye.
C) lateral movement and elevation of the eye.
D) inferior and lateral movement of the eye.
A
A) depression of the eye and lateral movement.
24
Q
24) Which extrinsic eye muscles act together to move the eye directly inferiorly? A) superior oblique and inferior rectus B) lateral rectus and inferior oblique C) inferior oblique and superior rectus D) inferior oblique and inferior rectus
A
A) superior oblique and inferior rectus
25
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25) The three layers of the eyeball, from outer to inner, are:
A) vascular, neural, and fibrous layers.
B) fibrous, neural, and vascular layers.
C) neural, vascular, and fibrous layers.
D) fibrous, vascular, and neural layers.
```
D) fibrous, vascular, and neural layers.
26
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26) The sclera is continuous with a transparent layer over the anterior eye known as the:
A) lens.
B) cornea.
C) conjunctiva.
D) choroid.
```
B) cornea.
27
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27) What part of the eye controls the amount of light entering through the pupil?
A) cornea
B) sclera
C) iris
D) lens
```
C) iris
28
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28) What region of the retina contains a high density of photoreceptor cells and allows for extremely detailed vision?
A) optic disc
B) fovea centralis
C) ciliary body
D) ora serrata
```
B) fovea centralis
29
29) The optic disc is known as the blind spot because:
A) only cones populate the optic disc.
B) photoreceptors are absent from the optic disc.
C) the fovea centralis prevents light from striking the optic disc.
D) only rods populate the optic disc.
B) photoreceptors are absent from the optic disc.
30
30) What is the function of the lens?
A) The lens focuses light on the retina.
B) The lens nourishes the retina.
C) The lens controls the amount of light passing through the pupil.
D) The lens reduces the scattering of light.
A) The lens focuses light on the retina.
31
```
31) What secretes the aqueous humor?
A) vitreous humor
B) ciliary body
C) iris
D) lens
```
B) ciliary body
32
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32) What gelatinous mass helps maintain the shape of the eyeball?
A) perilymph
B) aqueous humor
C) ora serrata
D) vitreous humor
```
D) vitreous humor
33
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33) What unit of light stimulates photoreceptor cells in the retina?
A) refractive index
B) gamma ray
C) photon
D) glutamate
```
C) photon
34
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34) Which of the following parts of the eye refract light to focus it on the retina?
A) ciliary body and suspensory ligaments
B) pupil and iris
C) cornea and lens
D) sclera and choroid
```
C) cornea and lens
35
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35) The ability of the lens to change its shape from flattened to round is known as:
A) accommodation.
B) inversion.
C) refraction.
D) convergence.
```
A) accommodation.
36
36) Twenty-year-old Leslie learned she is hyperopic after having her eyes examined. What best describes her eye condition?
A) Her eyeballs are too short.
B) Her eyeballs are too long.
C) Her eyeball shape is normal.
D) Her eyes are experiencing age-related decline.
A) Her eyeballs are too short.
37
37) Determine the correct order of events that occur when light strikes photoreceptor cells.
1. The bipolar cell depolarizes.
2. Action potentials are sent to the brain via the optic nerve (CN II).
3. Light hyperpolarizes the photoreceptor.
4. Retinal ganglion cell produces action potentials.
A) 3, 4, 1, 2
B) 3, 1, 4, 2
C) 1, 4, 2, 3
D) 3, 2, 4, 1
B) 3, 1, 4, 2
38
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38) What type of photoreceptor cell perceives color?
A) bipolar cell
B) rod
C) cone
D) hair cell
```
C) cone
39
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39) What pigment is derived from vitamin A?
A) photopsin
B) retinal
C) opsin
D) transducin
```
B) retinal
40
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40) The three types of cones are designated:
A) yellow, red, and blue.
B) red, yellow, and blue.
C) red, green, and yellow.
D) red, green, and blue.
```
D) red, green, and blue.
41
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41) People who are unable to distinguish certain colors have a form of:
A) color blindness.
B) glaucoma.
C) cataracts.
D) astigmatism.
```
A) color blindness.
42
42) When a photoreceptor cell is stimulated by light:
A) sodium ions enter the outer segment of the photoreceptor and depolarize it.
B) transducin and phosphodiesterase (PDE) are inactive.
C) the photoreceptor hyperpolarizes as sodium ion channels close.
D) opsin and cis-retinal combine to form rhodopsin.
