NERVOUS SYSTEM STUDY GUIDE 1 MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) Which of the following is not a function of the formed by nervous system? A) oligodendrocytes. A) integrate sensory information B) astrocytes. B) sense the internal and external environments C) satellite cells. C) direct long-term functions, such as growth D) ependymal cells. D) coordinate voluntary and involuntary activities E) microglia. E) control peripheral effectors 2) The ________ nervous system is composed of the 10) ________ line the brain ventricles and spinal canal. brain and spinal cord. A) Satellite cells A) afferent B) autonomic C) central D) peripheral E) B) Astrocytes efferent C) Microglia 3) The ________ nervous system controls the skeletal D) Oligodendrocytes muscles. E) Ependymal cells A) parasympathetic 11) Small, wandering cells that engulf cell debris and B) afferent pathogens in the CNS are called C) somatic A) satellite cells. D) autonomic B) microglia. E) sympathetic C) astrocytes. 4) The part of the peripheral nervous system that carries D) ependymal cells. sensory information to the CNS is designated E) oligodendrocytes. A) motor. 12) The neurilemma of axons in the peripheral nervous B) somatic. system is formed by C) afferent. A) oligodendrocytes. D) autonomic. B) microglia. E) efferent. C) satellite cells. 5) Which of the following is not a function of the D) astrocytes. neuroglia? E) Schwann cells. A) secretion of cerebrospinal fluid 13) Glial cells that surround the neurons in ganglia are B) maintenance of blood-brain barrier A) microglia. C) phagocytosis B) astrocytes. D) memory C) ependymal cells. E) support D) satellite cells. 6) Which of the following are a type of glial cell found in E) oligodendrocytes. the peripheral nervous system? 14) Which of the following is not a recognized structural A) satellite cells classification for neurons? B) ependymal cells A) bipolar C) microglia B) unipolar D) astrocytes C) pseudopolar E) oligodendrocytes D) multipolar 7) The largest and most numerous of the glial cells in the E) anaxonic central nervous system are the 15) The most abundant class of neuron in the central A) microglia. nervous system is B) oligodendrocytes. A) bipolar. C) satellite cells. B) multipolar. D) astrocytes. C) anaxonic. E) ependymal cells. D) pseudopolar. 8) Functions of astrocytes include all of the following, E) unipolar. except 16) The cytoplasm that surrounds the nucleus of a A) responding to neural tissue damage. neuron is called the B) maintaining the blood-brain barrier. A) neuroplasm. C) conducting action potentials. B) protoplasm. D) guiding neuron development. C) nucleoplasm. E) forming a three-dimensional framework for the CNS. D) sarcoplasm. 9) The myelin sheath that covers many CNS axons is E) perikaryon. B) bipolar. 17) Clusters of RER and free ribosomes in neurons are C) multipolar. called D) tripolar. A) microglia. E) anaxonic. B) neurofibrils. 26) Neurons that have one axon and one dendrite, with C) perikaryon. the soma in between, are called D) Nissl bodies. A) anaxonic. E) neurofilaments. B) tripolar. 18) The axon is connected to the soma at the C) bipolar. A) synapse. D) unipolar. B) collaterals. E) multipolar. C) axon hillock. 27) Neurons that have several dendrites and a single D) synaptic knobs. axon are called E) telodendria. A) unipolar. B) multipolar. 19) Branches that may occur along an axon are called C) tripolar. A) collaterals. D) bipolar. B) synapses. E) anaxonic. C) synaptic knobs. D) telodendria. E) hillocks. 20) Axons terminate in a series of fine extensions known as A) dendrites. 28) Sensory neurons of the PNS are B) synapses. A) unipolar. C) telodendria. B) anaxonic. D) knobs. C) tripolar. E) collaterals. D) bipolar. 21) Neurotransmitter for release is stored in synaptic E) multipolar. A) telodendria. 29) Which of the following activities or sensations is not B) mitochondria. monitored by interoceptors? C) vesicles. A) cardiovascular activities D) neurosomes. B) sight E) knobs. C) urinary activities 22) The site of intercellular communication between D) taste neurons is the E) activities of the digestive system A) synaptic knob. 30) Which of the following is not involved in creating B) collateral. the resting potential of a neuron? C) synapse. A) membrane permeability for potassium ions greater D) hillock. than sodium ions E) telodendria. B) The interior of the plasma membrane has an excess of 23) The rabies virus travels to the CNS via negative charges. A) blood vessels. C) diffusion of sodium ions into the cell B) subcutaneous connective tissue. D) diffusion of potassium ions out of the cell C) retrograde axoplasmic transport. E) membrane permeability for sodium ions greater than D) anterograde axoplasmic transport. potassium ions E) cerebrospinal fluid. 