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A blockade of voltage sensitive na channels b

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A) Blockade of voltage-sensitive Na+ channelsB) Blockade of voltage-sensitive K+ channelsC) Blockade of Na-K “leak” channelsD) Replacement of the voltage-sensitive K+ channels with“slow” Ca++ channelsE) Replacement of the voltage-sensitive Na+ channels with“slow” Ca++ channels
51.Trace A represents a typical action potential recorded undercontrol conditions from a normal nerve cell in response to adepolarizing stimulus. Which of the following perturbationswould explain the conversion of the response shown in trace Ato the action potential shown in trace B?A) Blockade of voltage-sensitive Na+ channelsB) Blockade of voltage-sensitive K+ channelsC) Blockade of Na-K “leak” channelsD) Replacement of the voltage-sensitive K+ channels with“slow” Ca++ channelsE) Replacement of the voltage-sensitive Na+ channels with“slow” Ca++ Channels X
These so-called slow Ca++ channels have a slower inactivation rate,thereby lengthening the time during which they are open. This, inturn, delays the repolarization phase of the action potential,creating a “plateau” before the channels inactivate.
52.Which of the following perturbations would account forthe failure of the same stimulus to elicit an actionpotential in trace C?A) Blockade of voltage-sensitive Na+ channelsB) Blockade of voltage-sensitive K+ channelsC) Blockade of Na-K “leak” channelsD) Replacement of the voltage-sensitive K+ channelswith “slow” Ca++ channelsE) Replacement of the voltage-sensitive Na+ channelswith “slow” Ca++ channels
52.Which of the following perturbations would account forthe failure of the same stimulus to elicit an actionpotential in trace C?A) Blockade of voltage-sensitive Na+ channels XB) Blockade of voltage-sensitive K+ channelsC) Blockade of Na-K “leak” channelsD) Replacement of the voltage-sensitive K+ channelswith “slow” Ca++ channelsE) Replacement of the voltage-sensitive Na+ channelswith “slow” Ca++ channels
53.A 17-year-old soccer player suffered a fracture to the left tibia.After her lower leg has been in a cast for8 weeks, she issurprised to find that the left gastrocnemius muscle issignificantly smaller in circumference than it was before thefracture. What is the most likely explanation?A) Decrease in the number of individual muscle fibers in theleft gastrocnemiusB) Decrease in blood flow to the muscle caused byconstriction from the castC) Temporary reduction in actin and myosin protein synthesisD) Increase in glycolytic activity in the affected muscleE) Progressive denervation
53.A 17-year-old soccer player suffered a fracture to the left tibia. Afterher lower leg has been in a cast for8 weeks, she is surprised to findthat the left gastrocnemius muscle is significantly smaller incircumference than it was before the fracture. What is the most likelyexplanation?

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Term
Fall
Professor
Allen
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