Final answer:
Cardiac muscle cannot exhibit tetany due to its long refractory period, which ensures effective blood pumping by allowing complete relaxation between contractions. This is essential for survival as tetany would prevent the heart from functioning properly. Option d.
Step-by-step explanation:
As a result of the long refractory period in the contractile cell of cardiac muscle, it cannot exhibit tetany. Cardiac muscle cells undergo twitch-type contractions where the long refractory period, comprising both an absolute refractory period of approximately 200 ms and a relative refractory period of approximately 50 ms, prevents any possibility of tetany. This is crucial for life, as it ensures that the heart muscle contracts and relaxes in a way that enables effective blood pumping.
The long refractory period seen in cardiac contractile cells is reflected in their action potentials, which feature a characteristic plateau phase due to the influx of calcium ions. This plateau phase ensures that each contraction is complete before another electrical impulse can trigger a subsequent contraction, preventing tetany—a sustained involuntary muscle contraction that would be fatal if it occurred in the heart.
Thus, due to this extended refractory period, cardiac muscle cannot exhibit tetany (D), but must still undergo aerobic respiration to fulfill its energy demands, primarily metabolizing lipids and carbohydrates, and is resistant to fatigue due to its capacity for aerobic metabolism and stores of myoglobin, lipids, and glycogen.