The Nervous System

Multiple Choice

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1. There are four levels of organization in the human body: cells, tissues, organs, and organ systems. _________________________ ANS:TDIF:AREF:p. 891 OBJ:35. 1. 1

2. A group of similar cells that perform a single function is called a(an) organ. _________________________

ANS:F, tissue DIF:BREF:p. 891OBJ:35. 1. 1

3. The hypothalamus is to your body as the thermostat is to the internal environment of a house. ________________________ ANS:TDIF:EREF:p. 896 OBJ:35. 1. 2

4. Spreading out from the cell body of a neuron are short, branched extensions called axons. _________________________

ANS:F, dendrites DIF:BREF:p. 898OBJ:35. 2. 1

5. The propagation of an action potential is slower in myelinated axons than in axons that lack a myelin sheath. _________________________ ANS:F, faster DIF:EREF:p. 898OBJ:35. 2. 2

6. The largest and most prominent region of the human brain that is responsible for the voluntary, or conscious, activities of the body is the cerebellum. _________________________ ANS:F, cerebrum DIF:BREF:p. 902OBJ:35. 3. 1

7. The brain and spinal cord can withstand considerable trauma due to the meninges acting as a shock absorber. ______________________________ ANS:F, cerebrospinal fluid DIF:AREF:p. 901OBJ:35. 3. 1

8. If you accidentally step on a tack with your bare foot, the pathway that the nerve impulse takes from your foot to your leg is called a reflex arc. _________________________ ANS:TDIF:BREF:p. 904 OBJ:35. 3. 2 9. The autonomic nervous system is part of the motor division of the peripheral nervous system. _________________________ ANS:TDIF:AREF:p. 904 OBJ:35. 3. 2

10. Chemoreceptors are associated with the sense of smell and touch. _________________________ ANS:F, taste DIF:AREF:p. 909OBJ:35. 4. 1

11. Rods respond to light of different colors, producing color vision. ____________________ ANS:F, Cones DIF:EREF:p. 907OBJ:35. 4. 2

12. A person with a relatively small number of cones in the retinas may have trouble distinguishing colors. _________________________ ANS:TDIF:EREF:p. 907 OBJ:35. 4. 2

13. The cochlea and the two tiny sacs located behind it help the body maintain its equilibrium. ______________________________

ANS:F, semicircular canals DIF:EREF:p. 908OBJ:35. 4. 2

14. Addiction can be defined as intentional misuse of any drug for nonmedical purposes. _________________________

ANS:F, Drug abuse DIF:AREF:p. 914OBJ:35. 5. 1

15. About 40 percent of the fatal accidents that occur on Americans highways involve the drug alcohol. _________________________ ANS:TDIF:BREF:p. 912 OBJ:35. 5. 2

Completion

1. Your skin, hair, nails, and sweat and oil glands make up your _________________________ system.

ANS:integumentary DIF:EREF:p. 892OBJ:35. 1. 1STO:12. A. 4. b

2. Neurons are classified into three types according to the ____________________ the impulse travels.

ANS:direction DIF:AREF:p. 97OBJ:35. 2. 1

3. The process by which a stimulus produces a response that opposes the original stimulus is called ____________________ inhibition. ANS:feedback DIF:BREF:p. 895OBJ:35. 1. 2

4. ____________________ is the process by which organisms maintain a relatively stable internal environment.

ANS:Homeostasis DIF:AREF:p. 895OBJ:35. 1. 2

5. In most animals, axons and dendrites are clustered into bundles of fibers called ____________________.

ANS:nerves DIF:AREF:p. 898OBJ:35. 2. 1

6. Sensory neurons and motor neurons are connected by ____________________, which carry impulses between them.

ANS:interneurons DIF:BREF:p. 897OBJ:35. 2. 1

7. The myelin sheath that surrounds a single long axon leaves many gaps, called ____________________, where the axon membrane is exposed. ANS:nodes DIF:AREF:p. 898OBJ:35. 2. 1

8. The difference in electrical charge across the cell membrane of a resting neuron is its resting ____________________.

ANS:potential DIF:AREF:p. 898OBJ:35. 2. 2

9. The two major divisions of the human nervous system are the central and the ____________________ nervous systems.

ANS:peripheral DIF:BREF:p. 901OBJ:35. 3. 1 Figure 35–3

10. The process illustrated in Figure 35–3 is called a(an) ____________________.

ANS:reflex arc DIF:EREF:p. 904OBJ:35. 3. 2

11. The turning of your head is controlled by the ____________________ nervous system, which is part of the peripheral nervous system’s motor division.

ANS:somatic DIF:EREF:p. 903OBJ:35. 3. 2

12. Sensory receptors called _________________________ are found in the skin, skeletal muscles, and inner ears and are sensitive to touch, pressure, stretching of muscles, sound, and motion.

