PHYSIOLOGY
SYNAPTIC PHYSIOLOGY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Acetylcholinesterase enzymes must break down acetylcholine in synaptic cleft
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Myosin heads release actin filament
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Calcium must be pumped back into sarcoplasmic reticulum
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Tropomyosin changes shape to cover binding sites
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Detailed explanation-1: -Muscle contraction usually stops when signaling from the motor neuron ends, which repolarizes the sarcolemma and T-tubules, and closes the calcium channels in the SR. Ca++ ions are then pumped back into the SR, which causes the tropomyosin to re-cover the binding sites on actin (Figure 10.3. 2).
Detailed explanation-2: -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: -Tropomyosin blocks myosin binding sites on actin molecules, preventing cross-bridge formation, which prevents contraction in a muscle without nervous input.
Detailed explanation-4: -Muscle contraction thus results from an interaction between the actin and myosin filaments that generates their movement relative to one another. The molecular basis for this interaction is the binding of myosin to actin filaments, allowing myosin to function as a motor that drives filament sliding.