Sleep is a state of unconsciousness from which person can be aroused by appropriate sensory or other stimuli.
It is a state of unconsciousness from which person cannot be aroused by external stimuli.
CNS changes during sleep:
- Somatic activity is depressed.
- Superficial reflexes are unchanged, except plantar reflex that becomes Babinski’s sign.
- Deep reflexes are reduced.
- Vasomotor reflexes (any reflex response of the circulatory system) are brisk.
- If we do EEG (Electro-Encephalo-Gram) of brain it shows Gamma waves and also sleep spindles.
Physiological changes during sleep:
- Cardiovascular pulse rate, vasomotor tone, cardiac output and blood pressure are all decreased.
- Muscles are relaxed.
- Eye balls moves up and out and constriction of pupil occurs.
- Some Hormones level raised.
- Salivary and lacrimal secretions decreases; while gastric and sweat secretions increases.
- Respiration is slow.
- Basal metabolic rate is reduced up to 10-15%
- Urine volume decreases.
- Blood volume increases.
Normal Sleep requirements:
New born = 16-20 hr/day
Children = 12-14 hr/day
Adults = 7-9 hr/day
Old age = 5 hr/day
Types of sleep:
Investigators now believe that there are two types of sleep.
1) Non-REM Sleep (slow wave sleep)
2) REM Sleep
Non-REM Sleep (slow wave sleep)
This is Non-rapid eye movement sleep. This is the deep and restful type of sleep characterized by decreases in peripheral vascular tone, blood pressure, respiratory rate, and basal metabolic rate. Dreams can occur during slow wave sleep but they are not remembered. Non-REM and REM sleep alternate with each other.
This is rapid eye movement sleep. In this sleep brain is quite active and skeletal muscle contraction occurs hence it is called Paradoxical Sleep. Your eyes moves under your eyelids in REM sleep. REM sleep lasts 5-30 minutes and repeats at approximately 90 minute intervals.
There are several important features of REM sleep.
1) Dreaming occurs and the dream can be recalled.
2) Waking a person in REM sleep is more difficult.
3) REM sleep comes after Non-REM sleep.
4) Both heart rate and respiratory rate become irregular.
5) Brain is quite active in this type of sleep so brain metabolism is increased to about 20%
6) Muscle tone is depressed.
7) Muscle contraction will occur despite the decreased muscle tone.
Benefits of Sleep:
- Sleep improves the memory.
- It strengthens the immune system.
- Sleep restores the normal balance of activity in the brain and thus make you more alert.
- Sleep reduces the risk of having depression.
- Sleeps also regulates your blood pressure and respiratory rate as well.
- Take 1 glass of water before sleep it avoids stroke or Heart Attack.