C) the photoreceptor hyperpolarizes as sodium ion channels close.
43
43) In the light-adapted state:
A) rods are bleached and unable to function.
B) colors are dull.
C) we can only see color and not black and white.
D) we could see better in the dark.
A) rods are bleached and unable to function.
44
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44) In the dark (absence of a stimulus), the photoreceptors are:
A) depolarized.
B) bleached.
C) polarized.
D) hyperpolarized.
```
A) depolarized.
45
45) Having to adjust to a dark room after walking in from bright light is because:
A) rods exposed to bright light need time to regenerate rhodopsin.
B) the lens requires time to accommodate dim light.
C) rhodopsin does not function in dim light.
D) only cones function in dim light.
A) rods exposed to bright light need time to regenerate rhodopsin.
46
```
46) Where does each half of the visual field get segregated so that it reaches the opposite hemisphere of the brain?
A) lateral geniculate nucleus
B) hypothalamus
C) optic chiasma
D) occipital lobe
```
C) optic chiasma
47
47) The inability to recognize a family member indicates impairment in the: A) parietal lobe.
B) dorsal pathway.
C) anterior (ventral) pathway.
D) pretectal area.
C) anterior (ventral) pathway.
48
48) What is NOT a function of cerumen?
A) Cerumen waterproofs and lubricates the external auditory canal.
B) Cerumen traps debris before it reaches the tympanic membrane.
C) Cerumen enhances sound transmission into the ear canal.
D) Cerumen sweeps debris from the external auditory canal.
C) Cerumen enhances sound transmission into the ear canal.
49
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49) What separates the outer ear from the middle ear?
A) pharyngotympanic tube
B) auricle
C) tympanic membrane
D) auditory ossicles
```
C) tympanic membrane
50
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50) Which auditory ossicle is connected to the tympanic membrane?
A) incus
B) malleus
C) stapes
D) anvil
```
B) malleus
51
51) What equalizes pressure on both sides of the tympanic membrane?
A) round window
B) pharyngotympanic tube (auditory tube)
C) external auditory canal (external acoustic meatus)
D) oval window
B) pharyngotympanic tube (auditory tube)
52
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52) What creates the boundary between the air-filled middle ear and the fluid-filled inner ear?
A) oval window
B) basilar membrane
C) tympanic membrane
D) tectorial membrane
```
A) oval window
53
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53) If the stapedius muscle is unable to reduce movement of the ossicles as a unit, how is hearing affected?
A) We hear no sound.
B) Sounds will be softer than normal.
C) Sounds will be louder than normal.
D) Hearing is not affected.
```
C) Sounds will be louder than normal.
54
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54) The vibrations received by the tympanic membrane are transferred to the oval window by the:
A) auditory ossicles.
B) oval window.
C) cochlea.
D) stapedius muscle.
```
A) auditory ossicles.
55
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55) Which part of the inner ear houses two portions of the membranous labyrinth known as the utricle and saccule?
A) cochlea
B) semicircular canals
C) vestibule
D) tympanic membrane
```
B) semicircular canals
56
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56) What part of the inner ear is involved in hearing?
A) utricle
B) cochlea
C) vestibule
D) saccule
```
B) cochlea
57
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57) What cranial nerve carries information about hearing and head movement to the brain?
A) abducens nerve (CN VI)
B) trigeminal nerve (CN IV)
C) trochlear nerve (CN V)
D) vestibulocochlear nerve (CN VIII)
```
D) vestibulocochlear nerve (CN VIII)
58
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58) A person who has a cochlear implant needs this device for:
A) balance.
B) hearing.
C) the prevention of nausea.
D) the prevention of dizziness.
```
B) hearing.
59
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59) Standing still in an elevator that suddenly lowers stimulates receptors in the:
A) basilar membrane.
B) spiral organ (organ of Corti).
C) bony labyrinth.
D) utricle and saccule.
```
D) utricle and saccule.
60
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60) What supports the spiral organ (organ of Corti)?
A) tectorial membrane
B) basilar membrane
C) membranous labyrinth
D) tympanic membrane
```
B) basilar membrane
61
61) As sound waves travel into the ear, they pass from the auditory canal to the:
A) tympanic membrane, auditory ossicles, oval window, perilymph, scala vestibuli of the cochlea.
