MUSCLE
CARDIAC MUSCLE
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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repolarization
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early rapid repolarization
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depolarization
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plateau
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Detailed explanation-1: -Phase zero is the phase of depolarization. This phase starts when the membrane potential reaches-40 mV, the threshold potential for pacemaker cells. There is the opening of voltage-gated Ca2+ channels on reaching the threshold, causing the influx of Ca2+ ions.
Detailed explanation-2: -The action potential in ventricular cardiomyocytes begins with a rapid upstroke (phase 0) caused by the regenerative opening of fast Na+ channels.
Detailed explanation-3: -The cardiac transmembrane action potential consists of five phases:phase 0, upstroke or rapid depolarization; phase 1, early rapid repolarization; phase 2, plateau; phase 3, final rapid repolarization; andphase 4, resting membrane potential and diastolic depolarization (Fig.