CHAPTER SEVEN
Answers to End of Chapter Review Questions
Questions appear on pp. 275–277
Multiple Choice
1. d (p. 226)
2. a, b, c (pp. 232, 241, 254; Table 7.1)
3. d (p. 247)
4. d (p. 232)
5. c (p. 246)
6. 1-g; 2-d; 3-f; 4-b; 5-e; 6-h; 7-a (pp. 241, 245–247; Table 7.1)
7. a, c (pp. 254, 261)
8. c (p. 254)
9. a, c (pp. 258-260; Figure 7.24; Table 7.2)
10. a, c (p.262; Table 7.3)
11. d (p. 228)
12. d (pp. 264265; Figure 7.27)
Short Answer Essay
13. Nervous system and endocrine system. (p. 225)
14. The structural classification includes all the nervous system organs. The major subdivisions are the central nervous system which includes the brain and spinal cord, and the peripheral nervous system which is mainly nerves. The functional classification divides the peripheral nervous system into afferent (sensory) and efferent (motor) branches. The motor division is further divided into the somatic and autonomic branches. (pp. 226-227; Figure 7.2)
15. The functional classification of neurons is based on the general direction of the impulse. Impulses traveling from sensory receptors to the CNS are afferent (sensory) neurons. Impulses traveling from the CNS to effector organs travel along efferent (motor) neurons. Neurons that are in the CNS and connect afferent and efferent pathways are called interneurons or association neurons. (pp. 232-233)
16. Neurons are the “nervous cells.” They exhibit irritability and conductivity. The major functions of the neuroglia are protection, support, myelination, and a nutritive/metabolic function relative to the neurons. Schwann cells are myelinating cells in the peripheral nervous system. (pp. 227–229)
17. A threshold stimulus causes a reversal in membrane permeability that allows Na+ to enter the neuron through Na+ gates. This causes local depolarization and generates the action potential, which is then self-propagating. This event is quickly followed by a second permeability change that restricts Na+ entry, but allows K+ to leave the neuron, causing repolarization or resumption of the polarized state. One-way conduction occurs at synapses because axons (not dendrites) release the neurotransmitter. (pp. 229, 234–236)
18. Pain receptors, such as free/bare nerve endings; Pacinian corpuscles (deep pressure receptors) and Meissner’s corpuscles (touch receptors); Golgi tendon receptors and muscle spindle receptors (proprioreceptors). The pain receptors are most numerous because pain indicates actual or possible tissue damage. (p. 233; Figure 7.7)
19. The minimum components of a reflex arc include a receptor, an afferent neuron, an integration center, an efferent neuron, and an effector. (pp. 237-238; Figure 7.11)
20. Student drawings and responses can be checked by referring to Figure 7.13 and pp. 240-243.
21. The pons also has important nuclei that participate in the control of respiratory rhythm. The medulla is vital because it contains the major respiratory centers, the vasomotor center (which controls blood vessel diameter, hence blood pressure), and the cardiac centers. Without breathing and heart activity, life stops. (pp. 241, 246-247; Table 7.1)
22. The thalamus is a relay station for sensory impulses ascending to the cerebral cortex for interpretation; as impulses pass through the thalamus, one crudely senses that the incoming stimulus is pleasant or unpleasant. The thalamus also eliminates redundant information/input. The hypothalamus is a major autonomic clearing center whose important functions include temperature regulation, water balance, and metabolic control; it also serves as an important center for emotions and drives (sex, rage, pleasure, satiety/appetite, thirst), as a member of the limbic system. (pp. 241, 245-246; Table 7.1)
23. Bone: Enclosed by the skull. (p. 247) Membranes: The meningeal membranes—dura mater, arachnoid mater, and pia mater—enclose the brain within the skull and provide a passage for the circulation of CSF and its return to the blood. (pp. 247, 249) Fluid: Cerebrospinal fluid (CSF) cushions the brain from physical trauma. (pp. 247-248, 250) Capillaries: The capillaries of the brain are permeable only to glucose, a few amino acids, and respiratory gases. Hence, they protect the brain from possibly harmful substances in the blood. (pp. 250-251)
24. Gray matter is neural tissue composed primarily of nerve cell bodies and unmyelinated fibers. White matter is composed primarily of myelinated fibers (p. 232). In the cerebral hemispheres, most of the gray matter is outermost (superficial), and the white matter is deep (p. 240). In the spinal cord, the white matter is superficially located and the gray matter is internal or deep. (p. 254)
25. Major reflex center; pathway for ascending sensory impulses and descending motor impulses. (p. 252)
26. Twelve pairs. Purely sensory: Olfactory (I), optic (II), and vestibulocochlear (VIII). Activates the chewing muscles: trigeminal (V). Regulates heartbeat, etc.: Vagus (X). (pp. 257-259; Table 7.1)
27. The head and neck region. (p. 257)
28. Thirty-one pairs. They arise from the dorsal (sensory) and ventral (motor) roots of the spinal cord. (p. 257)
29. Dorsal rami: Posterior body trunk. Ventral rami: Limbs and anterior, lateral body trunk. (p. 257)
30. Cervical plexus: Diaphragm, shoulder and neck muscles. Brachial plexus: Arm, forearm, wrist, and hand. Lumbar plexus: Lower abdomen, buttocks, anterior thigh, medial thigh, anteromedial leg. Sacral plexus: Lower posterior trunk, posterior thigh, leg, and foot. (p.262; Table 7.2)
