Exam 4 Bio Chapter 43/44 – Flashcards
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1. In vertebrates, the ______ nervous system is composed of the brain and the spinal cord. A. peripheral B. central C. somatic D. autonomic E. sympathetic
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B. central
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2. What are the branched extensions of a neuron that receive signals called? A. axons B. cell bodies C. dendrites D. oligodendrocytes E. synapses
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C. dendrites
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3. What is the elongated extension of a neuron that nerve impulses travel along? A. axon B. cell body C. dendrite D. oligodendrocyte E. synapse
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A. axon
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4. What are examples of cells that support neurons both structurally and functionally? A. dendrites and nodes of Ranvier B. neuroglia and nodes of Ranvier C. Schwann cells and dendrites D. dendrites, nodes of Ranvier, and neuroglia E. Schwann cells, oligodendrocytes, and other neuroglia
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E. Schwann cells, oligodendrocytes, and other neuroglia
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5. You dissect the brain of a mutant mouse and find that parts of the "white matter" look gray. What is a likely cause? A. defects in myelination B. peripheral nerve damage C. oversized dendrites D. excess myelination E. excess neuronal proliferation
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A. defects in myelination
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6. You are studying a gene which, when mutant, causes oligodendrocytes to enwrap shorter sections of axon, so that nodes of Ranvier are more closely spaced. What is the likely effect on nerve impulses? A. They will travel faster. B. They will travel slower. C. They will increase in amplitude. D. They will decrease in amplitude. E. They will travel laterally across connected axons.
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B. They will travel slower.
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7. What other cells should you examine for effects from this mutant gene? A. prefrontal neurons B. gustatory neurons C. cholinergic neurons D. Schwann cells
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D. Schwann cells
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8. Rapid inward diffusion of Na+ produces a dramatic change in membrane potential. What is this event called? A. hyperpolarization B. excitatory postsynaptic potential C. saltatory conduction D. monosynaptic reflex E. depolarization
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E. depolarization
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9. Nerve impulses are electrical signals produced by which structure? A. lipid sheath of Schwann cell B. plasma membrane of neuron C. synapse D. neuromuscular junction
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B. plasma membrane of neuron
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10. The membrane of a resting neuron is most permeable to which of the following ions? A. Cl- B. Ca2+ C. Na+ D. K+ E. H+
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D. K+
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11. When neurons are not producing electrical signals, there is still a voltage difference across their membranes. What is this voltage called? A. channel-gate bias B. electrolyte voltage C. equilibrium potential D. resting potential E. ion current
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D. resting potential
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12. Which of the following characteristics are true for an action potential? I-A threshold potential must be exceeded for an action potential to occur. II-A stimulus either produces a full action potential or none at all. III-During the refractory period it is less likely that stimuli can produce another action potential. A. I only B. I and II C. II and III D. I and III E. I, II, and III
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E. I, II, and III
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13. What is the process in which impulses jump from node to node? A. facilitated transmission B. refractory action C. incomplete transfer D. repolarization E. saltatory conduction
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E. saltatory conduction
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16. What determines the direction of the voltage change that occurs at the postsynaptic membrane? A. the type of neurotransmitter B. the type of second messenger system used C. the type(s) of ions that travel through opened channels D. the number of ion channels on the postsynaptic membrane
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C. the type(s) of ions that travel through opened channels
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17. At myelinated areas of the axon (i.e. between nodes of Ranvier), which of the following statements is true? A. There is an increased number of voltage-gated sodium channels. B. There is increased resistance across the membrane. C. There is increased capacitance across the membrane. D. There is increased transport of potassium across the membrane.
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B. There is increased resistance across the membrane.
