If you find going to sleep a breeze then you have probably not put much thought into what influences when we go to sleep and when we wake up. If, on the other hand, you have trouble going to sleep, then you have probably lain in bed for hours pondering that exact question.
Interestingly, there are two specific areas of the brain that regulate sleeping and waking. One is essentially a sleep inducing area and one is a wakefulness inducing area. It is the interplay between these two areas of the brain that wake us, put us to sleep and ensure that we stay in either state for a certain amount of time.
Both areas release different neurotransmitters and it is the levels and relationships between these neurotransmitters that determines when we go to sleep, when we wake up and how long we are awake or asleep. One of the key influences on these neurotransmitters is our body clock. It is believed that as we are awake or asleep these neurotransmitters build up in one or the other area and once they have reached certain levels they will induce us to wake or go to sleep. In some respects, it is like an hourglass, where the sand falls though to the other side and once one side has run out it is time to turn it over with each turn representing being awake or asleep.