Question

The action potential in the sarcolemma travels along the T tubules to the triads, where it triggers the release of Ca₂⁺ from the terminal cisternae of the sarcoplasmic reticulum?

Answer 1

The student's question pertains to the steps involved in muscle fiber contraction, which starts with acetylcholine release and culminates in calcium release from the sarcoplasmic reticulum, triggering muscle contraction.

Step-by-step explanation:

The process described by the student involves an action potential that initiates muscle contraction. Here are the basic steps:

• Acetylcholine (ACh) is released from the axon terminal, binding to receptors on the sarcolemma, which is the muscle fiber's cell membrane.
• This binding generates an action potential that travels along the sarcolemma and down the T-tubules, which are extensions of the cell membrane that penetrate into the cell's interior.
• As the action potential propagates down the T-tubules, it reaches the triads, where it triggers the opening of calcium channels in the membrane of the adjacent sarcoplasmic reticulum (SR).
• Calcium ions (Ca2+) are then released from the SR into the sarcoplasm, initiating contraction of the muscle fiber's sarcomeres, the basic unit of muscle contraction.