MEDICAL
HEART AND PERICARDIUM
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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phase 0 (Depolarization)
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Phase 1 (Brief Repolarization)
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Phase 2 ( Plateau)
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Phase 3 (Repolariation)
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Detailed explanation-1: -In these cells, phase 4 is also known as the pacemaker potential. During this phase, the membrane potential slowly becomes more positive, until it reaches a set value (around-40 mV; known as the threshold potential) or until it is depolarized by another action potential, coming from a neighboring cell.
Detailed explanation-2: -Contractile cells have an action potential with an extended plateau phase that results in an extended refractory period to allow complete contraction for the heart to pump blood effectively.
Detailed explanation-3: -Once the membrane potential starts to repolarize, the K+ channels begin to close because they sense the voltage. However, even though the membrane potential has returned to-60 mV, some of the voltage-dependent K+ channels remain open. Thus, the membrane potential will be more negative than it was initially.