$I. ACTH$,$II. GH$,$III. MSH$,$IV. FSH$,$V. LH$,$VI. Oxytocin$. Which of the above hormones are polypeptide in nature?

Which of the following acts as a second messenger?

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A)$: $FSH$,which interacts with membrane-bound receptors,does not enter the target cell.
Reason $(R)$: Binding of $FSH$ to its receptors generates a second messenger (cyclic $AMP$) for its biochemical and physiological responses.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which of the following hormones is derived from an amino acid?

In heart cells,which molecule acts as a second messenger and increases the contraction of muscle cells in response to adrenaline?

The secondary messenger which shows an antagonistic effect to $cAMP$ in heart muscle is