Question

If we repeatedly stimulate a myocardial cell, and a skeletal muscle cells every 50 ms, what are the differences of muscle tension between these two types of cells? Explain why contractions in cardiac muscle cells are different to skeletal muscle cells

Answer 1

In skeletal muscles, action potential is generated by a nerve impulse. The duration of this action potential is 2-4ms. The duration of refractory period is 1-3ms.

On the other hand, in myocardial cell, action potential is generated by the pacemaker. The duration of action potential is 300ms, and the duration of refractory period is 200ms.

So, after 50ms, a skeletal muscle will be ready to generate a second action potential, while a myocardial cell will not be able to generate a second action potential. In cardiac muscles, the muscle is already contracted (in a state of tension), so it will not contract again; while in skeletal muscle the muscle will be relaxed after 50ms.

Contractions are different in both types of cells, because of striations in muscle cells which are not present in cardiac muscles.