Understanding Sleep

Understanding Sleep

Sleep is an integral part of our life. It is crucial for the functioning and restoration of the body. It is a partially-conscious state, regulated by a sleep center in the brain, the Suprachiasmatic nucleus(SCN) in Hypothalamus. It affects the circadian rhythm to regulate sleep. The more you are awake, the stronger is the sleep drive. 

Two basic types of sleep are – Rapid eye movement (REM) sleep and Non-rapid eye movement (NREM) sleep. Adults have four stages of sleep: NREM 1-2-3 and REM. During sleep, one goes through around 4-6 sleep cycles, and each sleep cycle consists of 1-2-3 stages of non-REM and REM sleep. Each cycle lasts about 90 minutes. In the first sleep cycle, REM sleep is of shorter duration. It keeps getting longer with each subsequent sleep cycle.

Stages Of Sleep Cycle

  • NREM 1 Sleep StageStage of sleep transition.
    • It is of a shorter duration. It is like when you are sleepy but aware of your surroundings. Stage of falling asleep.
  • NREM 2 Sleep StageStage of light sleep.
    • Heart rate and body temperature lower, muscles start to relax.
  • NREM 3 Sleep StageStage of deep Sleep.
    • The parasympathetic nervous system starts working in this stage by decreasing body temperature, heart rate, and blood pressure. It is of longer duration in the first cycle of sleep and keeps on decreasing in further cycles. It is crucial for the strengthening of the immune function and the regeneration-repair of body tissues. During this stage of the sleep cycle, growth hormone functions at its peak.
    • Difficult to wake up someone from this stage of the sleep cycle.
  • REM Sleep StageStage of Dreaming.
    • It is the stage during which muscles of the limbs are temporarily paralyzed. Only muscles of the eyes and diaphragm are active. It can go up to an hour in later sleep cycles.
    • Maximum dreaming occurs in this stage of sleep.
    • Heart rate and blood pressure increase.
    • REM sleep is crucial for memory consolidation and learning. It has a significant role in brain development in the pediatric population.

Sleep is influenced by stress, medical conditions, medications, alcohol, caffeine, food intake, hydration levels, fatigue, and age. Sleep deprivation predisposes one to cardiovascular disorders, type 2 diabetes, hypertension, weakened immune system, mood disorders, and obesity.

Common Sleep Disorders

  • Insomnia- Trouble falling asleep.
  • Obstructive Sleep Apnea- Due to blockage of the upper airway tracts.
  • Restless Leg Syndrome- Unpleasant sensations like tingling in the leg make you move your legs to get relief.
  • Narcolepsy-Chartarized by suddenly falling asleep during the daytime. Direct falling into REM sleep.
  • Snoring.

Consult your doctor if you are experiencing any of the above common sleep problems. Polysomnography is a test used to diagnose sleep disorders. 

Sleep is vital for the body to re-energize, detoxify, metabolize and learn. So, have a good night’s sleep for good health.


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