MR.BESTHA CHAKRAPANI M.pharm Associate Professor Department of Pharmacology Balaji College Of Pharmacy Ananthapuramu

1. Sleep cycle
MR.BESTHA CHAKRAPANI M.pharm
Associate Professor
Department of Pharmacology
Balaji College Of Pharmacy
Ananthapuramu

3. Sleep cycle
The sleep cycle is an oscillation between the slow-
wave and REM (paradoxical) phases of sleep.
 It is sometimes called the ultradian sleep cycle,
sleep–dream cycle, or REM-NREM cycle, to
distinguish it from the circadian alternation between
sleep and wakefulness.
 In humans this cycle takes 1–2 hours.

4. Delta wave activity, correlating with slow-wave
(deep) sleep, in particular shows regular
oscillations throughout a good night’s sleep.
Secretions of various hormones, including renin,
growth hormone, and prolactin, correlate positively
with delta-wave activity, while secretion of thyroid-
stimulating hormone correlates inversely.
Heart rate variability, well-known to increase
during REM, predictably also correlates inversely
with delta-wave oscillations over the ~90-minute
cycle.

6. Electroencephalography readily shows the timing of
sleep cycles by virtue of the marked distinction in
brainwaves manifested during REM and non-REM
sleep.
Rapid eye movement sleep (REM sleep, REMS)

15. Homeostatic functions, especially thermoregulation,
occur normally during non-REM sleep, but not
during REM sleep.
Thus, during REM sleep, body temperature tends to
drift away from its mean level, and during non-REM
sleep, to return to normal.
Alternation between the stages therefore maintains
body temperature within an acceptable range.

16. Researchers have proposed different models to
elucidate the undoubtedly complex rhythm of
electrochemical processes that result in the regular
alternation of REM and NREM sleep.
 Monoamines are active during NREMS but not
REMS, whereas acetylcholine is more active during
REMS. The reciprocal interaction model proposed
in the 1970s suggested a cyclic give and take
between these two systems.
 More recent theories such as the "flip-flop" model
proposed in the 2000s include the regulatory role of
in inhibitory neurotransmitter gamma-aminobutyric
acid (GABA).

25. Thank
you