Muscle contraction and nervous system

muscle fibre consists of thin and thick filament.Thin filament is made up of actin filament with troponin attached to it.The thick filament consists of the myosin filament .Myosin filament has a head and a tail.The myosin head contain ATPase enzyme.

For a muscular contraction to be carried out,the nervous system transmits nerve impulse to the neuromuscular junction.This causes the presynaptic membrane to release acetycholine to the synaptic cleft.This neurotransmitters enter the postsynaptic membrane and causes depolarisation of post synaptic membrane.Action potential is generated and nerve impulse is transmited to the sarcolemma and to the sarcoplasmic reticulum.This cause sarcoplasmic reticulum to release calcium ions to the sarcoplasm.The calcium ion binds to the troponin and causes the binding site of the actin filament to be exposed.calcium ion also binds to the myosin head and causes the ATP on the head to undergo hydrolysis to form ADP and P which are still attached to the myosin head.The myosin head is energised and it bind to the binding site of the actin filament to form actomyosin cross-bridge.The myosin head pulls the actin filament slide over the thick filament .Another ATP attaches to the myosin head and causes comformational change of the myosin head.The head detaches from the actin filament and is hydrolysed again.The attaching and detaching processes cause muscle to contract.After muscle contraction, the calcium ions detach from the myosin head and troponin.They are collected back into the sarcoplasmic reticulum.Acetylcholinesterase hydrolyses the acetylcholine.The neuromuscular junction returns to its resting state.the muscle is relaxed.