ANS:mechanoreceptors DIF:BREF:p. 906OBJ:35. 4. 1

13. Small muscles attached to the ____________________ of your eye change its shape to help you focus on near or distant objects.

ANS:lens DIF:EREF:p. 907OBJ:35. 4. 2

14. The class of drugs called ____________________ mimic natural chemicals in the brain known as endorphins, which normally help to overcome sensations of pain.

ANS:opiates DIF:EREF:p. 911OBJ:35. 5. 1

15. Cirrhosis of the liver is a possible result of the long-term use of ____________________.

ANS:alcohol DIF:BREF:p. 913OBJ:35. 5. 2STO:11. A. 4. c, 13. A. 4. b

Short Answer

1. Compare and contrast tissues and organs.

ANS: A tissue is a group of similar cells that perform a single function. An organ is a group of tissues that work together to perform a complex function.

DIF:AREF:p. 891OBJ:35. 1. 1

2. What is homeostasis? ANS: Homeostasis is the process by which organisms keep internal conditions relatively constant despite changes in external environments.

DIF:BREF:p. 895OBJ:35. 1. 2

3. How can the nervous system help a person run without falling? Explain.

ANS: Balance is necessary for running. Portions of the nervous system, along with the sense organs, can interpret a person’s balance and make minor corrections to make sure the person will not fall.

DIF:EREF:p. 908OBJ:35. 4. 1

4. Distinguish between the functions of dendrites and axons.

ANS: Dendrites and axons are parts of a neuron. Dendrites carry impulses from the environment or from other neurons toward the cell body. Axons carry impulses away from the cell body.

DIF:BREF:p. 898OBJ:35. 2. 2

5. At what location does a neuron transfer an impulse to another cell? ANS: the synapse

DIF:AREF:p. 900OBJ:35. 2. 2 Figure 35–1

7. What are the major regions of the brain?

ANS: The major regions of the brain are the cerebrum, the cerebellum, the brain stem, the thalamus, and the hypothalamus.

DIF:BREF:p. 901, p. 902, p. 903OBJ:35. 3. 1

8. How is the spinal cord like a major telephone line?

ANS: The spinal cord is the main communications link between the brain and the rest of the body, transmitting information, just as a telephone line carries many calls at once.

DIF:AREF:p. 903OBJ:35. 3. 1

9. Why is a severe injury to the brain stem usually fatal?

ANS: The brain stem controls some of the body’s most important functions, including breathing, heartbeat, blood pressure, and swallowing. These involuntary processes are essential to life, so the disruption of any of these processes can cause death.

DIF:EREF:p. 902OBJ:35. 3. 1

10. What is a motor neuron?

ANS: A motor neuron carries impulses from the brain and the spinal cord to muscles and glands.

DIF:EREF:p. 897OBJ:35. 2. 1

11. How is a pain in your toe perceived by sensory receptors? Why is it important for your body to sense this pain?

ANS: Pain receptors respond to chemicals released by the damaged cells in your toes, which may indicate danger, injury, or disease.

DIF:EREF:p. 906OBJ:35. 4. 1

12. Identify the five main senses.

ANS: The five main senses are vision, hearing, smell, taste, and touch.

DIF:BREF:p. 906OBJ:35. 4. 2

13. Compare and contrast the functions of rods and cones.

ANS: Both rods and cones are photoreceptors in the retina. Rods are sensitive to light but do not distinguish colors. Cones are less sensitive to light than rods, but cones respond to light of different colors.

DIF:AREF:p. 907OBJ:35. 4. 2

14. How do opiates help people overcome sensations of pain?

ANS: Opiates mimic natural chemicals in the brain known as endorphins, which normally help to overcome sensations of pain.

DIF:BREF:p. 911OBJ:35. 5. 1

15. What are the cause and effects of fetal alcohol syndrome?

ANS: Fetal alcohol syndrome is caused by consuming alcohol while pregnant. The effect of this syndrome is a range of birth defects in the baby, such as heart defect, malformed face, delayed growth, and poor motor development.

DIF:AREF:p. 913OBJ:35. 5. 2STO:11. A. 4. c, 13. A. 4. b

Essay

1. How are the cells of the human body similar to individuals in a society that work in groups to accomplish shared goals?

ANS: Every cell in the human body is both an independent unit and an interdependent part of a larger community—the entire organism.

Similarly, each individual in a society can survive independently, but it is also necessary to form interdependent groups to accomplish certain goals.

DIF:EREF:p. 891OBJ:35. 1. 1

2. Name six of the body’s systems and describe their functions.

ANS: Answer should include six of the following systems. The nervous system coordinates the body’s response to changes in its internal and external environment. The integumentary system serves as a barrier against infection and injury, helps to regulate body temperature, and provides protection against ultraviolet radiation from the sun.

