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Laboratory
14
Nervous System and Senses
(LM pages 187–202)
Time Estimate for Entire Lab: 2.0 hours
Seventh Edition Changes
This was lab 13 in the previous edition.
New or revised figures: 14.2 The human brain
MATERIALS AND PREPARATIONS1
All Exercises
Models. Posters or good-quality 35-mm color slides of models can be used in place of models.
14.1 The Mammalian Brain (LM pages 188-190)
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sheep brain, preserved (Carolina 22-8770)
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human brain, model (a number of models are available; see Carolina’s “Models” section)
14.2 Spinal Nerves and Spinal Cord (LM pages 191-193)
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slide, prepared: spinal cord, cross section (Carolina 31-3738, -3744)
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microscopes, compound light
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lens paper
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index card, any size
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meterstick
14.3 The Human Eye (LM pages 193-196)
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model, human eye (a number of models are available; see Carolina’s “Models” section)
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pencil
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meterstick
14.4 The Human Ear (LM pages 197-198)
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model, human ear (a number of models are available; see Carolina’s “Models” section)
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tuning fork (various) or two spoons
14.5 Sensory Receptors in Human Skin (LM pages 198-199)
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model, human skin (Carolina 56-7665, -7671, -7676)
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scissors, fine point; or hairpin
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beakers, 1,000 ml, three
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water: ice-cold, room-temperature, warm
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thermometer, Celsius
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ice
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cotton swabs
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5% sucrose solution (Carolina 89-2860)
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0.1% quinine sulfate solution (Carolina 88-6050, -6052)
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10% NaCl solution
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5% acetic acid solution (acetic acid, glacial, Carolina 84-1292)
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rubber or latex examining gloves
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carrots, fresh peeled, cut same size and shape
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apples, fresh peeled, cut same size and shape
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distilled water
1 Note: “Materials and Preparations” instructions are grouped by exercise. Some materials may be used in more than one exercise.
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5% sucrose. Add 5 g of sucrose to 100 ml of distilled water.
0.1% quinine sulfate solution. Add 0.1 g of quinine sulfate to 100 ml of distilled water.
10% NaCl (sodium chloride). Add 10 g of NaCl to 100 ml of distilled water.
0.5% acetic acid. Add 0.5 ml of glacial acetic acid to 100 ml of distilled water.
EXERCISE QUESTIONS
14.1 The Mammalian Brain (LM pages 188-190)
Observation: The Human Brain (LM page 190)
State two general observations about a difference in the structure of the brain between sheep and
humans.
1. The size of the brain (relative to body size) increases.
2. The size of the cerebrum in relation to the rest of the brain increases.
14.2 Spinal Nerves and Spinal Cord (LM pages 191-193)
Spinal Nerves (LM page 191)
1. Why is this neuron called a sensory neuron? It conveys nerve impulses from the sensory receptor to the
spinal cord.
2. Why is this neuron called an interneuron? It transmits impulses from the sensory neuron to the motor
neuron.
3. Why is this neuron called a motor neuron? It conveys impulses from the spinal cord to an effector
(muscle or gland).
Spinal Reflexes (LM page 192)
Ankle (Achilles) Reflex (LM page 193)
3. Which way does the foot move? Does it extend (move away from the knee) or flex (move toward
the knee)? The foot extends.
Knee-Jerk (Patellar) Reflex (LM page 193)
3. In this relaxed state, does the leg flex (move toward the buttocks) or extend (move away from the
buttocks)? The leg extends.
14.3 The Human Eye (LM pages 193-196)
Observation: The Human Eye (LM page 193)
2. Trace the path of light from outside the eye to the retina. Light travels through the cornea, the anterior
chamber filled with aqueous humor, through the pupil, the lens, and the posterior cavity filled with vitreous
humor before reaching the retina.
3. Which structure holds the lens and is involved in accommodation? the ciliary body
4. Which of the structures listed in Table 14.1 aid in refracting and focusing light rays? lens, cornea,
and humors
5. Specifically, what are the sensory receptors for sight, and where are they located in the eye? The
receptors are the rod cells and cone cells, which are located in the retina.
6. What structure takes nerve impulses to the brain from the rod cells and cone cells? the optic nerve
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Experimental Procedure: Blind Spot of the Eye (LM page 195)
Left Eye (LM page 195)
6. Measure the distance. . . when the circle first disappeared. Distances will vary with the individual.
Generally, the blind spot is within 40 cm of the eye.
