Sleep is as essential for good and healthy life as we need proper food and other important survival conditions. Sleep basically affects our physical and mental health in many ways.

NEUROTRANSMITTERS INVOLVED WITH SLEEP

The basic neurotransmitters involved with sleep are acetylcholine, norepinephrine, and serotonin. Which are called the nerve signaling chemicals and they control whether we are asleep or awake by acting on different groups of nerve cells, or neurons, in the brain. Neurotransmitters such as serotonin and norepinephrine keep some parts of the brain active while we are awake when the neurons in the brain stem connect with the spinal cord. While other neurons of the brain start signaling while we fall asleep and switch off the active neurons of the brain. When we awake than the usual the body gives signals by secreting chemical called adenosine which makes us drowsy and gradually breaks down when we sleep off.

SLEEP CYCLES

Sleep is divided into ninety-minute cycles of rapidly alternating REM and non-REM sleep.
REM is rapid eye movement and it includes four stages. During stage 1, which is light sleep, we drift in and out of sleep and can be awakened easily. Our eyes move very slowly and muscle activity slows. People awakened from stage 1 sleep often remember fragmented visual images. , someone being awoken from Stage One sleep will often be unable to sleep until 2-3 hours later.

In Stage Two sleep, there is increasingly deepening sleep, When we enter stage 2 sleep, our eye movements stop and our brain waves becomes slower, With occasional bursts of rapid waves called sleep spindles. Brain waves are the variations of electrical activity that happens in the brain and are measured by electrodes with occasional bursts of rapid waves called sleep spindles.
In stage 3, delta waves begin to appear which is extremely slow brain waves intermingled with faster waves. By stage 4, the brain produces delta waves totally. It is very difficult to wake someone during stages 3 and 4, which together are called deep sleep. There is no eye movement or muscle activity present here. People don't easily wake up from this state of sleep. Little children often do bedwetting, sleepwalking and nightmares during this part of sleep. Extremely slow brain waves called delta waves begin to appear, interspersed with smaller, faster waves. By stage 4, the brain produces delta waves almost totally. It is very difficult to wake someone during stages 3 and 4, which together are called deep sleep. There is no eye movement or muscle activity. People awakened during deep sleep do not adjust immediately and often feel groggy and disoriented for several minutes after they wake up. It is very difficult to wake someone during stages 3 and 4, which together are called deep sleep. Movement is typically not possible in REM sleep, although sleepwalking is possible in REM sleep with younger individuals. Dreams often occur during REM sleep.

The first sleep cycle is often non-REM.we then switch to REM sleep. Changes include irregular, and rapid, breathing. Eyes move rapidly and our limb muscles become temporarily paralyzed. Heart rate and blood pressure rises. There is a low probability of REM in early sleep, but as sleep progresses, non-REM sleep becomes less prevalent. Therefore, the longer the sleep, the larger the percentage of REM to non-REM sleep is found at the end. By the end of the sixth sleep cycle (approximately 9 hours of sleep), there is 50% REM sleep to 50% non-REM sleep.

ELECTRICAL ACTIVITY

Electrical activity of sleep can be measured by electroencephalogram (EEG).In this method an EEG electrode is placed on the head, which record the electrical waves.
Sleep is characterized by three electrical waves on:
• Alpha waves - Associated with relaxed consciousness, occur approximately 10 minutes before sleep. Fairly high frequency of 8-13 hertz.
• Delta waves - Associated with sleep, high amplitude and synchronous.
• Theta waves - Associated with deeper sleep, higher amplitude and synchrony.

WHAT DOES SLEEP DO FOR US?

Studies show that sleep is necessary for survival. Sleep deprivation affects the immune system in detrimental ways. Sleep is necessary for our nervous systems to work properly. Little sleep leads to impaired memory hallucinations and mood swings may also develop. During sleep neutrons get chance to repair themselves else they will begin to malfunction. Good sleep may help people maintain optimal emotional and social functioning while they are awake. And are also shows with higher production of proteins.
Sleep Disorders may include Insomnia, Sleep, Restless, and Narcolepsy

HOW MUCH SLEEP DO WE NEED?

The amount of sleep needed by individuals vary from person to person and from age group to another. Like infants need 16 hours a day and teens need 9 hours of sleep while adults need 7 to 8 hours.

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