(b) In heart cells AMP acts as secondary messenger which is made in the response of adrenaline and it stimulates Ca2+ 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 Ca2+ into muscle fibres & hence causes muscle relaxation. There is no role of sodium in hormonal action
Which one of the following is not a second messenger in hormone action ? (a) Calcium (b) Sodium (c) cAMP (d) cGMP