31) Which of the following interactions between 24) Neurons that are rare, small, and lack features that electrical and chemical gradients does not lead to the distinguish dendrites from axons are called establishment of a neuron's resting potential? A) unipolar. A) Chemical and electrical forces both favor sodium ions B) multipolar. entering the cell. C) anaxonic. B) Potassium ions are repulsed by positive charges D) bipolar. outside the cell. E) tripolar. C) Potassium ions are attracted to the negative charges 25) Neurons in which dendritic and axonal processes are inside the cell. continuous and the soma lies off to one side are called D) Electrical forces push sodium ions out of the cell. A) unipolar. E) Chemical forces tend to drive potassium ions out of the cell. E) must reestablish ion concentrations after each action 32) At the normal resting potential of a typical neuron, potential. its Na-K ion exchange pump transports 38) The all-or-none principle states that A) 2 intracellular sodium ions for 1 extracellular A) all stimuli great enough to bring the membrane to potassium ion. threshold will produce identical action potentials. B) 3 extracellular sodium ions for 2 intracellular B) all stimuli will produce identical action potentials. potassium ions. C) the greater the magnitude of the stimuli, the greater C) 3 intracellular sodium ions for 2 extracellular the magnitude of the action potential. potassium ions. D) only motor stimuli can activate action potentials. D) 3 intracellular sodium ions for 1 extracellular E) only sensory stimuli can activate action potentials. potassium ion. 39) In the process of continuous action potential E) 1 intracellular sodium ion for 2 extracellular propagation, potassium ions. A) the action potential is triggered by graded 33) Ion channels that are always open are called depolarization of the initial segment. ________ channels. B) at threshold, sodium channels begin to open rapidly. A) regulated B) active C) local D) gated E) leak C) local currents depolarize the region just adjacent to 34) Opening of sodium channels in the axon membrane the active zone. causes D) local currents depolarize a sensitive spot distant from A) depolarization. the active zone. B) repolarization. E) A, B, and C C) hyperpolarization. 40) In the process of saltatory action potential D) increased positive charge inside the membrane. propagation, E) both A and D A) the action potential is triggered by graded 35) Voltage-gated channels are present depolarization of the initial segment. A) on the soma of neurons. B) at threshold, sodium channels begin to open rapidly. B) at the motor end plate. C) local currents depolarize the region just adjacent to C) along the perikaryon of neurons. the active zone. D) in the membrane that covers axons. D) local currents depolarize a sensitive spot distant from E) on the surface of dendrites. the active zone. E) A, B, and D 41) Which of the following does not influence the time 36) The following are the main steps in the generation of necessary for a nerve impulse to be transmitted? an action potential. A) diameter of the axon 1. Sodium channels are inactivated. B) whether or not the impulse begins in the CNS 2. Voltage-gated potassium channels open and C) presence or absence of a myelin sheath potassium moves out of the cell, initiating D) length of the axon repolarization. E) presence or absence of nodes 3. Sodium channels regain their normal properties. 4. A graded depolarization brings an area of an excitable membrane to threshold. 42) Which of the following types of nerve fiber possesses 5. A temporary hyperpolarization occurs. the fastest speed of impulse propagation? 6. Sodium channel activation occurs. A) type A B) type B C) type C D) type D E) type E 7. Sodium ions enter the cell and depolarization occurs. 43) Which of the following comparisons between The proper sequence of these events is neurons and muscle tissue is false? A) 4, 6, 7, 1, 2, 3, 5. A) Muscle fibers conduct action potentials only by B) 6, 7, 4, 1, 2, 3, 5. continuous propagation. C) 2, 4, 6, 7, 1, 3, 5. B) Action potentials are briefer in muscle fibers. D) 4, 6, 7, 3, 2, 5, 1. C) Resting potentials are greater in muscle fibers. E) 4, 2, 5, 6, 7, 3, 1. D) Action potentials last longer in muscle fibers. 