The Mechanism of daily wake and sleep

The Mechanism of  daily wake and sleep

Circadian rhythms are biological changes that occur at roughly 24-hour intervals, whether we’re aware of the time on our watch or not. These changes,which are controlled by internal biological time-keeping systems, affect us physically,mentally and behaviorally.

Located behind the eyes in the hypothalamus is a region of the brain called the suprachiasmatic nucleus(SCN in short). No larger than a grain of rice, the SCN is a kind of master body clock that controls all our other internal clocks, which in turn control our circadian rhythms,or daily wake-sleep cycles.Circadian rhythms respond mainly to light and dark cues but even if the body was monitored under conditions devoid of day or night signals, our circadian rhythms still cycle in a period of around 24 hours. The retina in the eye senses light level information, which is relayed to the SCN, which sends a signal to the pineal gland. This pea-sized gland, located beneath the thalamus, is responsible for the secretion of melatonin—a hormone that tells the body to sleep - and so at night when light levels fall, the production of melatonin Increases,telling us to head to bed.

Are you a lark or an owl?
We all know that our genes make us different, and this also affects our individual natural rhythms.Some people have a body clock that lasts langer than 24 hours, which means they tend to stay up later:these people are referred to as owls. Other people with shorter body clocks, meanwhile, tend to rise earlier in the ,morning people like this are larks.

What trggers the sleep-wake cycle?
The variations in the amount of melatonin secreted by the body create a daily rhythm of rising and falling hormone levels. These hormones, along with the SNC, affect apoetite, body temperature and a lot else.