Question

Give a brief detail of the physiologic steps to muscle contraction. Explain with support of the appropriate chapters in your book.

Answer 1

Muscle contraction starts from the arrival of nerve impulse to neuromuscular junction. The nerve impulse reaching the peesyy membrane leads to the opening of voltage gated calcium channels and leads to the fusion of ACH vescicles to the membrane. Acetylcholine is released to the synaptic cleft. The acetylcholine then binds to the receptor in the motor end plate of post synaptic membrane. This leads to the influx of Na+ and efflux of K+. The calcium is released as part of it by the sarcoplasmic reticulum via T tubules. The calcium ions that reach the sarcolemma then binds with the tropin and remove the troponin tropomyosin blockage that blocks the active sites if actin. Actin is the light filament and myosin is the daek filament. The myosin head that contains the ATP is hydrolysed and leads to ADP production. The myosin head reaches a high energy State and binda to actin firming cross bridge. Thus the contraction starts. The actin and myosin slides over each other forming extensive contraction. During this time the sarcomere length is reducing. The H zone the space between the actin filaments are reducing and the sarcomere length is reducing to its maximum. After that the cross bridge breaks and the ADP is phosphorylated. Now the actin active site is blocked by the troponin tropomyosin blockage. Now the acetylcholine is getting degraded by acetylcholine choline esterase leading to relaxation of muscles. This is how muscle contraction and relaxation occurs.