Question

1. Sleep is very important to everyone, discuss mechanisms that regulate sleep.

Answer 1

Ans) Sleep is regulated by two parallel mechanisms, homeostatic regulation and circadian regulation, controlled by the hypothalamus and the suprachiasmatic nucleus (SCN), respectively.

- The ventrolateral preoptic nucleus (VLPO or VLPN) of the hypothalamus is one area of the brain that is particularly involved in the switch between wakefulness and sleep. Neurons in this small area help to promote sleep by inhibiting activity in areas of the brain stem that maintain wakefulness.

- Although the exact nature of sleep drive is unknown, homeostatic pressure builds up during wakefulness and this continues until the person goes to sleep.

- Adenosine is thought to play a critical role in this and many people have proposed that the pressure build-up is partially due to adenosine accumulation.

- However, some researchers have shown that accumulation alone does not explain this phenomenon completely.

- The circadian rhythm is a 24-hour cycle in the body, which has been shown to continue even in the absence of environmental cues. This is caused by projections from the SCN to the brain stem.