Question

The heart keeps on beating throughout the life without fatigue because

• A. it contracts slowly
• B. it has a refractory period
• C. it can use lactic acid as an extra source of energy
• D. none of the above

Answer 1

The correct option is B it has a refractory period

The refractory is a period immediately following stimulation during which a nerve or muscle is unresponsive to further stimulation. A longer refractory period ensures that the heart cannot contract twice in a row too quickly. This allows the muscle to fully relax before it contracts again, giving the maximum amount of "pump" possible. If the heart were to contract again too soon, it may only be able to "pump" a fraction of that amount because it did not relax all the way. And this keeps the heart beating throughout the life without fatigue.