A muscle cramp is a sudden, painful contraction of a muscle during which movement is difficult. What is happening at the cellular level during a musde cramp?
A. A lack of calcium causes the sarcomeres to lock together. preventing relaxation.
B. Myosin and actin do not fully detach, so the muscle cannot relax.
C. The motor neuron does not send a signal, so the muscle cannot relax.
D. The proteins in the myofibrils become denatured, preventing relaxation.