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Following is given in a randomly arranged list of events that occur at neuromuscular junction to trigger muscle contraction 

1) Receptor sites on sarcolemma 

2) Nerve impulse 

3) Release of Ca2+ from sarcoplasmic is reticulum

4) The neurotransmitter acetylcholine is released 

5) Sarcomere shorten 

6) Synaptic cleft 

7) Spread of impulses over sarcolemma on T- tubules 

Which of the following gives the correct sequence of these steps ? 

Option: 1

2 --> 4 --> 1 --> 6 --> 7 -->  3 -->  5 


Option: 2

2--> 4 --> 6 --> 1 --> 7 --> 3 --> 5  


Option: 3

1 --> 2 --> 3  -->  4 --> 5 --> 6 --> 7 


Option: 4

7 --> 6 --> 5 --> 4 --> 3 --> 2 --> 1 


Answers (1)

best_answer
  • Nerve impulse (2) is generated and travels down the motor neuron.
  • The neurotransmitter acetylcholine (4) is released into the synaptic cleft (6).
  • Acetylcholine binds to the receptor sites on the sarcolemma (1).
  • This binding initiates an impulse that spreads over the sarcolemma and into the T-tubules (7).
  • The impulse triggers the release of Ca2+ from the sarcoplasmic reticulum (3).
  • The released Ca2+ binds to the troponin molecules in the muscle fiber, which allows the myosin and actin filaments to interact.
  • The interaction of myosin and actin filaments results in the shortening of the sarcomeres (5), leading to muscle contraction.

Therefore, Option 2) is the correct sequence.

 

 

Posted by

Rakesh

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