Questions and Answers
What happens in Step 1 of excitation-contraction coupling?
Action potential spreads along the sarcolemma to the T-tubules.
What occurs in Step 2 of excitation-contraction coupling?
Calcium is released into the sarcoplasmic reticulum (S.R.).
What is the significance of Step 3 in excitation-contraction coupling?
Calcium binds to actin, removing the blocking action of tropomyosin.
What occurs during Step 4 of excitation-contraction coupling?
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What happens in Step 5 of excitation-contraction coupling?
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What occurs in Step 6 of excitation-contraction coupling?
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Study Notes
Steps in Excitation-Contraction Coupling
- 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.
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Description
This quiz focuses on the steps involved in excitation-contraction coupling, crucial for muscle physiology. It covers the processes initiated by action potentials, the role of calcium ions, and the interactions between actin and myosin during muscle contraction and relaxation.