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18. Which ion channel is primarily responsible for the action potential? A. the voltage-gated sodium channel B. the voltage-gated potassium channel C. the ligand-gated sodium channel D. the ligand-gated potassium channel E. the non-gated sodium channel
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A. the voltage-gated sodium channel
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19. What diffuses across the narrow synaptic cleft between the presynaptic axon and the postsynaptic cell to transmit a nerve impulse? A. neurotransmitter B. electrical impulse C. Na+ ion D. vesicle E. action potential
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A. neurotransmitter
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20. Which neurotransmitter is released from a motor neuron at the neuromuscular junction? A. acetylcholine B. GABA C. ephinephrine D. dopamine E. serotonin
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A. acetylcholine
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21. When acetylcholine stimulates the opening of ligand-gated ion channels on a postsynaptic cell, what is this event called? A. neuromuscular junction B. temporal summation C. inhibitory postsynaptic potential (IPSP) D. excitatory postsynaptic potential (EPSP) E. synaptic integration
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D. excitatory postsynaptic potential (EPSP)
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22. What is the name for the gap into which neurotransmitters are released? A. gap junction B. synaptic cleft C. postsynaptic membrane D. presynaptic membrane E. impulse channel
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B. synaptic cleft
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23. Place the following events that occur at the vertebrate neuromuscular junction in the correct order. I-Depolarization of the muscle fiber membrane. II-Generation of an action potential in the neuron. III-Stimulation of Ca2+ entry into the neuron. IV-Release of acetylcholine into the synapse. A. I, II, III, IV B. III, II, IV, I C. I, III, IV, II D. IV, II,III, I E. II, III, IV, I
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E. II, III, IV, I
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24. Which of the following are example of biogenic amines? A. epinephrine and endorphins B. GABA and serotonin C. epinephrine, dopamine, and GABA D. epinephrine, dopamine, and serotonin E. epinephrine, norepinephrine, dopamine, and serotonin
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E. epinephrine, norepinephrine, dopamine, and serotonin
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25. Place the following events involved in drug addiction in the correct sequence. I-The synapse becomes less sensitive, and normal function can only continue in the presence of the drug. II-CNS responds to increased firing by decreasing the number of drug receptors on the cell membrane. III-Drug molecule prevents receptor endocytosis and causes overstimulation of the postsynaptic cell. A. I, II, III B. III, II, I C. II, III, I D. III, I, II
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B. III, II, I
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26. Which of the following drugs has been discovered to bind to acetylcholine receptors? A. serotonin reuptake inhibitors B. thorazine C. cocaine D. codeine E. nicotine
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E. nicotine
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27. The hippocampus, amygdala, and hypothalamus are the major components of the ______ system. A. sympathetic B. reflex C. parasympathetic D. limbic E. autonomic
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D. limbic
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28. The spinal cord is enclosed by the vertebral column and layers of protective membranes. What are these membranes called? A. neural net B. white matter C. dorsal root D. meninges E. viscera
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D. meninges
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29. Damage to the substantia nigra, a specific region of the basal ganglia, can produce the resting muscle tremors characteristic of what disease? A. epilepsy B. Parkinson disease C. seizures D. Alzheimer disease E. insomnia
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B. Parkinson disease
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30. A region of the brain receives both sensory information from ascending nerve tracts and motor commands from the cortex and cerebellum. This region plays an important role in motor control. Which region is it? A. basal ganglia B. pituitary gland C. parietal lobe D. thalamus E. medulla oblongata
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A. basal ganglia
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31. Which area of the cerebral cortex is important for the formulation of thoughts into speech? A. Broca's area B. the pons C. the medulla oblongata D. Wernicke's area E. the cerebellum
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D. Wernicke's area
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32. Which animal phylum lacks a network of nerve cells for gathering information from the environment? A. Porifera - sponges B. Cnidaria - jellyfish, sea anenomes C. Platyhelminthes -- flatworms D. Nematoda - roundworms E. Mollusca - octopus, squid, clams, snails, and other mollusks
