NEETZoologyNeural Control and Coordination
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): All the muscle fibres innervated by a single motor neuron contract simultaneously when a signal is sent by the central nervous system. Reason (R): The motor neuron releases acetylcholine at the neuromuscular junctions of all the muscle fibres it innervates upon receiving an action potential. In the
Options
- ABoth (A) and (R) are correct and (R) is the correct explanation of (A)
- BBoth (A) and (R) are correct but (R) is not the correct explanation of (A)
- C(A) is correct but (R) is not correct
- D(A) is not correct but (R) is correct
Correct answer
A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
Step-by-step solution
A motor neuron along with all the muscle fibres connected to it constitute a motor unit. When an action potential from the central nervous system reaches the axon terminals of the motor neuron, it simultaneously releases the neurotransmitter acetylcholine at all the neuromuscular junctions it forms. This generates an action potential in the sarcolemma of all these connected muscle fibres at the same time, leading to their simultaneous contraction. Therefore, both the Assertion and the Reason are correct, and the Re