Question

If the length of the absolute refractory period in cardiac muscle cells was the same as it is for skeletal muscle cells, ________. A) it would be much longer before cardiac cells could respond to a second stimulation B) contractions would last as long as the refractory period C) tetanic contractions might occur, which would stop the heart's pumping action D) pacemaker cells would cease to spontaneously depolarize

Answer 1

Answer:

C. tetanic contractions might occur, which would stop the heart's pumping action.

Explanation:

The absolute refractory period of the cardiac muscle action potential refers to the time interval when the voltage gated sodium channels are inactivated. The absolute refractory period lasts ~180 msec. The action potential lasts 200-220 msec.

The refractory period of cardiac muscle is dramatically longer than that of skeletal muscle. This prevents tetanus from occurring and ensures that each contraction is followed by enough time to allow the heart chamber to refill with blood before the next contraction.

In order words, It is important for the cardiac muscle cells to have a longer refractory period, because if they were short like the skeletal muscles, the heart could enter tetanic contraction/summation which is when muscle is stimulated so rapidly that it does not have a chance to relax at all between stimuli.