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A. Porifera - sponges
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33. In early vertebrates, which component of the brain was devoted largely to coordinating motor reflexes? A. thalamus B. forebrain C. midbrain D. hindbrain E. medulla oblongata
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D. hindbrain
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34. Where did information processing become increasingly centered in terrestrial vertebrates? A. thalamus B. forebrain C. midbrain D. hindbrain E. medulla oblongata
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B. forebrain
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35. Which region of the CNS listed below is NOT correctly paired with its function? A. Broca's and Wernicke's areas—language and speech B. Hypothalamus—regulates body temperature, appetite, and sleep C. Cerebellum—relay station for ascending and descending tracts D. Corpus callosum—connects the two brain hemispheres E. Hippocampus—memory
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C. Cerebellum—relay station for ascending and descending tracts
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36. Which major regions compose the contemporary vertebrate brain? A. rhombencephalon and prosencephalon only B. mesencephalon and rhombencephalon only C. prosencephalon and metencephalon only D. metencephalon, rhombencephalon, and prosencephalon E. rhombencephalon, mesencephalon, and prosencephalon
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E. rhombencephalon, mesencephalon, and prosencephalon
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37. Which of the following structures is NOT a component of the hindbrain? A. pons B. medulla oblongata C. ascending tracts D. cerebellum
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C. ascending tracts
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38. What is the primary function of the hindbrain in vertebrates? A. temperature control B. integration of sensory data C. memory storage D. control of the heartbeat E. coordination of motor reflexes
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E. coordination of motor reflexes
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39. Where do correlation, association, and learning occur in the brain? A. cerebellum B. corpus callosum C. medulla D. cerebrum E. pons
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D. cerebrum
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40. What is the site of primary sensory integration in the brain? A. medulla oblongata B. cerebrum C. cerebellum D. thalamus E. corpus callosum
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D. thalamus
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41. What region of the brain integrates visceral activities, body temperature, and heartbeat? A. medulla oblongata B. cerebrum C. hypothalamus D. thalamus E. corpus callosum
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C. hypothalamus
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42. Which of the following is NOT a feature of the limbic system? A. contains hippocampus and amygdala B. resides deep within the cerebrum C. responsible for emotional responses D. important in the formation and recall of memories E. part of the hypothalamus
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E. part of the hypothalamus
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43. The doctor informs you that your grandmother's stroke has caused damage to Wernicke's area. Which activity is likely to become more difficult for her? A. walking B. doing laundry C. having a conversation D. sleeping E. mathematical calculations
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C. having a conversation
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44. What additional factor is required to mediate the parasympathetic effects of acetylcholine? A. G-protein coupled receptor B. GABA C. AMPAR D. habituation E. synaptic integration
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A. G-protein coupled receptor
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45. Which division of the nervous system regulates the activity of smooth muscle, cardiac muscle, and glands? A. antagonistic nervous system B. autonomic nervous system C. sympathetic nervous system D. parasympathetic nervous system E. limbic nervous system
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B. autonomic nervous system
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46. Which of the following is not part of the peripheral nervous system? A. sympathetic division of the autonomic nervous system B. spinal cord C. parasympathetic division of the autonomic nervous system D. somatic nervous system E. sensory pathways
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B. spinal cord
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47. Which of the following targets is NOT regulated by the autonomic nervous system? A. skeletal muscles B. cardiac muscles C. glands of the body D. smooth muscles E. none of these
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A. skeletal muscles
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48. A cheetah is chasing a gazelle. What division of the vertebrate nervous system is regulating the stress response in both animals? A. somatic nervous system B. parasympathetic nervous system C. sympathetic nervous system D. parasymbiotic nervous system E. cerebral cortex
