Sleep

Sleep is a nature activity of humans is also behavioral sense some body called god’s gift but here we know some scientific terms of sleep.

Sleep is a behavioral adaptation of vertebrate animals with much to teach the cognitive scientist about the relationship of mind to brain. In no other behavioral state are the differences from waking psychology so profound or so clearly tied to the underlying changes in neurophysiology. It is this psycho physiological concomitance that will be emphasized in the account given here of the natural history and neurobiology of sleep.

As a behavior, sleep is characterized by
(1) a recumbent posture with varying degrees of relaxation of the skeletal musculature;
(2) an increase in the threshold of response to sensory stimuli; and
(3) a characteristic set of electrographic signs.

From an evolutionary point of view sleep is clearly a strategy for energy conservation and for protection from predators since all animals sleep attimes and in places that confer a benefit in one or both of these domains. Sleep is distinguished from simple rest, from torpor, and from anesthetics or traumatic unresponsiveness by its active and distinctive brain mechanisms of induction and maintenance, as well as by its ready reversibility.

Here u sees the type of sleep of humans and sensitive wave of every sleep:

The following diagram is REM cells of sleeping systems

Reciprocal Interaction. (A) Structural model. REM-on cells of the pontine reticular formation are cholino ceptively excited and/or cholinergic ally excitatory (ACH+) at their synaptic endings (open boxes). Pontine REM-off cells are noradrenergic ally (NE) or serotonergically (5HT) inhibitory (–) at their synapses (filled boxes). (B) Dynamic model. During waking the pontine aminergic (filled box) system is tonic ally activated and inhibits the pontine cholinergic (open box) system. During NREM sleep aminergic inhibition gradually wanes and cholinergic excitation reciprocally waxes. At REM sleep onset aminergic inhibition is shut off and cholinergic excitation reaches its high point. (C) Activation level (A). As a consequence of the interplay of the neuronal systems shown in A and B, the net activation level of the brain (A) is at equally high levels in waking and REM sleep and at about half this peak level in NREM sleep.