【文章內(nèi)容簡介】 ell membrane potential must reach a threshold value of … ~ 55mV ? When this threshold is reached, the voltagegated Na+ channels open, allowing more Na+ to diffuse rapidly into the cell. – DEPOLARIZATION TIME Membrane Voltage (mV) 70 55 0 30 22 CQ6: At the peak of the action potential, Na+ voltagegated channels close, and K+ voltagegated channels open in response to positive membrane potential. To return the cell to its negative resting potential quickly: A. K+ will diffuse along its concentration gradient INTO the cell. B. K+ will diffuse along its concentration gradient OUT of the cell. C. Na+ will reverse its direction of diffusion OUT of the cell. D. The sodiumpotassium pump will move Na+ OUT of the cell and K+ INTO the cell. E. None of the above would return the cell to its negative resting potential quickly. TIME Membrane Voltage (mV) 70 55 0 30 23 CQ7: Dr. Westwood ate a meal of pufferfish and rice. As a result, he was a victim of pufferfish poisoning that caused his lifethreatening symptoms of numbness, paralysis, irregular heartbeat, and difficulty breathing. Tetrodotoxin (TXX), found in pufferfish flesh, is a molecule that: A. Causes the flesh of pufferfish to go bad. B. Causes an incurable illness in humans. C. Blocks voltagegated sodium ion channels. D. Blocks neurotoxins. E. Affects the immune system. 24 CQ8: If tetrodotoxin (TXX) blocks voltagegated sodium ion channels, which part of the action potential would be impacted? A. Part A B. Part B C. Part C D. Part D E. Part E TIME Membrane Voltage (mV) 70 55 0 30 A B C D E 25 CQ9: Dr. Westwood experienced numbness after eating the pufferfish meal because TXX causes: A. Motor neurons to fire continuously, overloading the brain with signals, resulting in numbness. B. Motor neurons to stop firing, preventing munication with the brain, resulting in numbness. C. Sensory neurons to stop firing preventing munication with the brain, resulting in numbness. D. Sensory neurons to fire continuously, overloading the brain with signals, resulting in numbness. E. None of the above explain why Dr. Westwood experienced numbness after his pufferfish meal. 26 CQ10: Why did Dr. Westwood experience paralysis after eating the pufferfish meal? A. TXX causes motor neurons to fire continuously, overloading the brain with signals, resulting in paralysis. B. TXX causes motor neurons to stop firing, preventing munication with the muscles, resulting in paralysis. C. TXX causes sensory neurons to stop firing preventing munication with the brain, resulting in paralysis. D. TXX causes sensory neurons to fire continuously, overloading the brain with signals, resulting in paralysis. E. None of the above explain why Dr. Westwood experienced numbness after his pufferfish meal. 27 After recovering from his TTX poisoning, Dr. Marshall Westwood took a vacation. An avid birder, he went to Papua New Guinea with Bill Whitlatch, an ornithologist and friend. 28 Three days into their trip, Bill ted a bird with an orange body and black wings and head. Dr. Westwood was