Question

Excitation-contraction coupling links two physiological processes. what are these two processes and what constitutes the critical link between these two processes

Answer 1

The link where the action potential of the nerve that meets muscle and causes it to contraction is where excitation-contraction coupling occurs. The  T_tubules the invaginate into the sarcolemma of the muscle cells are the ones that carry the excitation into the muscles. Its depolarization causes the lateral sacs of the sarcoplasmic reticulum to release ca2+ ions. The ca2+ then bind into their site on troponin and causes the tropomyosin to shift and allow actin to expose the binding site in which myosin head will bind and form a cross bridge that is important in the contraction of the muscle.