B) tympanic membrane, auditory ossicles, round window, perilymph, scala vestibuli of the cochlea.
C) tympanic membrane, oval window, auditory ossicles, perilymph, scala vestibuli of the cochlea.
D) tympanic membrane, auditory ossicles, oval window, endolymph, scala vestibuli of the cochlea.
A) tympanic membrane, auditory ossicles, oval window, perilymph, scala vestibuli of the cochlea.
62
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62) Where are sound vibrations amplified?
A) semicircular canals
B) tympanic membrane
C) auditory ossicles
D) vestibule
```
C) auditory ossicles
63
63) The loudness of sound is determined by the vibrations of the: A) scala vestibuli.
B) otoliths.
C) basilar membrane.
D) tectorial membrane.
C) basilar membrane.
64
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64) Damage to the hair cells of the spiral organ (organ of Corti) can result in a loss of:
A) hearing.
B) vision.
C) equilibrium.
D) olfaction.
```
A) hearing.
65
65) When sound waves bend stereocilia, what happens?
A) Hearing loss results.
B) Hair cells hyperpolarize as potassium flows into the cell through open channels.
C) Hair cells depolarize, releasing neurotransmitter, and triggering an action potential.
D) The force of the sound waves is converted into mechanical energy.
C) Hair cells depolarize, releasing neurotransmitter, and triggering an action potential.
66
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66) The startle reflex occurs when unexpected sounds reach the:
A) thalamus.
B) midbrain.
C) hypothalamus.
D) pons.
```
B) midbrain.
67
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67) Where does the conscious awareness of sound begin, along with the analysis of its pitch, location, and loudness?
A) frontal lobe
B) parietal lobe
C) occipital lobe
D) temporal lobe
```
D) temporal lobe
68
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68) The sense of equilibrium does NOT depend on input from:
A) the cochlea.
B) proprioceptors in muscles and joints.
C) the vestibular system.
D) the visual system.
```
A) the cochlea.
69
69) Which of the following is an example of static equilibrium?
A) spinning on a merry-go-round at the park
B) riding in an elevator
C) sitting in a movie theater to watch a film
D) riding in a car
C) sitting in a movie theater to watch a film
70
70) The receptor cells for static equilibrium are located in the:
A) otolithic membrane of the utricle and saccule of the vestibule.
B) spiral organ (organ of Corti) of the cochlea.
C) ampullae of the semicircular canals.
D) maculae of the utricle and saccule of the vestibule.
D) maculae of the utricle and saccule of the vestibule.
71
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71) The otolithic membrane plays a role in the detection of:
A) linear acceleration and head tilting.
B) rotational head movements.
C) hearing.
D) startle reflex.
```
A) linear acceleration and head tilting.
72
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72) What detects dynamic equilibrium?
A) cochlea
B) crista ampullaris
C) spiral organ (organ of Corti)
D) utricle and saccule
```
B) crista ampullaris
73
73) What description best matches the function of stereocilia?
A) Stereocilia move up and down when the stapes moves back and forth.
B) Stereocilia transmit movement of the tympanic membrane to the inner ear.
C) Bending of the stereocilia produces depolarization or hyperpolarization in hair cells.
D) Stereocilia are tiny calcium carbonate crystals that increase density in endolymph.
C) Bending of the stereocilia produces depolarization or hyperpolarization in hair cells.
74
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74) Which cranial nerve is responsible for transmitting information about sounds and head position and movement to the brain?
A) facial nerve (CN VII)
B) vestibulocochlear nerve (CN VIII)
C) optic nerve (CN II)
D) olfactory nerve (CN I)
```
B) vestibulocochlear nerve (CN VIII)
75
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75) Neural sensory signals are relayed to the thalamus, EXCEPT for the sensation of:
A) hearing.
B) vision.
C) olfaction.
D) dynamic equilibrium.
```
C) olfaction.
76
76) Where are sensations integrated with memories of past experiences? A) cerebellum
B) limbic system
C) frontal lobe
D) parietal lobe
B) limbic system
77
77) In both general and (most) special sensations, information is first processed by sensory nuclei and then transmitted to the thalamus and to primary cortex areas for awareness and identification.
TRUE
78
78) Like all other sensory pathways, the nerve impulses associated with olfaction are routed through the thalamus on the way to the primary olfactory cortex.
FALSE
79
79) All taste sensations begin with the entry of hydrogen ions into a gustatory cell.
