Question

Read the statements about the mechanism of muscle contraction and select the correct answer.
I. Acetylcholine is released when the neural signal reaches the 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 muscles can lead to lactic acid accumulation.

• A. I and IV alone are correct.
• B. I and III alone are correct.
• C. II and III alone are correct.
• D. I, II and III alone are correct.
• E. I and II alone are correct.

Answer 1

The correct option is A I and IV alone are correct.

• Acetylcholine (ACh) is a neurotransmitter released by motor neurons that binds to receptors in the motor endplate when the neural signal reaches the motor endplate. Neurotransmitter release occurs when an action potential travels down the motor neuron's axon, resulting in altered permeability of the synaptic terminal membrane and an influx of calcium. Hence statement I is correct.
• Repeated activation of the muscles can cause the anaerobic breakdown of glucose which leads to the formation of lactic acid and its accumulation. Accumulation of lactic acid can irritate muscles and cause discomfort and soreness. Hence Statement IV is correct.
  
• So, the correct answer is 'I and IV alone are correct'.