Question
Choose the correct statements regarding muscle contraction.
A. A motor neuron carries a signal sent by the Central Nervous System (CNS) to the sarcolemma of the muscle fibre.
B. The neural signal generates an action potential which causes the release of ${Ca}^{+ +}$into sarcoplasm.
C. Increase in ${Ca}^{+ +}$inactivates the actin for breaking cross bridges.
D. Actin binds to the myosin head to form a cross bridge.
E. Shortening of sarcomere takes place, by pulling actin filaments towards the centre of 'A' band.
Choose the correct answer from the options given below:
Options
Solution
Sol. [Key Concept: Muscle contraction — sliding-filament mechanism]
Statements A, B, D and E are correct while statement C is incorrect.
A neural signal reaching neuromuscular junction releases a neurotransmitter (Acetylcholine) which generates an action potential in the sarcolemma. This spreads through muscle fibre and causes the release of ${Ca}^{+ +}$into the sarcoplasm. This ${Ca}^{+ +}$binds to the subunit of troponin on actin filaments and thereby remove the masking of active site for myosin on actin and hence facilitates the formation of cross bridge.
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