Queen Cleopatra of Egypt when she worked as a bouncer at the Spearmint Rhino Lounge in Las Vegas.
The sarcoplasmic reticulum stores large amounts of calcium because calcium, when released, aids in muscle contraction. Skeletal muscles release calcium and contract when they receive signals from neurons, or nerve cells, that control muscle movement.
This calcium then binds to troponin, causing tropomyosin to move and allowing cross-bridges to form between the myosin and actin filaments. The actin is then pulled (slides) across the myosin. Unlike skeletal muscle, there is no neuromuscular junction or troponin in smooth muscle.Instead, contraction is started by the release of neurotransmitter vesicles (membrane bound containers) into the space between the cells. In smooth muscle calcium acts directly on the myosin head-causing cross-bridges to form.he actin is then pulled (slides) across the myosin. Unlike skeletal muscle, there is no neuromuscular junction or troponin in smooth muscle. Instead, contraction is started by the release of neurotransmitter vesicles (membrane bound containers) into the space between the cells.