FALSE
80
80) The five major taste sensations are sweet, salty, bitter, sour, and umami.
TRUE
81
81) The conjunctiva is the translucent part of the fibrous layer of the eye.
FALSE
82
82) Six extrinsic eye muscles, including four rectus muscles and two oblique muscles, control the movement of each eye.
TRUE
83
83) The retina is the only portion of the eye to contain photoreceptor cells.
TRUE
84
84) The eye contains two cavities situated within the anterior chamber.
FALSE
85
85) An astigmatism is an irregular curvature of the cornea or lens which causes rays of light to refract unevenly.
TRUE
86
86) Rods are concentrated in the fovea centralis while cones are absent from this region of the retina.
FALSE
87
87) The function of the pharyngotympanic (auditory) tube is to equalize air pressure on both sides of the tympanic membrane.
TRUE
88
88) Endolymph travels within the membranous labyrinth while perilymph travels between the bony and membranous labyrinth.
TRUE
89
89) Neurons on the superior olivary nucleus compare information from both ears to determine the loudness of sound.
FALSE
90
90) When you bend your head, gravity pulls on the otolithic membrane, bending the stereocilia either toward or away from the kinocilium.
TRUE
91
MATCHING PARTS OF THE EYE
| 91) IRIS
C
92
92) Lens
G
93
93) Sclera
A
94
94) Area of retina specialized for detailed vision
H
95
95) Cornea
B
96
96) Portion of the retina that contains no photoreceptors
I
97
MATCHING THE PARTS OF THE EAR
SEE PICTURE
97) Tympanic membrane
C
98
98) External auditory canal
B
99
99) Houses the receptors for hearing
I
100
100) Vestibule
H
101
101) Auditory ossicle that receives vibrations from the tympanic membrane
D
102
102) Semicircular canals
G
103
103) Summarize how the special senses and general senses differ.
There are two significant differences between the special senses and the general senses. First, the general senses rely on the detection of stimuli from receptors that are part of sensory neurons. However, most special senses rely on receptors that are specialized cells rather than sensory neurons. These specialized cells detect specific types of energy or chemicals. Second, the general senses are detected by both cranial nerves and spinal nerves. Special senses are only detected by cranial nerves in the head.
104
104) Explain how a chemical odorant is transduced into a neural signal.
Odorants reach receptors in the cilia of olfactory neurons. The binding of an odorant activates a G-protein which then detaches from the receptor. The G-protein activates an enzyme, adenylate cyclase, to convert ATP into cyclic AMP (cAMP). Finally, cAMP opens ions channels that allow sodium and calcium ions to enter the cell, depolarizing the membrane. Depolarization that reaches threshold at the axon hillock triggers an action potential and transduction has been achieved.
105
105) Explain how the sense of smell is carried into the brain from olfactory neurons.
The axons of the olfactory neurons make up the olfactory nerve. The nerve impulse is carried to the olfactory bulb in the CNS. Olfactory information is carried from the olfactory bulb to the primary olfactory cortex in the temporal lobe. The primary olfactory cortex is responsible for awareness and identification of an odor.
106
106) Summarize the five primary taste sensations.
The five primary taste sensations are sweet, sour, salty, bitter, and umami. Sweet tastes are due to simple sugars such as glucose and fructose. Sour tastes are produced by hydrogen ions, such as those found in citric acid of lemon juice. Salty foods gain their taste from sodium ions. Bitter flavors are imparted by nitrogen-containing compounds and are often found in rancid or poisonous substances. Umami flavors are often associated with meat or broth and produced by glutamate or other amino acids.
107
107) Explain the role G-proteins play in taste sensation.
Receptors for bitter, sweet, and umami compounds activate a G-protein that indirectly closes potassium ion channels involved in the leak current. Due to the activity of the G-protein, the decreased movement of potassium ions out of the cell produces depolarization. Depolarization leads to a graded potential that spreads along the membrane of the small gustatory cells, making an action potential unnecessary.
108
108) Dhara has Sjögren's syndrome, an autoimmune disorder in which the body's white blood cells destroy glands such as the salivary glands. Determine the impact on her sensation of taste.
Dhara will experience diminished taste sensations due to the reduction in saliva production. To reach the taste buds in the crevices between the papillae, a substance must first dissolve in saliva. Once the taste stimulus reaches a gustatory cell, it will be transduced into a neural signal and carried into the brain for awareness and identification.
