The structure surrounding the pineal gland in the forebrain is located at:

The amino acid tryptophan is the precursor for the synthesis of

Which of the following helps in the maintenance of the normal rhythm of the sleep-wake cycle?

Which hormone relates with temperature and sleep-wake cycle?

Identify the correct gland on the basis of the following characteristics:
$(I)$ It is located on the dorsal side of the forebrain.
$(II)$ It plays a very important role in the regulation of the $24$-hour rhythm of our body.
$(III)$ It helps in maintaining body temperature.
$(IV)$ Its hormone influences metabolism as well as defense capability.

The pineal gland is associated with: