Nerve sends impulse to the muscle
The nerve impulse travels down the t-tubules to the muscle cells
Calcium is released from the sarcoplasmic reticulum and binds to troponin
This binding causes tropomyosin to move, exposing myosin binding sites on the actin
Myosin heads using ATP bind to actin and pull the actin inward, shortening the distance between z-lines - this happens in thousands of muscles cells resulting in contraction of the muscle
Adrenal glands
Testis
Ovaries
Pancreas
Thymus
Thyroid