Chemical Coordination and Regulation Question 77
77. Which one of the following is not a second messenger in hormone action?
(a) Calcium
(b) Sodium
(c) cAMP
(d) cGMP
Show Answer
Answer : b
Hints & Solutions
(b) In heart cells cAMP acts as secondary messenger which is made in the response of adrenaline and it stimulates $Ca^{2+}$ ions to come out from the sarcoplasmic reticulum of muscle fibres which causes muscle contraction. cGMP (Cyclic Guanosine Monophosphate) which acts as secondary messenger works on the action of acetylcholine, increase in flow of $Ca^{2+}$ into muscle fibres & hence causes muscle relaxation. There is no role of sodium in hormonal action.
