THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -The rapid depolarization period typically lasts 3–5 ms. Depolarization is followed by the plateau phase, in which membrane potential declines relatively slowly.

Detailed explanation-2: -SA node pacemaker cells depolarize at a rate of 60 to 100 per minute, while the AV node at 40 to 60 per minute. The pacemaker with the highest rate of depolarization takes over as the primary pacemaker.

Detailed explanation-3: -How much blood is pumped from each ventricle during the ventricular ejection phase? The long length of the cardiac action potential, at 200-300 msec, allows for:-a reduction in strength of the heart’s contraction.

Detailed explanation-4: -Cardiac action potentials have strikingly longer durations (200 to 400 msec) than either nerve or muscle (1 to 5 msec). The long plateau phase around 0 mV provides the sustained depolarization and contraction needed to empty the heart’s chambers.