Skeletal Muscle Excitation-Contraction Coupling Mechanism
- vio
- Mar 28, 2023
- 1 min read
1. Acetylcholine released by axon of motor neuron crosses cleft and binds to receptors/channels on motor end plate
2. Action potential generated in response to binding of acetylcholine and subsequent end plate potential is propagated across surface membrane and down T tubules of muscle cell
3. Action potential in T tubule triggers Ca2+ (calcium) release from sarcoplasmic reticulum
4. Calcium ions released from lateral sacs bind to troponin on actin filaments; leads to tropomyosin being physically moved aside to uncover cross-bridge binding sites on actin
5. Myosin cross bridges attach to actin and bend, pulling actin filaments toward center of sarcomere; powered by energy provided by ATP
6. Ca2+ actively taken up by sarcoplasmic reticulum when there is no longer local action potential
7. With Ca2+ no longer bound to troponin, tropomyosin slips back to its blocking position over binding sites on actin; contraction ends; actin slides back to original resting position
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