37) The sodium-potassium ion exchange pump E) Muscle fibers conduct action potentials at slow A) depends on a hydrogen gradient for energy. speeds. B) transports potassium ions out of the cell during 44) Which type of synapse is most common in the repolarization. nervous system? C) transports sodium ions into the cell during A) mechanical depolarization. B) processing D) moves sodium and potassium opposite to the C) radiative direction of their electrochemical gradients. D) electrical E) chemical B) the frequency of neurotransmitter release. 45) The ion that triggers the release of acetylcholine into C) the nature of the neurotransmitter. the synaptic cleft is D) the characteristics of the receptors. A) sodium. E) all of the above B) magnesium. 51) Which of the following is the most important C) chloride. excitatory neurotransmitter in the brain? D) potassium. A) serotonin E) calcium. B) glutamate 46) Cholinergic synapses release the neurotransmitter C) glycine A) norepinephrine. D) gamma aminobutyric acid B) adrenalin. E) noradrenaline C) acetylcholine. 52) Which of the following is not a possible drug effect D) GABA. on synaptic function? E) serotonin. A) block neurotransmitter binding to receptors 47) The following are the steps involved in transmission B) interfere with neurotransmitter synthesis at a cholinergic synapse. C) change the type of receptor found in the postsynaptic 1. Chemically gated sodium channels on the membrane postsynaptic membrane are activated. D) interfere with neurotransmitter reuptake 2. Calcium ions enter the synaptic knob. E) prevent neurotransmitter inactivation 3. Acetylcholinesterase hydrolyzes acetylcholine. 53) The site in the neuron where EPSPs and IPSPs are 4. An action potential depolarizes the synaptic knob at integrated is the the presynaptic membrane. A) dendritic membrane. 5. The synaptic knob reabsorbs choline. B) electrical synapse. 6. Acetylcholine is released from storage vesicles by C) synaptic knob. exocytosis. D) chemical synapse. 7. Acetylcholine binds to receptors on the postsynaptic E) axon hillock. membrane. 54) EPSPs (excitatory postsynaptic potentials) occur 8. Calcium ions are removed from the cytoplasm of the when synaptic knob. A) chloride ions enter a cell. The correct sequence for these events is B) hyperpolarizations occur. A) 4, 2, 6, 7, 1, 8, 3, 5. C) more calcium ions than usual leak out of a cell. B) 2, 4, 6, 7, 1, 8, 3, 5. D) more potassium ions than usual leak out of a cell. C) 2, 5, 4, 6, 7, 1, 8, 3. E) extra sodium ions enter a cell. D) 6, 4, 2, 7, 1, 8, 3, 5. 55) IPSPs (inhibitory postsynaptic potentials) E) 4, 2, 6, 7, 8, 5, 3, 1. A) are local hyperpolarizations. 48) Adrenergic synapses release the neurotransmitter B) block the efflux of potassium ions. A) acetylcholine. C) block the efflux of calcium ions. B) GABA. D) are local depolarizations. C) serotonin. E) increase membrane permeability to sodium ions. D) norepinephrine. 56) When a second EPSP arrives at a single synapse E) dopamine. before the effects of the first have disappeared, what occurs? A) spatial summation B) temporal summation C) hyperpolarization D) decrease in speed of impulse transmission E) inhibition of the impulse 49) If the chemically gated sodium channels in the 57) Summation that results from the cumulative effect of postsynaptic membrane were completely blocked, multiple synapses at multiple places on the neuron is A) release of neurotransmitter would stop. designated B) synaptic transmission would fail. A) inhibition of the impulse. C) smaller action potentials would result. B) impulse transmission. D) both A and B C) temporal summation. E) A, B, and C D) hyperpolarization. 50) The effect that a neurotransmitter has on the E) spatial summation. postsynaptic membrane depends on 58) After acetylcholinesterase acts, the synaptic knob A) the quantity of neurotransmitters released. A) reabsorbs the acetate. B) reabsorbs the acetylcholine. A) neurotubules C) reabsorbs the choline. B) mitochondria D) all of the above C) neurofibrils E) both B and C D) vesicles 59) Active neurons need ATP to support which of the E) all of the above following? A) the synthesis of neurotransmitter molecules 67) ________ neurons are small and have no anatomical B) the movement of materials to the soma by axoplasmic features that distinguish dendrites from axons. transport A) Bipolar C) the movement of materials from the soma by B) Anaxonic axoplasmic transport C) Multipolar D) the recovery from action potentials D) Unipolar E) all of the above E) none of the above 60) The efferent division of the peripheral nervous 68) ________ neurons are short, with a cell body between system innervates: dendrite and axon, and occur in special sense organs. A) glandular cells A) Bipolar B) smooth muscle cells B) Multipolar C) skeletal muscle cells C) Anaxonic D) heart muscle cells D) Unipolar