The Nervous System Reinforcement and Study Guide Section.1 The Nervous System In your textbook, read about neurons basic units of the nervous system. Complete the table by filling in the missing information in each case. Structure Function 1. carry impulses toward the brain and spinal cord 2. dendrites 3. motor neurons 4. transmit impulses within the brain and spinal cord 5. carry impulses away from neuron cell bodies Order the steps in impulse transmission from 1 to 7. 6. A wave of depolarization moves down the neuron. 7. The Na /K pump takes over again, pumping sodium ions out across the membrane, and pumping potassium ions in. 8. Sodium channels in the neural membrane open. 9. A neuron receives a stimulus. 10. As the wave of depolarization passes, sodium channels close and potassium channels open. 11. The neuron returns to a resting state. 12. Sodium ions flow into the neuron, causing the inside of the neuron to become positively charged. UNIT 10 CHAPTER The Nervous System 89
The Nervous System, continued Reinforcement and Study Guide Section.3 The Effects of Drugs In your textbook, read about how drugs act on the body, their medicinal uses, and abuse of drugs. Answer the following questions. 1. Distinguish between a drug and a medicine. 2. What is a narcotic? 3. Compare the effect of a stimulant on the CNS with the effect of a depressant. 4. What is an addiction? 5. How does a person s body develop a tolerance for a drug? In your textbook, read about the classes of commonly abused drugs. Complete the table by checking the correct column for each example. Example Stimulant Depressant 6. Drugs that cause an increase in heart rate 7. Alcohol 8. Nicotine 9. Caffeine 10. Barbiturates 11. Drugs that cause vasoconstriction 12. Opiates 13. Hallucinogens 92 CHAPTER The Nervous System UNIT 10
The Nervous System Critical Thinking Use with, Section.1 Analyzing Sensory-Somatic Responses T here is more than one kind of reflex. Figure 1 shows the patellar reflex that occurs when a tendon in the knee is suddenly tapped. The action causes a muscle to tense and raise the leg slightly. Simple reflexes such as the patellar reflex are referred to as monosynaptic reflexes. Figure 2 shows Figure 1 MONOSYNAPTIC REFLEX Receptor (neuromuscular) Sensory neuron Synapse what happens when the tip of the finger accidentally comes in contact with a flame. Just as with the patellar reflex, the withdrawal reflex occurs immediately, without first having to consult the brain. Yet it is more complex than the patellar reflex shown in Figure 1 because it is a polysynaptic reflex. Muscle Figure 2 POLYSYNAPTIC REFLEX Motor neuron To brain Muscle Motor neuron Spinal cord Receptor Sensory neuron Interneuron Spinal cord 1. Trace the path of each reflex. How do the two reflexes differ in complexity? 2. The interneurons that transmit a message to motor neurons and cause the withdrawal response also carry information to conscious areas of the brain. Based on this information, explain what advantage a polysynaptic reflex provides over a monosynaptic reflex. 98 CHAPTER The Nervous System UNIT 10
Master 67 Organization of the Nervous System Basic Concepts Use with, Section.1 UNIT 10 CHAPTER The Nervous System 105
Worksheet 67 Organization of the Nervous System Basic Concepts Use with, Section.1 1. What is the control center of the entire nervous system? 2. Which part of the CNS is made up of the midbrain, pons, and medulla oblongata? 3. Which part of the nervous system carries impulses between the body and the central nervous system? 4. List three kinds of neurons that would be involved in a reflex impulse. 5. Which part of the brain sends impulses to the autonomic nervous system during life-threatening emergencies? 6. Compare the parasympathetic nervous system with the sympathetic nervous system. 7. Trace the pathway of impulses through the nervous system in response to feeling rain on your skin. 106 CHAPTER The Nervous System UNIT 10
The Nervous System, continued Assessment Understanding Main Ideas (Part A) In the space at the left, write the letter of the word or phrase that best completes the statement or answers the question. 1. Sensory neurons a. process incoming impulses and pass them on to motor neurons. b. carry impulses from around the body to the brain and spinal cord. c. carry response impulses away from the brain and spinal cord. d. carry impulses across synapses. 2. A nerve impulse travels from one cell to another by passing from a. one axon to another axon. b. one dendrite to an axon. c. one axon to a dendrite. d. one dendrite to another dendrite. 3. Which controls involuntary activities of the body such as breathing and heart rate? a. cerebrum b. cerebellum c. medulla oblongata d. none of these 4. You can see the colors in a picture because you are aided by the a. rods of the retina. b. right visual field. c. cones of the retina. d. left visual field. _ 5. A person who is addicted to a drug is experiencing withdrawal when he or she a. needs more of the drug to achieve the same effect. b. becomes ill after stopping its use. c. needs to take the drug more often. d. feels better when stopping its use. 6. Cocaine is a stimulant because it a. causes blood pressure to drop. b. causes heart rate to slow down. c. relieves anxiety. d. causes vasoconstriction. 7. Alcohol may act on the brain by a. dissolving through the membranes of neurons. b. blocking the movement of sodium and calcium ions. c. increasing anxiety. d. increasing oxygen content. 116 CHAPTER The Nervous System UNIT 10
The Nervous System, continued Assessment Applying Scientific Methods Scientists in western countries have been searching for a chemical that will help curb an alcoholic s appetite for alcohol. Recently, some scientists have been looking at a treatment used in China for over 2000 years. Chinese healers have given alcoholics an extract made from the root of the kudzu vine, which they claim is about 80 percent effective in reducing alcohol craving in patients who have been treated for two to four weeks. Dr. Wing-Ming Keung of Harvard Medical School in Boston visited China to find out what modern researchers thought of the herbal remedy. He spoke to physicians who claimed to have treated 300 human alcohol abusers with the extract. They were convinced that the chemicals in the extract effectively suppressed the patient s appetite for alcohol. After returning to Harvard, Dr. Keung and Dr. Bert L. Vallee decided to try the drug on a group of Syrian golden hamsters in their laboratory. These hamsters were specifically selected because they are known to drink large amounts of alcohol when it is available to them. Suppose you are a member of the Harvard Medical School research team. Your job is to design an experiment that will demonstrate the effectiveness of the kudzu root extract to suppress the hamsters craving for alcohol. 1. Describe the experimental procedure you will follow. 2. What will you use as your control? 3. What will be the variable in your experiment? 4. Predict the results of your experiment. 5. How might you follow up on your experiment? UNIT 10 CHAPTER The Nervous System 119
The Nervous System, continued Assessment Applying Scientific Methods continued 6. Dr. Keung and Dr. Vallee discovered two active ingredients in the root extract, each of which had the effect of lessening alcohol use in the hamsters by 50 percent. The two compounds appeared to interfere with the metabolism, or breakdown, of alcohol in the body. Hypothesize what this discovery may tell us about the nature of alcoholism. 7. How might Dr. Keung and Dr. Vallee s discovery help alcoholics overcome their addition? 120 CHAPTER The Nervous System UNIT 10