A Basic Introduction To Sleep

Until the middle of the last century most people thought of sleep as a passive, dormant part of our lives.

We now know, however, that your brain remains very active during sleep. We also know that sleep affects your daily functioning and your physical and mental health in many ways that we are just beginning to understand.

Chemicals produced naturally in the body control whether you are asleep or awake by acting on different parts of the brain.

Neurons in the brainstem, which connects the brain with the spinal cord, produce neurotransmitters, such as serotonin, that keep some parts of the brain active while you are awake. Other neurons at the base of the brain begin signaling when you fall asleep.

These neurons appear to "switch off" the signals that keep you awake. Research also suggests that a chemical called adenosine builds up in your blood while you are awake and causes drowsiness. This chemical gradually breaks down while you sleep.

During sleep, you normally pass through five stages which progress in a repeating cycle.