E) all of the above E) none of the above 61) Integral membrane proteins that connect electrical 69) In a(n) ________ neuron, the dendrites and axon are synapses are called continuous or fused. A) connexons. A) anaxonic B) desmosomes. B) bipolar C) receptors. C) multipolar D) synapsins. D) unipolar E) sodium channels. E) none of the above 62) The same ________ can have different effects 70) ________ neurons are the most common class in the depending on the properties of the ________. CNS. A) neurotransmitter; receptor A) Multipolar B) hormone; neurotransmitter B) Anaxonic C) receptor; neurotransmitter C) Bipolar D) propagation; neurotransmitter D) Unipolar E) substrate; receptor E) none of the above 63) Deteriorating changes in the distal segment of an 71) ________ neurons form the afferent division of the axon as a result of a break between it and the soma is PNS. called ________ degeneration. A) Visceral sensory A) peripheral B) Neural sensory B) Wallerian C) Sensory C) conduction D) Somatic sensory D) neural E) none of the above E) central 72) ________ are the most numerous type of neuron in 64) Which of the following is a function of neuroglia? the CNS. A) regulate the composition of interstitial fluid A) Unipolar neurons B) produce cerebrospinal fluid B) Sensory neurons C) act as phagocytes C) Bipolar neurons D) provide a supportive framework D) Interneurons E) all of the above E) Motor neurons 65) The cytoskeleton of the perikaryon contains which of 73) Which of the following are types of neuroglia? the following? A) oligodendrocytes A) neurofibrils B) microglia B) neurofilaments C) astrocytes C) neurotubules D) ependymal cells D) B and C only E) all of the above E) A, B, and C 74) ________ account for roughly half of the volume of 66) The axoplasm of the axon contains which of the the nervous system. following? A) Synapses B) Axons B) leak channels. C) Dendrites C) chemically gated channels. D) Neuroglia D) active channels. E) Efferent fibers E) both B and D 75) Ions can move across the plasma membrane in which 83) ________ open or close in response to binding of the following ways? specific molecules. A) through passive or leak channels A) Voltage-gated channels B) through voltage-gated channels as in the action B) Chemically gated channels potential C) Activated channels C) through chemically-gated channels as in D) Leak channels neuromuscular transmission E) both C and D D) by ATP-dependent ion pumps like the sodium- 84) ________ channels open or close in response to potassium exchange pump physical distortion of the membrane surface. E) all of the above A) Chemically gated 76) Which of the following are properties of B) Mechanically gated cerebrospinal fluid? C) Active A) fills the brain ventricles D) Voltage-gated B) transports nutrients E) Leak C) circulates continuously D) surrounds the brain and spinal cord E) all of the above 77) The function of the astrocytes in the CNS includes which of the following? 85) Any stimulus that opens ________ ion channel will A) maintaining the blood-brain barrier produce a graded potential. B) adjusting the composition of the interstitial fluid A) a chemically gated C) repairing damaged neural tissue B) a mechanically gated D) guiding neuron development C) a voltage-gated E) all of the above D) a sodium 78) The largest and most numerous neuroglia in the CNS E) any of the above are the 86) Type ________ fibers have the largest diameter A) astrocytes. axons. B) microglia. A) C B) S C) F D) B E) A C) oligodendrocytes. 87) Sensory information from skeletal muscles travels D) ependymal cells. over ________ fibers. E) none of the above A) type A B) type B C) type C D) type D E) type E 79) The smallest neuroglia of the CNS are the 88) Which of the following statements about the action A) microglia. potential is false? B) oligodendrocytes. A) In the after-hyperpolarization phase, membrane C) ependymal cells. potential approaches the potassium equilibrium D) astrocytes. potential. E) none of the above B) During the repolarization phase, sodium channels 80) Raising the potassium ion concentration in the close and potassium channels open. extracellular fluid surrounding a nerve cell will have C) The rapid depolarization phase is caused by the entry which of potassium ions. effect? D) During the depolarization phase, membrane potential A) depolarize it becomes positive. B) increase the magnitude of the potassium equilibrium E) None of these statements is false all are true. potential 89) For which of the following functions do active C) hyperpolarize it neurons require a supply of ATP? D) decrease the magnitude of the potassium equilibrium A) axoplasmic