One of it’s main routes of action is by directly inhibiting regions which are tasked with keeping the brain awake, in particular specialized cells in the hypothalamus which contain the chemical orexin/hypocretin, as well as cholinergic cells (containing the neurotransmitter acetylcholine) in the brain stem. This means that the level of adenosine in particular regions of your brain is an indication of the amount of time you have spent awake that day.Īdenosine promotes sleep by influencing various sleep-wake pathways in the brain. Although it does not so much act as chemical marker for the end of the day, it is critically involved in coordinating the actual process of falling asleep via its action within preoptic cells which inhibit the activity of wake-promoting brain regions.Īdenosine is a byproduct of metabolic and electrical activity within your neurons.
GABA is the main inhibitory neurotransmitter involved in switching off state of wakefulness. These include chemicals such as adenosine, nitric oxide, prostaglandin D2, and a variety of cytokines (cells made by your immune system). Many different sleep promoting factors have been identified. They also contribute to the activation of sleep promoting regions to set in motion the night-time regime of sleeping. This build up generates a sleep propensity - a need for sleep - which, when it reaches a threshold level, helps block the activity in other regions of your brain which are making sure that you stay awake. Over the waking day, the level of these chemicals - or sleep promoting factors as they are called - increases.
When you are awake, the electrochemical activity which generates your thoughts, feelings and decisions generates a series of chemical byproducts. Sleep happens when your sleep promoting regions are active - when they are “winning”.
Sleep and waking result from a dynamic interplay - a tug of war - between regions which are involved in keeping your brain awake, and regions which are involved in keeping your brain in a state of sleep.