109
109) Describe the function of the lacrimal gland.
The lacrimal glands release tears and mucus into the conjunctival sac to lubricate and wash away dust and debris from the surface of the eye. Tears produced by the lacrimal gland drain into a series of passages that lead to the nasal cavity.
110
110) A nurse administers pilocarpine eye drops. The nurse instructs the patient to press on the nasolacrimal duct for 30 seconds because the medication can have some systemic side effects, such as affecting the heart rate. Explain the rationale for pressing on the nasolacrimal duct.
The nasolacrimal duct connects the eye to the nasal cavity. Applying pressure to the nasolacrimal duct prevents the drug from traveling from the eye to the nasal mucosa and general circulation, where it may affect heart rate.
111
111) Trace the pathway of tears from the eye to the nose.
The eye and the nasal cavity are connected by a series of passages. Tears from the eyes drain through the lacrimal puncta, to the lacrimal canaliculi, and into the lacrimal sac. The lacrimal sacs are situated in a small depression in the lacrimal bone and carry tears into the nasolacrimal duct. The nasolacrimal duct travels through the lacrimal and maxillary bones into the inferior nasal meatus of the nasal cavity.
112
112) Describe how the iris regulates light entry into the eye during sympathetic and parasympathetic stimulation.
The iris contains two muscles that improve vision by regulating how much light passes through the pupil. The pupillary sphincter muscle contracts following parasympathetic stimulation and constricts the pupil to reduce the amount of light entering the eye. The pupillary dilator muscle is arranged in a radial pattern and contracts following sympathetic stimulation. It enlarges the pupil to permit more light to enter the eye.
113
113) Describe how light is refracted and focused on the retina in an emmetropic eye.
The greatest degree of refraction occurs as light passes from air through the cornea. Additional refraction occurs as light passes through the lens, but less than at the cornea due to the density of the lens. In an emmetropic eye, light from distant objects pass nearly parallel into the eye and need little refraction to be focused on the retina. The cornea provides most of the necessary refraction and the lens, in its flattened shape, provides the rest.
114
114) Explain the difference between accommodation and convergence.
Accommodation occurs when the lens changes shape from flattened to round to increase total refraction for nearby objects. Convergence requires the eyeballs to move medially to view a nearby object and focus the image on the fovea centralis.
115
115) Discuss the two types of photoreceptors and the function of each.
The two types of photoreceptors are rods and cones. Cones contain pigments that allow us to perceive color; they function best in bright light. Rods cannot detect color, but they are sensitive and capable of responding in less intense light. Cones are highly concentrated in the fovea centralis while rods are more important for peripheral vision, which detects images at the edge of our vision.
116
116) Discuss how image-processing occurs in the retina when light strikes photoreceptors.
Rods and cones move from a depolarized state in the dark to a hyperpolarized state in the light. When light strikes photoreceptor cells, light hyperpolarizes the photoreceptor and it stops releasing glutamate. The bipolar cell is free from inhibition and depolarizes, releasing neurotransmitter onto the retinal ganglion cell. The retinal ganglion cell produces action potentials that are sent to the brain via the optic nerve.
117
117) Trace the pathway of an image formed on the retina to the primary visual cortex in the brain.
An image formed on the retina of each eye travels to the optic nerve via the axons of the retinal ganglion cells. The optic nerves meet at the optic chiasma, where axons from the nasal retinas cross to the opposite side. All axons from the opposite visual field then travel into the optic tract to the lateral geniculate nucleus in the thalamus. Axons from the lateral geniculate nucleus form optic radiations and terminate in the primary visual cortex in the medial occipital lobe. At this point, we become consciously aware of visual stimuli.
118
118) Explain the function of the pharyngotympanic (auditory) tube.
The pharyngotympanic tube serves to equalize air pressure on either side of the tympanic membrane. Normally closed and flattened, it opens briefly when we yawn or swallow.
119
119) Discuss the function of the auditory ossicles.
The ossicles play an important role in amplifying and converting sound waves in the air into fluid movement in the inner ear. When the ossicles transmit the force of sound waves from the larger tympanic membrane to the smaller oval window, the force is concentrated in a smaller area and is increased significantly. As a lever system, the ossicles act to amplify the vibration of the oval window. Vibration of the oval window produces pressure waves in the fluid of the inner ear, but more force is needed to generate motion in fluid than in air.