31. The autonomic nervous system has a chain of two motor neurons (rather than one) extending from the CNS and is controlled involuntarily (rather than voluntarily). The ANS has different effector organs (cardiac muscle, smooth muscle, and glands), and it can release both acetylcholine (parasympathetic nervous system) and norepinephrine (sympathetic nervous system). This system has cell bodies of motor neurons inside and outside the CNS. Also, the two divisions of the ANS have antagonist actions to each other. (pp. 26-265; Figure 7.27)
32. The parasympathetic division of the ANS is the “housekeeping system.” It acts to conserve body energy and to keep the body running at minimum levels of energy use during nonemergency periods. Its effect is seen primarily in the normal operation of the digestive system and the urinary system. The sympathetic division is the “fight-or-flight” system; it acts during periods of short-term stress to increase heart rate and blood pressure to increase oxygen levels in the body, as well as increasing blood glucose levels, and to shunt blood to necessary organs. Generally, sympathetic activity inhibits digestive system functioning. The parasympathetic system has the opposite effect. (pp. 266–269; Table 7.4)
33. Although both the sympathetic and parasympathetic preganglionic fibers release acetylcholine, their postganglionic fibers (in close contact with the effector organs) release different neurotransmitters. The sympathetic fibers release norepinephrine and the parasympathetic fibers release acetylcholine. These different neurotransmitters produce opposing effects in the effector organs. (pp. 265–269; Figure 7.27)
34. Schwann cells produce myelin outside the CNS. They are specialized support cells that wrap tightly around an axon in a jelly roll fashion and enclose it. As a result, the neuron is insulated. (p. 229)
35. Both CVAs and TIAs result from restricted blood flow to brain tissue. CVAs result in permanent or long-lasting deficits, including paralysis, aphasias, and visual disturbances. In TIAs, the disturbances, though similar, are temporary because neurons do not die, since there is only a transient restricted blood flow to the area. However, TIAs are warning signs for CVAs in the future. (pp. 251-252)
36. Senility is age-related mental deterioration (i.e., changes in intellect, memory, etc.). Permanent causes include factors that deprive neurons of adequate oxygen (such as arteriosclerosis) and degenerative structural changes (as in Alzheimer’s disease). Reversible causes include drug effects, low blood pressure, poor nutrition, and hormone imbalances. (p. 271)
Answers to Critical Thinking and Clinical Application Questions
37. Senility. (p. 271)
38. Hypoglossal (XII). (pp. 258-259, 260; Table 7.2, Figure 7.24)
39. The parasympathetic division is involved in the activation of the digestive viscera and with conserving body energy. Following a meal, this system promotes digestive activity and lowers the heart rate and the respiratory rate. The sympathetic division is only minimally active at this time. Therefore, the person will feel “very sleepy.” If the person is overweight, he probably should not overexert himself. However, doing the dishes would not be hazardous to his health. (p. 268; Table 7.4)
40. Intracranial hemorrhage. (p. 251)
41. Sternocleidomastoid and trapezius muscles. (pp.258-259; Table 7.2)
42. Cerebral palsy—it will not get worse. (p. 269)
43. Brachial plexus. (p.262; Table 7.3)
44. Schwann cells and oligodendrocytes deposit a fatty coat called myelin around axons. Like the rubber coat around household wires, myelin acts as an electrical insulator. (pp. 229-230)
45. The reticular activating system was damaged. (p. 246)
46. The nervous system is formed during the first month of development so exposure to toxins at this time will cause great neural damage. (p. 269)
47. The femoral nerve, which originates at lumbar vertebrae one, two, three, and four (p. 262; Table 7.3), experienced trauma by hockey stick. The femoral motor nerve innervates the rectus femoris muscle, which is the only one of the four quadriceps muscles that cause both hip joint flexion and knee joint extension. This nerve is also responsible for cutaneous sensation in that area. Jason is not feeling any pain, which further indicates femoral nerve damage..
48. Accessory (IX) nerves. (pp.258-259; Table 7.2)
49. By changing the outside environment by feeling the wind while driving, or turning up the volume on the car stereo, or drinking the cold water, Taylor is taking her body out of a “habituation” state by introducing new environmental stimuli. This allows her brain to receive new sensory input (through her skin, ears, and mouth, integrate the information, and allow for motor output to potentially increase her oxygen intake through higher heart and respiratory rate through the activation of the sympathetic division. Potentially the limbic system may also be activated as well (p.226; Figure 7.2)
50. The sensory receptors in the nose (olfactory receptors) detected the coffee aroma, and that information was sent up the olfactory nerve to the olfactory cortex, which is associated with the limbic system, of which the hypothalamus is a member. The hypothalamus, the autonomic control center, sends back instructions via the vagus nerve to the mouth and stomach for activation, a parasympathetic division response. It is most likely a conditioned reflex, where the smell of coffee was paired with breakfast, and therefore the salivation and stomach rumbling occurred. (pp. 245-246, 258-259, 267-268; Table 7.2)