EXSS155 Muscle Contractions Cycle

First

Nerve impulse arrives at axon terminal which opens voltage-gated calcium channels.

Second

The presence of calcium causes the synaptic vesicles to release their contents (often acetycholine, ACh) into the synaptic cleft.

Third

ACh binds to receptors on the miscle motor end plate; this opens Na^+ channels and Na⁺ rushes into the cell.

Fourth

Inside of the muscle cell becomes more positive, triggers muscle action potential that spreads over sarcolemma and down the transverse tubules.

Fifth

The release of Ca²⁺ from the SR is triggered and the muscle cell will shorten and generat force.

Sixth

Ca²⁺ binds to troponin and causes troponintropomyosin complex to move and reveal myosin bonding sites on actin.

Seventh

The contraction cycle begins