Zoology - Locomotion and Movement Question with Solution | TestHub
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 into sarcoplasm.
C. Increase in 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 thecorrectanswer from the options given below :NEET 2026 (Cancelled)
Options:
Answer:
Solution:
Statement A is correct: Muscle contraction is initiated by a signal sent by the Central Nervous System (CNS) via a motor neuron to the neuromuscular junction, which is the junction between a motor neuron and the sarcolemma of the muscle fibre.
Statement B is correct: The neural signal releases a neurotransmitter (acetylcholine) which generates an action potential in the sarcolemma. This action potential spreads through the muscle fibre and causes the release of ions into the sarcoplasm.
Statement C is incorrect: An increase in level leads to the binding of calcium with a subunit of troponin on actin filaments, which removes the masking of active sites for myosin. It does not inactivate actin.
Statement D is correct: Utilising the energy from ATP hydrolysis, the myosin head binds to the exposed active sites on actin to form a cross bridge.
Statement E is correct: The formation of cross bridges pulls the attached actin filaments towards the centre of the 'A' band. The 'Z' lines attached to these actins are also pulled inwards, causing a shortening of the sarcomere, which is muscle contraction.
Therefore, statements A, B, D, and E are correct.
Answer: A, B, D and E only
