Choose the correct statements regarding muscle contraction. Choose the correct answer from the options given below:
- A and B only
- C and E only
- C and D only
- A, B, D and E only
Answer
(4) A, B, D and E only
Solution
As per NCERT,
A – correct: a signal from the CNS reaches the sarcolemma through a motor neuron (neuromuscular junction).
B – correct: the action potential releases Ca++ into the sarcoplasm.
C – incorrect: increased Ca++ binds troponin and removes the masking of active sites on actin, so actin is activated and cross bridges form.
D – correct: the myosin head binds to the exposed active sites on actin to form a cross bridge.
E – correct: the cross bridges pull the actin filaments towards the centre of the 'A' band, shortening the sarcomere.
∴ Correct statements: A, B, D and E
Answer: (4)