Answer:
THERMOSTAT
-Most of us tend to wake up on a morning with the unwelcome sound of an alarm clock telling us it's time to go to work.
But now scientists believe they have discovered the switch which flips in our brains causing us to naturally wake up.Sleep is governed both the circadian clock and the sleep homeostat
External factors such as daylight and temperature control circadian clock
Scientists have discovered how to operate the 'switch' in the brain
But what naturally triggers the 'sleep thermostat' is still a mystery
