Sleep Cycles: What Are They? Why Is It Important To Know About Them?

No, sleep cycles are not exercising gadgets that you do workouts with in the night. To understand what they are and the role they play in the upkeep of mental and physical health, you might have to start with an understanding about stages of sleep.

Stages of sleep and their link to sleep cycles 

There are two types of sleep, the Non-REM and REM, where REM stands for Rapid Eye movement. Sleep consists of four phases of NON-REM and REM stages during which a host of activities happen that keep our mind and body healthy and help us remain alert and productive.

The characteristic features of these stages are:

–          Each stage is different in terms of their contribution to mental and physical health.

–          Time spent in each phase alters during the course of the night.

Sleep transition: from onset to dream phase and back 

When we fall asleep, we are entering the NREM stage of sleep; the entry point is stage 1 (transition to sleep) which lasts for about 4 minutes. We enter stage 2 or light sleep, the true stage of true sleep, which lasts for 10 to 25 minutes. Stage 3 is deep sleep stage from where it is tough to wake up.

The REM or dream phase begins after about 70 to 90 minutes after falling asleep.

Sleep follows a specific pattern during the night, involving recurrent alteration between deep restorative sleep stage (non-REM) and more alert or dream sleep called REM sleep. Sleep cycles are sets of non-REM and REM stages of sleep put together. Each sleep cycle usually lasts for about 90 minutes or so, and recurs four to six times during the night.

What kind of impact do sleep cycles have on the different physiological processes? 

To begin with, here is a comparative chart of what happens to different body functions during the REM and non-REM stages of sleep:

Comparison of Physiological Changes during NREM and REM Sleep 

Physiological Process During NREM During REM
brain activity decreases from wakefulness increases in motor and sensory areas, while other areas are similar to NREM
heart rate slows from wakefulness increases and varies compared with NREM
blood pressure decreases from wakefulness increases (up to 30 percent) and varies from NREM
blood flow to brain does not change from wakefulness in most regions increases by 50 to 200 percent from NREM, depending on brain region
respiration decreases from wakefulness increases and varies from NREM, but may show brief stoppages (apnea); coughing suppressed
airway resistance increases from wakefulness increases and varies from wakefulness
body temperature is regulated at lower set point than wakefulness; shivering initiated at lower temperature than during wakefulness is not regulated; no shivering or sweating; temperature drifts toward that of the local environment
sexual arousal occurs infrequently increases from NREM (in both males and females)

Link between sleep cycles and body functions

–          Impact on endocrine system: sleep is not just a restful event. Production of several hormones take place during sleep including growth hormone for facilitating repair processes; Follicle stimulating hormone and luteinizing hormone involved in female reproductive processes; luteinizing hormone that initiates puberty.

–          Effect on the kidneys: kidney filtration, excretion of sodium, chloride, potassium, and calcium are diminished during both NREM and REM sleep.

–         Gastric system: Gastric acid secretion is reduced during sleep for a healthy individual.

Leave A Response

* Denotes Required Field