Sleep Physiology

1. PHYSIOOGY OF SLEEP
FATIMA WAHID MANGRIO
fatimawahid1234@gmail.com

2. Sleep
• Sleep is a state of altered
consciousness or partial
unconsciousness from which an
individual can be aroused. Although it
is essential, the exact functions of
sleep are still unclear.

3. • Sleep deprivation impairs attention,
learning, and performance. Normal
sleep consists of two components:
non-rapid eye movement
(NREM)sleep and rapid eye
movement (REM) sleep. NREM sleep
consists of four gradually merging
stages:

4. • 1. Stage 1 is a transition stage between
wakefulness and sleep that normally lasts
1–7 minutes. The person is relaxed with
eyes closed and has fleeting thoughts.
People awakened during this stage often
say they have not been sleeping.

5. • 2. Stage 2 or light sleep is the first
stage of true sleep. In it, a person
is a little more difficult to awaken.
Fragments of dreams may be
experienced, and the eyes may
slowly roll from side to side.

6. • 3. Stage 3 is a period of moderately
deep sleep. Body temperature and
blood pressure decrease, and it is
difficult to awaken the person. This
stage occurs about 20 minutes after
falling asleep.

7. • 4. Stage 4 is the deepest level of
sleep. Although brain metabolism
decreases significantly and body
temperature drops slightly at this
time, most reflexes are intact, and
muscle tone is decreased only
slightly. When sleepwalking occurs,
it does so during this stage.

8. • Typically, a person goes from stage 1 to
stage 4 of NREM sleep in less than an
hour. During a typical 7- or 8-hour sleep
period,there are three to five episodes of
REM sleep, during which the eyes move
rapidly back and forth under closed
eyelids.

9. • Usually, REM sleep happens 90
minutes after you fall asleep. The
first period of REM typically lasts 10
minutes. Each of your
later REM stages gets longer, and the
final one may last up to an hour.

10. • Then, another interval of NREM
sleep follows. REM and NREM sleep
alternate throughout the night.

11. • Several physiological changes occur
during sleep. Most dreaming occurs
during REM sleep.
• Most somatic motor neurons are
inhibited during REM sleep, which
decreases muscle tone and even
paralyzes the skeletal muscles. Many
people experience a momentary
feeling of paralysis if they are
awakened during REM sleep.

12. • During sleep, activity in the
parasympathetic division of the
autonomic nervous system (ANS)
increases while sympathetic
activity decreases. Heart rate and
blood pressure decrease during
NREM sleep and decrease further
during REM sleep.