Question

Arrange the following events in the correct sequence during muscle relaxation:

The nerve signal ceases
AChE breaks ACh down
Active transport pumps in the sarcoplasmic reticulum begin to pump calcium back into the cisternae
Calcium releases from troponin
Tropomyosin covers the myosin binding sites
Options:
a) 2, 3, 4, 5, 1
b) 1, 3, 2, 5, 4
c) 1, 2, 4, 3, 5
d) 3, 2, 4, 1, 5

Answer 1

The correct sequence of events during muscle relaxation following the cessation of a nerve signal is: 1) The nerve signal ceases, 2) AChE breaks down ACh, 3) Calcium is pumped back into the sarcoplasmic reticulum, 4) Calcium releases from troponin, and 5) Tropomyosin covers the myosin binding sites on actin (sequence c).

Step-by-step explanation:

To arrange the events during muscle relaxation in the correct sequence, you need to understand the steps involved in this process. Once the nerve signal ceases, acetylcholinesterase (AChE) breaks down acetylcholine (ACh), ending the stimulatory signal. The sarcoplasmic reticulum then pumps calcium ions back into its cisternae, using active transport. This decrease in calcium concentration leads to calcium releasing from troponin. Finally, tropomyosin moves to cover the myosin binding sites on actin, thereby preventing muscle contraction. Hence, the sequence is:

1. The nerve signal ceases.
2. AChE breaks ACh down.
3. Active transport pumps in the sarcoplasmic reticulum begin to pump calcium back into the cisternae.
4. Calcium releases from troponin.
5. Tropomyosin covers the myosin binding sites.

Therefore, the correct sequence from the options given is (c) 1, 2, 3, 4, 5.