transport potential B) powering the sodium-potassium exchange pump E) both A and D C) synthesis and reuptake of neurotransmitters 81) The equilibrium potential for potassium ion occurs at D) all of the above approximately E) A and C only A) +66 mV. B) 0 mV. C) —70 mV. D) —90 mV. E) C or D 90) When pressure is applied to neural tissue, all these 82) Ion channels that are always open are known as effects are possible, except A) voltage-gated channels. A) the axon becomes inexcitable. B) action potentials are generated spontaneously. D) astrocytes form a capsule around neurons. C) a decrease in blood flow. E) ependymal cells restrict the flow of interstitial fluid D) neurons are triggered to divide. between the capillaries and the neurons. E) glial cells degenerate. 97) Extensive damage to oligodendrocytes in the CNS 91) In the peripheral nervous system, Schwann cells could result in participate in the repair of damaged nerves by A) inability to produce scar tissue at the site of an injury. A) regenerating cell bodies for the neurons. B) loss of the structural framework of the brain. B) producing more satellite cells that fuse to form new C) loss of sensation and motor control. axons. D) a breakdown of the blood-brain barrier. C) forming a cellular cord that directs axonal regrowth. E) decreased production of cerebrospinal fluid. D) producing new axons. 98) Damage to ependymal cells would most likely affect E) clearing away cellular debris. the 92) Voltage-gated sodium channels have both an A) formation of cerebrospinal fluid. activation gate and a(n) ________ gate. B) formation of ganglia. A) inactivation C) transport of neurotransmitters within axons. B) ion D) formation of myelin sheaths. C) threshold E) repair of axons. D) repolarization 99) If the permeability of a resting axon to sodium ion E) swinging increases, 93) Most CNS neurons lack centrioles. This observation A) the membrane potential will depolarize. explains B) the membrane potential will hyperpolarize. A) the ability of neurons to generate an action potential. C) inward movement of sodium ion will increase. B) the ability of neurons to communicate with each D) outward movement of sodium ion will decrease. other. E) both A and C C) why CNS neurons cannot regenerate. 100) Graded potentials D) the ability of neurons to produce a resting potential. A) may be either a depolarization or a E) why CNS neurons grow such long axons. hyperpolarization. B) are often all-or-none. C) produce an effect that spreads actively across the membrane surface. 94) Each of the following is an example of a D) produce an effect that increases with distance from neuroeffector junction, except the junction between a the point of stimulation. neuron and a(n) E) cause repolarization. A) nerve cell. B) smooth muscle cell. C) skeletal muscle cell. D) endocrine gland cell. E) exocrine gland cell. 95) How does blocking retrograde axoplasmic transport 101) If the potassium permeability of a resting neuron in an axon affect the activity of a neuron? increases above the resting permeability, what effect will A) The neuron becomes unable to produce action this have on the transmembrane potential? potentials. A) There will be almost no effect on transmembrane B) The neuron becomes unable to produce potential. neurotransmitters. B) The membrane will become depolarized. C) The soma becomes unable to export products to the C) The inside of the membrane will become more synaptic knobs. negative. D) The neuron becomes unable to depolarize when D) The inside of the membrane will become more stimulated. positive. E) The soma becomes unable to respond to changes in E) both B and D the distal end of the axon. 102) If the sodium-potassium pumps in the plasma 96) Many medications introduced into the bloodstream membrane fail to function, all of the following occur, cannot directly affect the neurons of the CNS because except A) the endothelium of CNS capillaries forms a blood- A) the neuron will slowly depolarize. brain barrier. B) the membrane will slowly lose its capacity to generate B) oligodendrocytes form a continuous myelin sheath action potentials. around the axons. C) the intracellular concentration of sodium ions will C) the neurolemma is impermeable to most molecules. increase. D) the inside of the membrane will have a resting remaining open longer. potential that is more positive than normal. B) blockage of calcium channels in the presynaptic E) the intracellular concentration of potassium ions will membrane. increase. C) increased extracellular concentration of potassium 103) How would the absolute refractory period be ion. affected if voltage-regulated sodium channels failed to D) temporal summation. inactivate? E) increased extracellular concentration of sodium ion. A) It would be basically unaffected. 