Right Eye (LM page 195)
6. Measure the distance. . . when the cross first disappeared. Distances will vary with the individual.
Generally, the blind spot is within 40 cm of the eye.
Experimental Procedure: Accommodation of the Eye (LM page 196)
5. Measure the distance (in centimeters) between the pencil and your eye. Distances will vary with the
individual.
6. At what distance can your eye no longer accommodate for distance? Distances will vary with the individual.
7. If you wear glasses . . . note the accommodation distance of your eye without glasses. Distances will
vary with the individual.
8. How “old” is the eye you tested? Answers will vary with the individual.
14.4 The Human Ear (LM pages 197-198)
Experimental Procedure: Locating Sound (LM page 198)
4. a.–e. Record the subject’s perceptions. Perceptions will vary with the individual.
5. Is there an apparent difference in hearing between your two ears? Answers will vary with the
individual.
14.5 Sensory Receptors in Human Skin (LM pages 198-199)
Observation: Human Skin (LM page 198)
With the help of a model of human skin . . . describe the location of each (structure):
1. Subcutaneous layer
beneath dermis
2. Adipose tissue
within subcutaneous layer
3. Dermis
beneath epidermis
4. Epidermis
uppermost part of skin
5. Hair follicle and hair
begin in dermis and continue through epidermis to outside
6. Oil gland
opens into hair follicle in dermis
7. Sweat gland
begins in dermis and continues through epidermis to outside
8. Sensory receptors
largely found in dermis
Experimental Procedure: Touch Receptors (LM page 199)
5. a.–d. Record the shortest distance . . . for a two-point discrimination in the following areas:
Distances will vary with the individual.
6. Which of these areas apparently contains the greatest density of touch receptors? the fingers
Why is this useful? This sensitivity enables humans to manipulate tools.
Experimental Procedure: Temperature Receptors (LM page 199)
4. Record the sensation in the right and left hands.
a. Right hand
feels warm
b. Left hand
feels cold
5. Explain your results. Each hand has accommodated to the temperature of the first beaker.
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14.6 Human Chemoreceptors (LM pages 200-201)
Experimental Procedure: Taste Receptors (LM page 200)
Taste (LM page 200)
Table 14.4 Taste Sensations
Results will depend on the individual being tested
Taste and Smell (LM page 201)
Table 14.5 & 14.6 Taste and Smell Experiment
Results will depend on the individual being tested.
Conclusions (LM page 201)
• Answers to all three questions will depend upon students’ results.
LABORATORY REVIEW 14 (LM page 202)
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What portion of the brain is largest in humans? cerebrum
What portion of the brain controls muscular coordination? cerebellum
What is the most inferior portion of the brain stem? medulla oblongata
What structures protect the spinal cord? vertebrae
Are motor neuron cell bodies located in the gray or white matter of the spinal cord? gray matter
What type of neuron is found completely within the CNS? interneuron
Which neuron’s cell body is in the dorsal root ganglion? sensory neuron
What part of the eye contains the sensory receptors for sight? retina
Where on the retina is the blind spot located? where the optic nerve exits the retina
What do you call the outer layer of the eye? sclera
What part of the ear contains the sensory receptors for hearing? inner (cochlea)
Where in relation to the head is it most difficult to detect the location of a sound? above the head
In which portion of the ear are the malleus, incus, and stapes located? middle
What layer of the skin contains sensory receptors? dermis
Are touch receptors distributed evenly or unevenly in the skin? unevenly
What senses are dependent on chemoreceptors? taste and smell
The four taste sensations are sour, salty, bitter, and sweet.
Thought Questions
18. Trace the path of light in the human eye—from the exterior to the retina. How do nerve impulses
from the retina reach the brain? Light travels through the cornea, the anterior chamber filled with aqueous
humor, through the pupil, the lens, and the posterior cavity filled with vitreous humor before reaching the retina. Nerve impulses travel in the optic nerve to the brain.
19. Trace the path of sound waves in the human ear—from the tympanic membrane to the sensory
receptors for hearing. Sound travels from the tympampic membrane to the malleus, to the incus, to the
stapes, to the fluid within the cochlea, which contains hair cells, the sensory receptors for hearing.