Which of the following is longer?
(a) The refractory period of a cardiac contractile cell.
(b) The refractory period of skeletal muscle fiber.

Verified step by step guidance

1. Step 1: Understand what the refractory period means in muscle physiology. The refractory period is the time during which a muscle cell cannot be re-excited after an action potential has occurred.
2. Step 2: Recall that cardiac contractile cells have a unique action potential characterized by a plateau phase, which prolongs their refractory period to prevent tetanus and allow proper heart filling.
3. Step 3: Compare this to skeletal muscle fibers, which have a much shorter refractory period because their action potentials are brief, allowing rapid repeated contractions.
4. Step 4: Recognize that the longer refractory period in cardiac muscle ensures rhythmic contractions and prevents summation, while the shorter refractory period in skeletal muscle allows for quick, repeated contractions.
5. Step 5: Conclude that the refractory period of a cardiac contractile cell is longer than that of a skeletal muscle fiber due to the physiological differences in their action potentials and functional requirements.

Key Concepts

Refractory Period

The refractory period is the time during which a muscle cell cannot be re-excited after an action potential. It ensures proper timing of contractions and prevents continuous, uncontrolled stimulation. Understanding this period is essential to compare different muscle types.

Cardiac Contractile Cell Physiology

Cardiac contractile cells have a prolonged action potential due to calcium influx, resulting in a longer refractory period. This extended refractory period prevents tetanus and allows the heart to relax between beats, ensuring effective pumping.

Skeletal Muscle Fiber Physiology

Skeletal muscle fibers have a shorter refractory period because their action potentials are brief, allowing rapid repeated contractions. This enables skeletal muscles to sustain tetanic contractions necessary for voluntary movements.