Assertion: on stimulation, a muscle cell releases calcium ions `(Ca^(2+))` from sarcoplasmic reticulum.
Reason: By reacting with a protien complex, `Ca^(2+)` uncover active sites on the actin filaments.

Options

A. If both assertion and reason are ture and reason is the corect explanation of assertion
B. If both assertion and reason are ture but reson is not the correct explanation of assertion
C. If assertion is true reason is false
D. If both assertion and reason are false

Answer

b

Explanation

A neural signal on reaching the nerromuscular junction releases a neutrosmitter (acetylcholine) which generates an action potential in the sarcolemma. This spreads through the muscle fibre and causes the release of calcuim ions from sarcoplasmic reticulum into the sarcoplasm. Increase in `Ca^(2+)` level leads to the binding of calcium with a subunit of troponin on actin filaments and thereby removing the mask of active sites for myosin.