The skeletal system supports the body, protects internal organs, allows movement, stores mineral reserves, and provides a site for blood cell formation. The muscular system works with the skeletal system to provide voluntary movement and helps to circulate blood and move food through the digestive system. The circulatory system brings oxygen, nutrients, and hormones to cells; fights infection; removes cell wastes, and helps regulate body temperature. The respiratory system provides the oxygen needed for cellular respiration and removes excess carbon dioxide from the body.

The digestive system converts foods into simpler molecules that can be used by the cells of the body. The excretory system eliminates waste products from the body. The endocrine system controls growth, development, and metabolism. The reproductive system produces reproductive cells and, in the female, nurtures and protects the developing embryo. The lymphatic system helps protect the body from disease, collects fluid lost from blood vessels, and returns the fluid to the circulatory system.

DIF:EREF:p. 892, p. 893OBJ:35. 1. 1 STO:12. A. 4. b

3. Based on the process of feedback inhibition, explain how your body maintains a relatively constant temperature.

ANS: The hypothalamus contains nerve cells that monitor both the temperature of your skin at the surface of the body and the temperature of organs in the body’s core. When these nerve cells sense that the body’s temperature is lower than normal, the hypothalamus produces chemicals that signal cells throughout the body to speed up their activities. The heat produced by this increase in cellular activity causes a gradual rise in body temperature, which is detected by the nerve cells in the hypothalamus.

This feedback inhibits the production of chemicals that speed up cellular activity and keeps body temperature from rising to a dangerous level. If your body temperature rises too far above normal, the hypothalamus slows down cellular activities, minimizing the production of heat.

DIF:EREF:p. 895OBJ:35. 1. 2

4. Compare resting potential and action potential in a neuron.

ANS: The difference in electrical charge across the cell membrane of a resting neuron is the resting potential. Once an impulse begins, positive ions rush across the cell membrane, reversing the charge difference.

The inside of the membrane gains a positive charge, and the outside of the membrane gains a negative charge. This rapid reversal of charges is called the action potential. As the impulse passes, the positively charged ions flow out of the cell, and the resting potential of the membrane is reestablished.

DIF:AREF:p. 898, p. 899OBJ:35. 2. 2

5. What is the function of each of the main regions of the brain?

ANS: The cerebrum controls voluntary activities, intelligence, learning, and judgment. The cerebellum controls coordination and balance.

The brain stem controls blood pressure, heart rate, breathing, and swallowing. The thalamus receives messages from the sense organs. The hypothalamus recognizes sensations of hunger, thirst, fatigue, anger, and body temperature.

DIF:AREF:p. 902, p. 903OBJ:35. 3. 1

6. Compare the effects of the sympathetic and the parasympathetic divisions of the autonomic nervous system.

ANS: The sympathetic nervous system and the parasympathetic nervous system each release different neurotransmitters that have opposite effects on the same organ system, which helps the body maintain homeostasis.

When the sympathetic system speeds up an activity, the parasympathetic system slows down the same activity. For example, the heart rate is increased by the sympathetic nervous system but decreased by the parasympathetic nervous system.

DIF:AREF:p. 904OBJ:35. 3. 2

7. What are the five general categories of sensory receptors? Where are they located in the body?

ANS: The five general categories are pain receptors, thermoreceptors, mechanoreceptors, chemoreceptors, and photoreceptors. Pain receptors are throughout the body except in the brain.

Thermoreceptors are located in the skin, body core, and hypothalamus. Mechanoreceptors are found in skin, skeletal muscles, and inner ears. Chemoreceptors are found in the nose and taste buds. Photoreceptors are found in the eyes.

DIF:AREF:p. 906OBJ:35. 4. 1

8. How would you design an experiment to show that much of what people actually taste in food depends on their sense of smell?

ANS: Students’ experiments may include having someone taste different types of foods that have specific tastes and smells, and then having the person taste them with his or her eyes shut and nose held closed.

Students should determine if the person can identify the food that he or she tasted without the use of sight and smell, and record observations and draw conclusions.

DIF:EREF:p. 909OBJ:35. 4. 2

9. People who have to drive long distances sometimes take stimulants. How might this practice be dangerous?

ANS: Stimulants increase the release of neurotransmitters at some synapses in the brain, which then leads to a feeling of energy and well-being. However, when the effects of the stimulants wear off, the brain’s supply of neurotransmitters has been depleted.

The user quickly falls into fatigue and depression, which can impair the person’s ability to drive and could lead to accidents.

DIF:AREF:p. 910OBJ:35. 5. 1

10. In the Designated Driver Program, one person in a group agrees to be the driver and not to drink any alcohol. Why is this program important?

ANS: By decreasing the number of drunk drivers on the road, you decrease your chances of being involved in such an accident. If more people were involved in the Designated Driver Program, fewer people would be in danger of being involved in a fatal accident.

DIF:EREF:p. 912OBJ:35. 5. 2

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