Q. Arrange the following steps of muscle contraction in the sequence of events occurring first I. Receptor sites on sarcolemma II. Nerve impulse III. Release of $Ca^{2 +}$ IV. Acetylcholine release V. Shortening of sarcomere VI. Synaptic cleft VII. Spread of impulse over sarcolemma on T-tubule The correct option is
A) II $\rightarrow$ IV $\rightarrow$ VI $\rightarrow$ I $\rightarrow$ VII $\rightarrow$ III $\rightarrow$ V
B) II $\rightarrow$ IV $\rightarrow$ I $\rightarrow$ VI $\rightarrow$ VII $\rightarrow$ III $\rightarrow$ V
C) II $\rightarrow$ IV $\rightarrow$ I $\rightarrow$ VI $\rightarrow$ VII $\rightarrow$ V $\rightarrow$ III
D) IV $\rightarrow$ II $\rightarrow$ I $\rightarrow$ VI $\rightarrow$ VII $\rightarrow$ V $\rightarrow$ III
Explanation
Nerve impulse causes $\downarrow$ Acetylcholine release reaches to $\downarrow$ Synaptic cleft $\downarrow$ Sarcolemma have receptor which senses the acetylcholine $\downarrow$ Spread of the impulse through out the T-tubules $\downarrow$ Release of calcium from sarcoplasmic reticulum $\downarrow$ Breakdown of troponin $\downarrow$ Thin and thick filaments slides on each other and contraction starts
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.