Daily rhythms are usually associated with

The diurnal rhythms are regulated by . . . . . . .

$P$ is a small,round,reddish structure located on the dorsal side of the forebrain. It contains a stalk and releases a hormone $Q$ which controls the diurnal rhythm of the body. $P$ and $Q$ are

Suggest a suitable word for the fourth place: Darkening of skin : $MSH$ :: Lightening of skin : .......

Melatonin is secreted by the . . . . . . .

The amino acid tryptophan is the precursor for the synthesis of