Test_04_5_Answr

Test_04_5_Answr - Test4&5; CBNS106; Lectures: 04 and 05...

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Test4&5; CBNS106; Lectures: 04 and 05 Page 1 of 7 Problem set for lecture 4 and 5: Action Potential Reading Assignment: Bear et al. Chapters 4 & 5 1. How does myelin help increase conduction velocity? Choose the correct option. A) It provides electrical insulation. B) It makes the membrane more excitable. C) It contains voltage-gated sodium channels. D) It increases axonal diameter. 2. What is the absolute refractory period? Choose the correct option. A) The period when the firing frequency is at about 1000 Hz. B) The time period of 1 msec after one action potential is initiated and before the next one is initiated. C) The period when it is difficult to initiate another action potential for several milliseconds due to sodium channel inactivation. D) The period when the membrane potential stays hyperpolarized until the voltage-gated potassium channels close. 3. The spike-initiation zone in most peripheral sensory neurons occurs near the sensory nerve endings. A) True B) False 4. The part of the neuron where an axon originates from the soma is called the ____. It is also called the spike-initiation zone. A) True B) False 5. What is meant by the action potential threshold? Choose the correct option. A) Critical level of depolarization required to trigger an action potential B) Critical level of hyperpolarization required to trigger an action potential C) The action potential threshold is the same as the generator potential D) Critical level at which electrical current is injected through a microelectrode 6. What property of the voltage-gated potassium channels allows K+ ions to pass? Choose the correct option. A) Two polypeptide subunits are synthesized when the membrane is depolarized, allowing the K+ ions to pass.
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Test4&5; CBNS106; Lectures: 04 and 05 Page 2 of 7 B) Depolarization causes the subunits to disintegrate so K+ ions can pass through the membrane. C) The voltage-gated potassium channels open when the polypeptide sub-units are disinhibited. D) Depolarization causes the four polypeptide subunits specific to the voltage-gated K+ channel to twist into a shape that allows the K+ ions to pass. 7. How does the sodium channel selectivity filter differentiate Na+ and K+ ions? Choose the correct option. A) K+ ions have the wrong charge. B) The K+ ions are stripped of all their water molecules but the Na+ ions are not. C) Sodium channel admits a Na+ water complex with the water serving as a molecular chaperone through the channel. D) K+ is excluded by voltage gating. 8. The movement of what ion is reflected in the rising phase of the action potential? Choose the correct option. A) Inward Na+ B) Outward K+ C) Outward Na+ D) Inward K+ 9. What type of channel is affected by tetrodotoxin (TTX)? Choose the correct option. A) K+ channels are blocked by TTX.
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This note was uploaded on 04/15/2008 for the course CBNS 106 taught by Professor Korzus during the Winter '08 term at UC Riverside.

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Test_04_5_Answr - Test4&5; CBNS106; Lectures: 04 and 05...

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