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C. sympathetic nervous system
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49. A cheetah has succeeded in catching a gazelle and has just finished feeding on the carcass. What division of the nervous system has increased in activity? A. somatic nervous system B. parasympathetic nervous system C. sympathetic nervous system D. parasymbiotic nervous system E. cerebral cortex
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B. parasympathetic nervous system
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50. For your birthday, you get a robot-building kit with three parts: 1) a set of gadgets for detecting sound, touch, and light, 2) a set of motors that can move mechanical parts, and 3) a microprocessor that can be programmed to respond to inputs according to predetermined rules. You build a robot car, and find it surprisingly lifelike as it navigates around the room. The three parts of the kit are analogous which parts of the human body? A. 1) autonomic nervous system, 2) somatic nervous system, 3) hypothalamus B. 1) sympathetic pathways, 2) parasympathetic pathways, 3) CNS C. 1) sensory pathways, 2) motor pathways and muscles, 3) CNS D. 1) motor pathways and muscles, 2) sensory pathways, 3) CNS
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C. 1) sensory pathways, 2) motor pathways and muscles, 3) CNS
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51. Dr. Robinson tapped on a patient's knee with the little hammer, but failed to see the usual kick of the patellar reflex. Since this reflex only involves a few neurons, what part of the nervous system might the doctor became concerned about? A. parasympathetic nervous system B. central nervous system C. sympathetic nervous system D. peripheral nervous system
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D. peripheral nervous system
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52. What do the the two sets of neurons damaged in Charcot-Marie-Tooth neuropathy comprise? A. peripheral nervous system B. autonomic nervous system C. somatic nervous system D. parasympathetic nervous system E. central nervous system
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A. peripheral nervous system
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53. Genetic studies have found that Charcot-Marie-Tooth may be caused by a mutation in the gene Mitofusin-2 (MFN2), which causes mitochondria to form large clumps. In what area of a neuron are these clumps most likely to cause a problem? A. axon B. synapse C. soma D. dendrite E. myelin
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A. axon
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54. Mutation of the peripheral myelin protein 22 (PMP22) gene, which causes demyelination of peripheral neurons, is a more common cause of Charcot-Marie-Tooth disease. In which cells is the function of the PMP22 gene important for normal function? A. Schwann cells B. fibroblasts C. peripheral neurons D. oligodendrocytes E. astrocytes
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A. Schwann cells
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55. How can mutations in different genes, functioning in different cells, lead to the same disease? From the following, choose the best responses to complete the sentences: "Physiological function requires that multiple cells work together. Various defects in different cells can impair function, leading to ___________ that are indistinguishable at the level of the whole organism. In Charcot-Marie-Tooth disease, motor nerve function can be impaired either by a problem within _______________ , or a problem in __________________ causing _______________." A. defects; somatic cells; oligodendrocytes; demyelination B. symptoms; motor neurons; Schwann cells; demyelination C. symptoms; sensory neurons; Schwann cells; fast axonal transport D. genotypes; dendrites; axons; fast axonal transport
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B. symptoms; motor neurons; Schwann cells; demyelination
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56. Subsequent to motor neuron degeneration in Charcot-Marie-Tooth disease, muscles begin to weaken and degenerate as well. What is the likely cause? A. Muscles will atrophy if they don't receive regular stimulation from motor neurons. B. Muscles require healthy Schwann cells for myelination as well. C. Muscles contain large numbers of mitochondria. D. Toxins leak out from the dying motor neurons onto the muscles.
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A. Muscles will atrophy if they don't receive regular stimulation from motor neurons.
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58. Your roommate is on an ultra-low fat diet to try to lose weight. Given what you know about structure of the nervous system, what advice would you give him? A. "You should drink large quantities of water, because the brain is mostly water." B. "Good for you! Losing weight by any means necessary can only help your brain." C. "You should eat some healthy unsaturated fats, like those found in fish, olive oil, and nuts, because your brain needs fatty acids to build the myelin sheaths around your axons." D. "You should eat trans fats, from donuts, because 'trans' is short for neurotransmission."
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C. "You should eat some healthy unsaturated fats, like those found in fish, olive oil, and nuts, because your brain needs fatty acids to build the myelin sheaths around your axons."
