Muscle Physiology: Excitation-Contraction Coupling

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Action potential spreads along the sarcolemma to the T-tubules.

Calcium is released into the sarcoplasmic reticulum (S.R.).

Calcium binds to actin, removing the blocking action of tropomyosin.

Myosin heads attach to begin contraction. Signup and view all the answers

Calcium is removed and the binding sites on actin become blocked again by tropomyosin. Signup and view all the answers

Muscle relaxes. Signup and view all the answers

Action potential spreads along the sarcolemma to the T-tubules.

Calcium is released into the sarcoplasmic reticulum (S.R.).

Calcium binds to actin, removing the blocking action of tropomyosin.

Myosin heads attach to begin contraction.

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Calcium is removed and the binding sites on actin become blocked again by tropomyosin.

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Muscle relaxes.

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Action potentials travel along the sarcolemma and into the transverse tubules (T-tubules), initiating the contraction process.
The arrival of the action potential triggers the release of calcium ions from the sarcoplasmic reticulum (S.R.), crucial for muscle contraction.
Calcium ions bind to actin, leading to the removal of tropomyosin, which previously blocked the binding sites necessary for contraction.
Myosin heads attach to the now-exposed binding sites on actin, facilitating the contraction of the muscle fibers.
Following contraction, calcium ions are transported back into the sarcoplasmic reticulum, causing the tropomyosin to re-block the binding sites on actin.
Muscle relaxation occurs as a result of the blocking of actin by tropomyosin, halting the contraction cycle.