True about REM sleep-

Ans. is 'a' i.e., Paradoxical sleep* Sleep is basically divided into two phases:-A) Non-REM (NREM) or slow-wave sleep:# It is called Non-REM sleep because no rapid eye movement (REM) is there on eletrooculogram, rather there is slow or quiscent eye movement# It is also referred as S-sleep (synchronized sleep) or quiet sleep or orthodox sleep because there is diminished physiological functions and a low level of overall activity.# It is further divided into: -1) Stage 1:* It is a transition from wakefulness to sleep and is characterized by disappearance of alpha activity and appearance of theta activity. There is slow eye movements.2) Stage 2:* It is characterized by typical EEG activity i.e., Sleep spindles and 'K-complex'. No eye movement occurs.3) Stage 3 & 4:* Stage 3 & 4 are stages of deep sleep. These are also called slow wave sleep as these stages are characterized by slow delta waves. Delta wave appearance starts in stage 3 and dominated in stage 4.B) REM sleep:# The REM sleep is so named as there is rapid roving movements of eye, i.e., rapid eye movement (REM) on electro-oculogram.# It is also called paradoxical sleep because there is a paradoxical elevation of brain activity & metabolism and physiological activity.# The high-amplitude slow waves seen in stage 3,4 of REM sleep is replaced by rapid low voltage activity (Beta wave).# Features of REM sleep are: -i) EEG - Beta-wave, Reappearance of alpha wave, Saw-tooth wave (low voltage fast activity), Ponto- genital-occipital spikes.ii) Dreamingiii) Other features :- Generalized muscular atony, Penile erection, autonomic hyperactivity (Increased pulse rate & BP,) and intermittent movement of small muscle groups.