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60. Marathon runners are encouraged to stop at water stations along the course to stay hydrated. However, occasionally a runner drinks too much water and suffers from hyponatremia, or "water intoxication". While water itself is not toxic, drinking too much can upset ion balance in the extracellular space. Based on what you know about ions and nerve signaling, the levels of which important ion are most likely to be disrupted in hyponatremia? A. hydrogen B. potassium C. calcium D. sodium E. oxygen
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D. sodium
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61. You are an EMT on duty for the marathon. It is an extremely hot day. You say to your partner, "This weather is likely to _____________ the risk of hyponatremia, because ______________ will cause the athletes to lose ______________." A. increase, sweating, sodium B. decrease, urination, calcium C. decrease, shivering, potassium D. increase, panting, oxygen
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A. increase, sweating, sodium
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62. What branched structure allows a neuron to take in information from more than one source? A. node of Ranvier B. axon C. myelin D. dendrite
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D. dendrite
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63. What part of the neuron is responsible for most of the "house-keeping" tasks of the cell, including protein synthesis? A. myelin B. axon C. dendrite D. soma E. synapse
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D. soma
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64. If you were to compare the resting potential of a neuron to a battery, which way is the battery oriented? A. positive terminal outside of the cell, and negative terminal inside B. positive terminal inside of the cell, and negative terminal outside C. positive terminal pointing toward the axon, negative terminal toward the dendrite D. positive terminal pointing toward the dendrite, negative terminal toward the axon E. both terminals inside the cell soma
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A. positive terminal outside of the cell, and negative terminal inside
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65. How does the resting potential of a typical neuron compare to that of a 1.5V AA alkaline battery? A. A typical neuron has a resting potential of -70mV, or about 5% the voltage of the battery. B. A typical neuron has a resting potential of -70V, or about 50x the voltage of the battery. C. A typical neuron has a resting potential of +70mV, or about 5% the voltage of the battery. D. A typical neuron has a resting potential of +70V, or about 50x the voltage of the battery.
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A. A typical neuron has a resting potential of -70mV, or about 5% the voltage of the battery.
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66. To process information, postsynaptic neurons often add up simultaneous signals from several presynaptic neurons. Which structure and process allow them to do so? A. axons; temporal summation B. axons; spatial summation C. dendrites; temporal summation D. dendrites; spatial summation
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D. dendrites; spatial summation
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67. A neuron that engages in spatial summation acquires a mutation that causes dendrite overgrowth and promiscuous synapsing. What is the likely outcome? A. abnormally low frequency of action potentials B. summation will not occur C. abnormally high frequency of action potentials D. action potentials with stronger depolarization
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C. abnormally high frequency of action potentials
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69. What important resource do Schwann cells and oligodendrocytes provide to neurons? A. oxygen B. nutrients C. physical strength from microtubules D. Ca2+ currents E. insulating layers of membrane
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E. insulating layers of membrane
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70. A patient suffers from a disease that slows fatty acid synthesis. What is a likely impact of this disease on nervous system function? A. improved functioning due to a healthier weight B. insufficient myelination and slow axon conduction rate C. improved functioning due to better blood flow D. weaker action potentials with smaller depolarization
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B. insufficient myelination and slow axon conduction rate
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74. Is the resting membrane potential of a neuron closer to the equilibrium potential for K+ or Na+? A. K+ B. Na+ C. It is an average of the two.
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A. K+
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75. Three-quarters of the substantial amount of energy consumed by the brain is used to run a single molecular machine that maintains the resting potential of neurons. What is this machine called? A. K+ leak channel B. sodium-potassium pump C. acetylcholine receptor D. voltage-gated sodium channel E. voltage-gated calcium channel
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B. sodium-potassium pump
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76. A Hawaiian legend tells of a village that angered a shark god. In revenge, a "seaweed" began to grow in the tidepools that killed anyone who touched it. In fact, this "limu-make-o-Hana" -- a zoanthid cnidarian -- contains a palytoxin that locks the sodium-potassium pump open, allowing free flow of ions. If a villager suffers palytoxin poisoning, which way will the ions in his neurons flow? A. all ions will flow out B. potassium in, sodium out C. chloride and sodium out, potassium in D. sodium in, potassium out
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D. sodium in, potassium out
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77. What is the likely impact of this toxin on the resting potential of a neuron? A. The resting potential will require more energy to maintain. B. The resting potential will be more negative. C. It will destroy the ion gradients necessary for the resting potential. D. The resting potential will promote action potentials with a larger depolarization.
