Question

Please explain the process of Excitation-Contraction Coupling. Make sure to discuss all channels and structures involved, including ATP, any ions, actin, myosin any regulatory proteins, organelles, motor neuron, sarcolemma, ect. In other words, explain it using all of the details I discussed in class.

Answer 1

The excitation contraction coupling is a sequence of events that occurs during contraction of skeletal muscles. The term was first coined by Alexander Sandow in the year 1952. Excitation contraction coupling describes the electrical events that takes place in the plasma membrane of skeletal muscles. The entire process is described in detail in the following steps,

1. Nerve impulse arrives at the axon terminal andvtriggers the release of acetyl choline from synaptic vesicles
2. Acetyl choline diffuses across the synaptic cleft and binds to its receptor on the motor end plate where it triggers muscle action potential
3. The excess acetyl choline in the synaptic cleft is cleaved by the enzyme acetyl choline esterase
4. The muscle action potential travels along the T tubules and triggers calcium ion release from sarcoplasmic reticulum
5. The calcium ions binds with troponin on the thin filament. This exposes the binding site on myosin
6. Myosin heads bind to actin. Thin filaments are pulled towards the center of the sarcomere. This is called as power stroke and requires energy in the form of ATP
7. As the levels of calcium decreases, calcium is actively transported out of the sarcoplasmic reticulum
8. The troponin-tropomyosin complex slides back into position
9. The myosin binding sites on actin is blocked
10. The muscle relaxes