HUMAN ANATOMY AND PHYSIOLOGY

 ACTION OF ACETYLCHOLINE AND CONTRACTION OF MUSCLE::

Acetylcholine thus released interacts with nicotinic receptors of the end plate and depolarizes it to generate end plate potential this causes the release of ca++ from the transverse tubules and sarcoplasmic reticulum the ca++ binds to troponin tropomysin and the actin is released the actin thus released interacts with myosin in the presence of ATP and the actin myosin filaments slide over each other to produce contraction 

Relaxation of muscle::

Acetylcholine is rapidly metabolized by the cholinesterase and concentration of calcium goes down as a result of decreased calcium level inhibitory influence is removed from troponin and tropomysin these proteins bind to actin simultaneously myosin ATPase is depressed and subsequently the cross linkage is broken myosin is pulled back to resting position and eventually the muscle is relaxed 



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