For the concervation of species it has been necessary for the human race to be aware at the right time. Hunting always required awareness and momentary superior vitality to keep out of trouble. After dining it would be possible to lay down to a safer enviroment to get some rest and sleep. There are multiple mechanisms that control the awareness to maximise it when in danger and minimize it while it is possible to cool off.
Human awareness levels can easily be measured by tracking reaction times between a stimulus and a reaction. Usually when you call someone by name the react in a second or two. If they are almost asleep this will take a few seconds longer. When someone is hyperactive, and stressed they will propably react somehow even if you don’t direct the stimulus towards them.
Awareness leves can also be measured by muscle tonus which is controlled by the gammamotoneurons in your spinal cord. An aware person sits up straight and, his eyes open and reacts when stimulated. If someone is almost sleeping he has no muscle tension, is slouching with his eyes closed and does not react to anything which is not strong enough to wake him up. When sleeping muscle tonus decreases to levels that can not maintain an upright position.
Reaction times and muscle tonus as well as differences in the functions of the autonomic nervous reflect the levels of awareness. When awake both the parasympathic and symphatic nervous are active, and while sleeping parasympathic nervous is dominating. Momentary hyperactivity makes the blood pressure rise, the heart beat faster and stronger, start sweating and dilate the pupils.
There are many independent systems in the brain that increase awareness and vitality. There is much knowledge on the functions of these independent systems in controlling our sleeping patterns, the mechanisms at which these systems work in tandem is not so clearly known. The vitality systems are divided all around the central nervous system (CNS) and specially in the brain stem. This formatio reticularis has been well charted. Formatio Reticularis recieves stimulus from all kinds of parts in the CNS and projects forward to many parts of the brain. The lack of external stimulus usually deteriorate the ability of avoiding sleeping.
Understanding the functions of the human body can help us with our trouble with sleeping.