Question

the following events are associated with muscle contraction. which one of the following lists the correct order in which these events occur following the initiation of a contraction by a nerve impulse?

1. t-tubules transmit electrical impulses throughout the muscle cell.
2. myosin contacts actin and pulls it toward the center of the sarcomere.
3. acetylcholine binds to receptors on the muscle.
4. troponin-tropomyosin complex shifts to expose myosin binding sites.
5. calcium is released from the sarcoplasmic reticulum.

3, 1, 5, 4, 2
3, 5, 1, 4, 2
4, 2, 1, 3, 5
1, 3, 5, 2, 4
3, 5, 1, 2, 4

Explanation:

1. First, the nerve impulse triggers the release of acetylcholine, which binds to muscle receptors (step 3).
2. This binding initiates an electrical signal that travels through T-tubules in the muscle cell (step 1).
3. The T-tubule signal stimulates calcium release from the sarcoplasmic reticulum (step 5).
4. Calcium binds to troponin, causing the troponin-tropomyosin complex to shift and expose myosin binding sites on actin (step 4).
5. Finally, myosin contacts actin and pulls it to shorten the sarcomere (step 2).

Answer:

3, 1, 5, 4, 2