Question

Which statements about muscle contractions are true?
(i) Acetylcholine is released when neural signal reaches motor end plate
(ii) Muscle contraction is initiated by a signal sent by CNS via a sensory neuron
(iii) During muscle contraction, isotropic band gets elongated
(iv) Repeated activation of the muscle can lead to lactic acid accumulation.

• A. i and iv
• B. i and iii
• C. ii and iii
• D. i, ii and iii
• E. i and ii

Answer 1

The correct option is A i and iv

• Acetylcholine is the neurotransmitter used at the neuromuscular junction, it is the chemical that motor neurons of the nervous system release in order to activate muscles when acetylcholine is released when the neural signal reaches motor end plate.
• Repeated activation of muscle induces processes resulting in decreased performance (fatigue) as well as enhanced performance (potentiation). Lactic acid is formed and accumulated in the muscle under conditions of high energy demand, rapid fluctuations of the energy requirement and insufficient supply of O2. Hence, Repeated activation of the muscle can lead to lactic acid accumulation.

So, the correct answer is ' i and iv'.