Neurophysiology Of Sleep:

 REM sleep is characterized by increased parasympathetic activity and variable sympathetic activity related to increased activation of certain brain functions. The states of wakefulness and sleep are characterized as stages that are defined by stereotypical EEG, EMG, and EOG patterns. Wakefulness, orthodox sleep , and paradoxical sleep are three distinct states of existence. Each state has characteristic behavioral and physiologic patterns, and each has specific neurophysiologic mechanisms related to its generation and control. Structures within the brainstem use various neurotransmitters to influence higher brain structures within the midbrain and cortex. The ARAS provides cholinergic, noradrenergic, and glutaminergic stimulation to the thalamus, hypothalamus, and basal forebrain leading to cholinergic and glutaminergic excitation of the cortex. a lively cortex that exhibits a characteristic pattern of desynchronized EEG manifests wakefulness. Various factors affect the necessity and timing of sleep onset. These factors influence the nucleus tractus solitarius, causing its noradrenergic projections to midbrain and forebrain structures to inhibit activity within the ARAS, resulting inactivation of inhibitory GABAergic thalamocortical projections to the cor-tex. During a state of decreased activation, the cortex exhibits a pattern of synchronized EEG. Transition between orthodox sleep and paradoxical sleep is controlled by noradrenergic neurons within the loci coeruleus and serotoninergic neurons within the raphe called REM-off cells and cholinergic neurons within the nucleus reticularis pontis oralis called REM-on cells. Other brain structures are involved in generation and control of REM sleep-related phenomena, like eye movement and muscle atonia.