120
120) Discuss the path of nerve impulses from the spiral organ (organ of Corti) to the primary auditory cortex in the brain.
Auditory signals travel through the cochlear portion of the vestibulocochlear nerve (CN VIII) to the cochlear nuclei. The cochlear nuclei project bilaterally to the superior olivary nucleus in the pons. Auditory information is then sent to the inferior colliculus of the midbrain. The auditory information is relayed to the medial geniculate nucleus of the thalamus. The thalamus sends the information to the primary auditory cortex in the superior portion of the temporal lobe where conscious awareness of sound begins, as well as analysis of its location, pitch, and loudness.
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121) Explain how static equilibrium differs from dynamic equilibrium.
Static equilibrium refers to tilting the head and maintaining it in a particular position while dynamic equilibrium refers to maintaining posture during acceleration of the head. Acceleration can occur in a linear direction, such as riding in a car, or in a rotational or angular direction, such as spinning in a rotating chair.
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122) Air travelers report less satisfaction with the taste of food served while flying. Given the dry climate and low humidity in an airplane, predict why food isn't as tasty in the skies.
Both smell and taste are affected by the dry air in the airplane. Olfaction contributes significantly to the sense of taste, so food loses much of its appeal when eaten in an extremely dry environment. Both taste and smell require a moist environment for the chemicals to reach receptors. When odorants reach the olfactory epithelium lining the nasal cavity, they dissolve in the mucus that surrounds the cilia of the olfactory neurons. To reach the taste buds in the crevices between the papillae of the tongue, a substance must first dissolve in saliva. Thus, the dry air of an airplane reduces mucus and saliva, making it more difficult to dissolve chemicals for the sensation of smell and taste.
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123) Explain how rubbing your eyes with dirty hands can lead to an infection in the nasal cavity.
The eye and the nasal cavity are connected by a series of passages. Tears from the eyes can carry an infection through the lacrimal puncta, tiny holes in the medial edge of each eyelid. The puncta are continuous with the lacrimal canaliculi, small ducts that empty into the lacrimal sac. The lacrimal sacs are situated in a small depression in the lacrimal bone and drain tears into the nasolacrimal duct. The nasolacrimal duct travels through the lacrimal and maxillary bones into the inferior nasal meatus of the nasal cavity.
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124) Ginger wears glasses to see distant objects when she drives. She does not need glasses to see objects that are close. Determine the refractive problem she has and how her glasses correct this problem.
Ginger is affected by myopia (nearsightedness). The distance between the cornea and retina is too long (or the cornea curves too much). The lens cannot flatten enough, so light focuses in front of the retina and the image appears blurred. Myopia is corrected with a concave lens that diverges light before it strikes the lens of the eye. The lens can then provide enough refraction to focus light on the retina.
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125) Determine how an upper respiratory infection can impact the ear.
The pharyngotympanic tube connects the middle ear to the nasopharynx. The pharyngotympanic tube acts as a conduit for pathogens in the nasopharynx to reach the middle ear. The resulting inflammation causes a build-up of fluid or pus, and the tympanic membrane bulges painfully into the auditory canal and interferes with hearing.
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126) Explain why eight-year-old Carolina feels like she is still riding the merry-go-round, although she disembarked a few moments ago.
When Carolina's head is in motion, as on the merry-go-round, the endolymph within the semicircular canals lags behind and pushes against the cupula. The endolymph bends the stereocilia, which either increases or decreases glutamate release from the hair cells and causes a corresponding change in the activity of neurons in the vestibular nerve. When she stopped riding the merry-go-round, the endolymph continued to move and bent the cupula in the direction opposite to that when she started turning her head. This has the opposite effect on glutamate release and the activity of the vestibular nerve, and her brain interpreted the change to mean that head rotation has stopped. However, since endolymph lags behind, Carolina continued to have a sensation of movement for a few moments after disembarking the merry-go-round.
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127) Discuss the impact of frontal lobe damage on sensation.
Each primary cortex area has connections with the frontal lobe. The frontal lobe converts all the pieces of information into a meaningful picture. The frontal lobe integrates and analyzes the sensations of taste, smell, sight, and sound. When damage occurs in the frontal lobe, the integration and analysis of these special senses can become impaired.
