Table 2. Characteristics of NREM and REM sleep.

Characteristic	NREM	REM
Proportion of sleep cycle	75-80%	20-25%
Ability to arouse	Easy	Difficult
Airway resistance	Increases from wakefulness	Increases and varies from wakefulness
Respiration	Decreases	Increases; coughing suppressed; may show brief stoppages
Muscle tone	Muscular activity	No movement
Heart rate	Decreases	Increases
Blood pressure	Decreases	Increases
Sympathetic nerve activity	Decreases	Increases
Blood flow to brain	Decreases	Increases (dependent on brain region)
Brain activity	Decreases	Increases in motor and sensory areas
Body temperature	Regulated at lower set point	No regulation

All in reference to state of wakefulness. NREM, non-rapid eye movement; REM, rapid eye movement.