PHYSIOLOGY
MUSCLE CONTRACTION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Release of calcium from sarcoplasmic reticulum
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Tropomyosin covers myosin binding site
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Acetyl choline released into synapse
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No cross bride formation
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ATP binds to myosin head
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Detailed explanation-1: -ATP binding causes myosin to release actin, allowing actin and myosin to detach from each other. After this happens, the newly bound ATP is converted to ADP and inorganic phosphate, Pi.
Detailed explanation-2: -4. 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-3: -Step 2: ATP binding to the myosin head domain induces a small conformational shift in the actin-binding site that reduces its affinity for actin and causes the myosin head to release the actin filament.
Detailed explanation-4: -ATP then binds to myosin, moving the myosin to its high-energy state, releasing the myosin head from the actin active site. ATP can then attach to myosin, which allows the cross-bridge cycle to start again; further muscle contraction can occur.
Detailed explanation-5: -ATP is used during relaxation to break the bond between the myosin heads and the actin filament. Additionally, ATP is needed to actively pump calcium ions back into the sarcoplasmic reticulum.