summation. When a muscle fiber (or motor unit) has sustained its maximum force,
ID: 3506285 • Letter: S
Question
summation. When a muscle fiber (or motor unit) has sustained its maximum force, this is known as tetanus, as all myosin heads are participating in cross-bridge cycles. 2. Put the following events of excitation-contraction coupling in the correct sequential order Ca2+ released from the sarcoplasmic reticulum. Action potentials propagate across the plasma membrane (sarcolemma) and t-tubules of the muscle fiber. Acetylcholine diffuses across the neuromuscular cleft. Ca2 binds to troponin and causes tropomyosin to shift. A wave of action potentials travels down the motor neuron, prompting exocytosis of Acetylcholine into the synaptic cleft. Myosin heads bind to actin filaments and initiate the cross-bridge cycles. To increase the force or tension generated by a single muscle, there are two strategies. One is to increas the frequency of action potentials firing on a motor unit to achieve summation. Thus, a single motor un can increase its tension beyond a single twitch by summating the twitches. A complementary approach is t simply activate more motor units in a muscle. The latter is referred to as motor unit recruitment. A skeletal muscle contraction will generate enough tension to counter the load of the task. When you lift 5 lb. weight during a biceps curl, you are only activating enough motor units to perform the task. If yo switch to a 10 lb. weight, you would need to recruit more motor units in your biceps to accommodate th additional load. To produce a smooth, sustained muscle contraction at sub- contracting back muscles to stand for long periods of time), your CNS will activate different motor units a muscle in a rotating fashion. This prevents fatigue of any one motor unit. This concept (rotation of mot units to continually provide the same sustained contraction) is called asynehronous recruitment. Finall even when a muscle is at rest, a small number of motor units are still recruited to maintain the muscle t This is muscle tonus. maximum force (lil 3. Contrast between the following terms. Asynchronous recruitment- Motor unit recruitment- Summation - Tonus -Explanation / Answer
Answer
2)
Events in excitation-contraction coupling in correct order :
3)
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