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C. It will destroy the ion gradients necessary for the resting potential.
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78. What is the likely impact of this toxin on action potentials? A. They will occur more frequently. B. They will be stronger and more unpredictable. C. Without ion gradients, action potentials are not possible. D. They will have longer refractory periods.
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C. Without ion gradients, action potentials are not possible.
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79. Since there is a larger concentration of potassium ions inside a neuron, why is the inside of the neuron negative (-70mV) relative to the outside? A. Potassium ions carry a negative charge. B. Negatively-charged proteins inside the cell counteract the charge of the potassium ions. C. The negative sign is just a historical convention. D. The high concentration of sodium ions outside the cell makes the inside negative by comparison.
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B. Negatively-charged proteins inside the cell counteract the charge of the potassium ions.
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80. Sodium ions are single atoms. Why can't they simply diffuse through the cell membrane's lipid bilayer? A. Since they are charged, ions can't cross the hydrophobic center of the membrane without a channel or pump. B. Sodium ions are covalently attached in groups of three, which are too large to diffuse easily. C. Ions do traverse the membrane easily, but the sodium-potassium pump moves them back across. D. Chelator proteins capture any ions that start to cross the bilayer.
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A. Since they are charged, ions can't cross the hydrophobic center of the membrane without a channel or pump.
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81. If K+ can exit the cell through leak channels, why don't they flow out until there are equal concentrations on both sides of the membrane? A. K+ can act as an enzymatic cofactor, and most K+ ions are bound to cellular enzymes. B. The leak channels allow a very slow leak that cannot keep pace with active import of K+ ions. C. Chelator molecules trap K+ on the inside of the membrane. D. The negative electrical potential inside the cell creates a force that holds the K+ ions in.
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D. The negative electrical potential inside the cell creates a force that holds the K+ ions in.
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82. The outside of a neuron is positively charged at resting potential. Why do K+ ions leave the cell when K+ channels open during an action potential? A. The diffusion gradient is the only factor that affects ion movement. B. K+ ions are actively pumped out by the sodium-potassium pump acting in reverse. C. Voltage-gated K+ channels open when membrane potential reaches +50 mV during the depolarization phase. The diffusion gradient and electrical force cooperate to drive K+ ions out of the cell. D. Negatively charged proteins leave the cell at the onset of the action potential.
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C. Voltage-gated K+ channels open when membrane potential reaches +50 mV during the depolarization phase. The diffusion gradient and electrical force cooperate to drive K+ ions out of the cell.
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83. The outside of a neuron is positively charged at resting potential. Why don't negative ions exit from the cell to normalize charge across the membrane? A. The positive charge outside the cell repels negative ions. B. There are no negative ions inside the cell. C. All of the chloride ions are already outside the cell. D. The negative charge inside the cell is carried by large proteins that cannot diffuse through the membrane.
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D. The negative charge inside the cell is carried by large proteins that cannot diffuse through the membrane.
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84. What does the Nernst equation allow us to do? A. Predict the function of a specific type of neuron. B. Calculate the equilibrium potential for an ion. C. Use a computer program to model axonal transmission. D. Calculate the magnitude of depolarization during an action potential.
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B. Calculate the equilibrium potential for an ion.
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87. What limits the frequency of action potentials? A. chloride ions B. spike amplitude C. nodes of Ranvier D. refractory period
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D. refractory period
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89. A patient of yours is injured in a car accident. The surgeon reports that while there is damage to the dorsal roots, the spinal cord and nerves otherwise appear intact. What functions would you expect to be affected in the patient? A. The patient may lose somatic function, but should retain autonomic function. B. The patient may lose motor function, but should retain sensory perception. C. The patient may lose some sensory perception, but should retain motor function. However, lack of proprioceptive input may make muscle control difficult. D. The patient may lose parasympathetic function, but should retain sympathetic function. They should avoid stressful situations.
