PHYSIOLOGY
SYNAPTIC PHYSIOLOGY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Ca++ is removed from the actin and it goes back to its original shape
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Myosin and actin are cross bridge connected
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Z-lines are brought closer together
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AChE is inactive
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Detailed explanation-1: -Muscle contraction ends when calcium ions are pumped back into the sarcoplasmic reticulum, allowing the muscle cell to relax. During stimulation of the muscle cell, the motor neuron releases the neurotransmitter acetylcholine, which then binds to a post-synaptic nicotinic acetylcholine receptor.
Detailed explanation-2: -In addition, muscle relaxation is possible when Ca2+ is reabsorbed by the sarcoplasmic reticulum and during this process Ca2+-ATPase (the Ca2+ pump) plays a key role. This process of Ca2+ uptake by the sarcoplasmic reticulum via Ca2+-ATPase reduces intramuscular Ca2+ concentrations and results in muscle relaxation.
Detailed explanation-3: -Relaxation: Relaxation occurs when stimulation of the nerve stops. Calcium is then pumped back into the sarcoplasmic reticulum breaking the link between actin and myosin. Actin and myosin return to their unbound state causing the muscle to relax.
Detailed explanation-4: -Stimulation of the muscle fibre, causes a wave of depolarisation to pass down the t-tubule, and the SR to release calcium ions into the sarcoplasm. Calcium is pumped back up into the SR to lower calcium ion concentration in the sarcoplasm, to relax the muscle (turn off contraction).