109) After a stroke, what type of glial cell accumulates B) It would last indefinitely. within the affected brain region? C) It would be much briefer. A) oligodendrocytes 104) In which of the following would the rate of impulse B) satellite cells conduction be the greatest? C) ependymal cells A) a nonmyelinated fiber of 10-μm diameter D) microglia B) a myelinated fiber of 1-μm diameter E) astrocytes C) a nonmyelinated fiber of 20-μm diameter 110) Puffer fish poison blocks voltage-gated sodium D) a myelinated fiber of 10-μm diameter channels like a cork. What effect would this neurotoxin E) the same in all because of the all-or-none principle have 105) Which of the following is true about threshold for on the function of neurons? an action potential A) Action potentials would lack a repolarization phase. A) It is more positive than the resting potential. B) The axon would be unable to generate action B) Voltage-gated potassium channels begin to close. potentials. C) Voltage-gated sodium channels begin to open. C) Neurons would depolarize more rapidly. D) A and C only D) The absolute refractory period would be shorter than E) A, B, and C normal. 106) When cholinergic receptors are stimulated, E) None, because the chemically gated sodium channels A) sodium ions enter the postsynaptic neuron. would still function. B) chloride ions leave the postsynaptic neuron. 111) Opioids relieve pain by blocking the release of C) sodium ions leave the postsynaptic neuron. A) substance P. D) chloride ions enter the postsynaptic neuron. B) substance Q. E) both B and D C) substance X. 107) If the axon terminal of a motor neuron suddenly D) substance O. became permeable to calcium ion, E) none of the above A) the neuron will become unable to stimulate the 112) Which of the following is a recognized class of muscle cell. opioid neuromodulators? B) the neuron will fire an action potential. A) endomorphins C) the motor end plate will be depolarized. B) dynorphins D) the motor end plate will be hyperpolarized. C) endorphins E) neurotransmitter release will be blocked. D) enkephalins 108) Presynaptic facilitation by serotonin is caused by E) all of the above A) calcium channels in the presynaptic membrane Figure 12-1 The Neuron Use Figure 12-1 to answer the following questions: 113) The structures labeled "1" are dendrites. Their 115) Which type of membrane channels are found at membranes contain numerous chemically gated ion label "3"? channels. A) voltage-gated Na+ channels A) Both statements are true and relate to synaptic B) voltage-gated K+ channels transmission. C) chemically gated Na+ and K+ channels B) Both statements are true. D) voltage-gated Ca2+ channels C) The first statement is false but the second statement is E) both A and B true. 116) Which part of the neuron can conduct an action D) Both statements are false. potential? E) The first statement is true but the second statement is A) 1 B) 1 and 2 C) 2 and 3 D) 3 and 4 E) 3, 4, and 5 false. 18 114) The structure labeled "2" is a 117) Identify the structure labeled "5." A) soma. A) telodendria B) Nissl body. B) dendritic spines C) initial segment. C) axosomata D) perikaryon. D) synaptic terminals E) dendrite. E) axons Figure 12-2 The Nerve Action Potential Use Figure 12-2 to answer the following questions: 118) Which area of the graph shows when passive sudden inrush of sodium ions? depolarization is occurring? A) 1 B) 2 C) 3 D) 4 A) 1 B) 2 C) 3 D) 4 120) Which area of the graph shows when membrane 119) Which area of the graph occurs when there is a potential approaches the potassium equilibrium potential? A) 1 B) 2 C) 3 D) 4 A) 1 B) 2 C) 3 D) 4 122) When is the neuron in the refractory period? 121) Which point of the graph shows when potassium A) 1 B) 2 C) 3 D) 4 ion outflow exceeds sodium ion inflow? SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. 123) The nervous tissue outside of the central nervous system composes the ________ nervous system. 124) The ________ division of the peripheral nervous system brings sensory information to the central nervous system. 19 125) The ________ division carries motor commands to muscles and glands. 126) The ________ nervous system provides involuntary regulation of smooth muscle, cardiac muscle, and glandular activity. 127) The plasma membrane of an axon is called the ________. 128) The basic functional unit of the nervous system is the ________. 129) The tiny gaps between adjacent Schwann cells are called ________. 