Question

What are the three phases of a muscle twitch?

Answer 1

A muscle twitch consists of a latent period, a contraction phase, and a relaxation phase.

Step-by-step explanation:

A muscle twitch consists of three phases: a latent period, a contraction phase, and a relaxation phase.

1. The latent period is the time between the stimulus and the beginning of muscle contraction. During this phase, the action potential is being propagated along the sarcolemma, and Ca+ ions are released from the sarcoplasmic reticulum (SR).
2. The contraction phase is when the tension in the muscle increases. During this phase, Ca+ ions bind to troponin, tropomyosin moves away from actin binding sites, cross-bridges form, and sarcomeres shorten.
3. The relaxation phase is when the tension in the muscle decreases. Ca+ ions are pumped out of the sarcoplasm, and cross-bridge cycling stops. This returns the muscle to its resting state.

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