Which hormone is secreted more in dark conditions?

"Pinealocytes" are found in which of the following?

The pineal body originates from:

Artificial light, extended work-time and reduced sleep-time disrupt the activity of

$I.$ Sleep-wake cycle, $II.$ Body temperature, $III.$ Pigmentation, $IV.$ Metabolism, $V.$ Defense capability. All of the above-written activities are influenced/regulated by:

"Brain sand" is found in .....