Neural Stimulation:

Initiated by nerve impulse, releasing acetylcholine at neuromuscular junction.

Acetylcholine binds to sarcolemma receptors on the muscle cell membrane.

Action Potential Propagation:

Action potential travels along sarcolemma and into transverse tubules (T-tubules).

Calcium Release:

Action potential triggers release of calcium ions from sarcoplasmic reticulum (SR).

Troponin and Tropomyosin Interaction:

Calcium binds to troponin, causing conformational changes.

Tropomyosin shifts, exposing myosin-binding sites on actin.

Cross-Bridge Formation:

Myosin heads bind to exposed actin sites, forming cross-bridges.

Contraction:

ATP hydrolysis and power strokes lead to sliding of actin and myosin filaments, inducing muscle contraction.

Relaxation:

Calcium actively transported back into SR

Review: Enzymes I and II (The Living Cell)