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C. The patient may lose some sensory perception, but should retain motor function. However, lack of proprioceptive input may make muscle control difficult.
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91. Botulinum toxin, or "botox", has become popular for cosmetic surgery. The toxin prevents neurosecretory vesicles from docking at the plasma membrane and releasing neurotransmitter. How would this toxin affect the neuromuscular junction? A. Since ACh is not released, the muscles stay in a state of repeated contraction. B. Since ACh is not released, the muscles are not activated to contract and remain relaxed. C. Buildup of ACh causes promiscuous activation of all nearby sensory neurons. D. Buildup of ACh leaks back into the brain, creating a calming effect.
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B. Since ACh is not released, the muscles are not activated to contract and remain relaxed.
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92. You accidentally consume botulinum toxin by eating a contaminated can of sausages. What do you predict will be the most harmful physiological effect? A. slowed action potential conduction B. respiratory failure due to spastic paralysis (constant muscle contraction) C. respiratory failure due to flaccid paralysis (relaxed muscles) D. pupil dilation
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C. respiratory failure due to flaccid paralysis (relaxed muscles)
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93. Another toxin that also blocks neurotransmitter release is tetanus toxin; however, it primarily affects inhibitory interneurons of the spinal cord that negatively regulate motor neurons. Which would be symptoms of tetanus toxin poisoning? A. flaccid paralysis B. spastic paralysis C. slowed action potential conduction D. pupil dilation
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B. spastic paralysis
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94. In contrast to these toxins, strichnine acts postsynaptically, to block glycine from binding to receptors on motor neurons. Would you expect the symptoms of strichnine poisoning to be more similar to those of botulinum or tetanus toxin? A. tetanus toxin B. botulinum
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A. tetanus toxin
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95. How do temporal and spatial summation improve the processing power of the brain? A. Temporal summation allows circadian rhythms to regulate neuronal activity. Spatial summation allows latitude to regulate neuronal activity. B. Temporal summation allows a neuron to fire prolonged action potentials, and spatial summation allows a neuron to synapse onto new targets. C. Temporal and spatial summation both make the neuron more likely to fire action potentials. D. Temporal summation allows a neuron to recognize a persistent signal from a single presynaptic cell, and spatial summation allows a neuron to recognize a broad signal from multiple presynaptic cells.
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D. Temporal summation allows a neuron to recognize a persistent signal from a single presynaptic cell, and spatial summation allows a neuron to recognize a broad signal from multiple presynaptic cells.
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96. K+ channels in the heart do not have binding sites for ACh, yet parasympathetic release of ACh causes outward flux of K+ from heart cells. How does this occur? A. ACh triggers release of epinephrine from the adrenal glands, which in turn causes K+ flux out of heart cells. B. ACh binds to a G-protein coupled receptor on heart cells, and the G protein alpha subunit binds to a separate K+ channel and causes it to open. C. Parasympathetic neurons activate sympathetic neurons, which directly cause K+ flux from heart cells. D. ACh binds and activates a K+ pump on heart cells.
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B. ACh binds to a G-protein coupled receptor on heart cells, and the G protein alpha subunit binds to a separate K+ channel and causes it to open.
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97. What would happen if the G-protein coupled receptor in heart cells that binds to ACh had a mutation that caused it to bind more tightly to the G-protein alpha subunit? A. G-protein activation and K+ channel opening would happen more quickly. Heart rate may remain abnormally low, impairing response to stress. B. This would lead to K+ flow out of heart cells, causing increased hyperpolarization. C. G-protein activation and K+ channel opening would be slowed. Heart rate may remain abnormally high, especially following stress. D. This would lead to K+ flow into heart cells, causing increased depolarization.
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C. G-protein activation and K+ channel opening would be slowed. Heart rate may remain abnormally high, especially following stress.