130) A movement of charges in response to a potential difference is called a ________. 131) The separation of plus and negative charges across the membrane creates a ________ difference, or voltage. 132) The sum of the electrical and chemical forces acting on an ion is known as its ________. 133) The minimum stimulus required to trigger an action potential is known as the ________. 134) The ________ principle states that the size and speed of the action potential are independent of the stimulus strength. 135) The period during which an excitable membrane cannot respond to further stimulation is the ________. 136) The period during which an excitable membrane can respond again, but only if the stimulus is greater than the threshold stimulus, is the ________. 137) An action potential traveling along an axon is also called a(n) ________. 138) At a(n) ________ synapse, a neurotransmitter is released to stimulate the postsynaptic membrane. 139) In a(n) ________ synapse, current flows directly between cells. 140) Compounds that alter the rate of neurotransmitter release by the presynaptic neuron or change the postsynaptic cell's response to neurotransmitters are called ________. 141) The buildup of depolarization when EPSPs arrive in rapid succession is called ________ summation. 142) The buildup of depolarization when EPSPs arrive at several places on the neuron is called ________ summation. 143) ________ carry sensory information to the CNS. 144) ________ carry motor information to peripheral effectors. 145) ________ are nerves that connect to the spinal cord. 146) ________ are nerves that connect to the brain. 147) Match the system with its components. 1. central nervous system 2. peripheral nervous system 3. somatic nervous system 4. autonomic nervous system A) includes all neural tissue outside the CNS B) includes the spinal cord and brain C) controls visceral effectors D) controls skeletal muscle contractions 148) Match the sensory receptor with its function. 1. interoceptors 2. exteroceptors 3. proprioceptors A) monitor the position and movement of skeletal muscles and joints B) provide sensations of taste, deep pressure, and pain C) provide information about the external environment 149) Match the membrane potential with its example. 1. repolarization 2. hyperpolarization 3. depolarization A) an increase from -70 to -80 mV B) changes from rest to a more positive value C) return to resting potential after depolarization 150) ________ monitor the digestive, respiratory, cardiovascular, urinary, and reproductive systems. 151) Products from the soma of a neuron are transported to the synaptic terminals by ________ axoplasmic transport. 152) A change in the conditions in the synaptic knob can influence the soma as a result of ________ axoplasmic transport. 153) Regions of the CNS with an abundance of myelinated axons constitute the ________ matter. 154) Regions of the CNS where neuron cell bodies dominate constitute the ________ matter. 155) Neuron cell bodies in the PNS are clustered together in masses called ________. 156) ________ provide information about the external environment. 157) ________ monitor the position of skeletal muscles and joints. 158) ________ monitor the internal environment. 159) The basic functional unit of the nervous system are cells called ________. 160) During fetal development and early childhood, the free surface of ependymal cells is covered with ________. 161) The presence of ________ dramatically increases the speed at which an action potential moves along an axon. 162) The sensory loss and muscle weakness associated with multiple sclerosis are a consequence of ________. 163) A shift of the resting transmembrane potential toward 0 mV is called ________. 164) The period from when an action potential begins until normal excitability returns is known as the ________period. 165) Most neurons lack ________ and so are permanently blocked from undergoing cell division. ESSAY. Write your answer in the space provided or on a separate sheet of paper. 166) Rabies is caused by a virus that attacks the central nervous system. The virus is normally introduced by an animal bite that breaks the surface of the skin. Since the virus is not motile, how does it travel to the central nervous system? 167) The myelination of central and peripheral axons occurs rapidly through the first few years of life. How can this developmental process explain the improved motor abilities of infants and toddlers? 168) A drug that blocks ATP production is introduced into an isolated axon preparation. The axon is then repeatedly stimulated, and recordings are made of the response. What effects would you expect to observe?