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

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

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

The pineal gland is associated with:

The $24$ hour (diurnal) rhythm of our body,such as the sleep-wake cycle,is regulated by the hormone: