Part 2 - The Principles of Sleep

Here’s a brief overview of the processes that take place every night.

The Sleep Cycle

Sleep may feel like a period of sustained inactivity but the reality couldn’t be further from the truth. By monitoring the brain’s electrical activity, sleep experts have identified that the brain goes through a number of different stages as part of a cycle lasting approximately 90 minutes.Brain activity changes regularly over the course of a night and it is possible to separate these out into 4 different stages of non-rapid eye movement sleep (non-REM sleep) and rapid-eye movement sleep (REM sleep). Each stage of sleep can take up to 90 minutes to complete. To ensure that you wake feeling well rested, an individual should experience all 4 of these phases and preferably 5 or 6 stages overall.

The Circadian Rhythm

The circadian rhythm or “body clock” is the internal 24-hour monitor that regulates periods of wakefulness and sleepiness.It is the circadian rhythm that controls when people feel most alert during the day and when they feel the need to catch up on shut-eye. It also regulates the timings of a number of biological and physiological processes in response to light in the morning and darkness at night.The first piece of advice for any individual in need of better sleep is to listen to their body’s needs and resting when they feel tired.

Growth and recovery

During sleep the body releases a number of hormones involved in muscle growth, tissue repair and protein synthesis. This ensures that the body recovers from the day before and is prepared for the day ahead. The restorative nature of quality sleep also helps to strengthen the immune system so that it is more capable of fighting off infections.

The Glymphatic Clearance Pathway

Memory consolidation isn’t the only thing going on during sleep. It is also the time during which the brain is cleaned through what is known as the glymphatic clearance pathway. Cerebrospinal fluid brings essential nutrients to the central nervous system during this time and washes away neurotoxic waste from the brain and spinal column.

Achieving quality sleep

A truly restorative night’s sleep is achieved when all of the processes above take place without interruption. Simply lying in bed for 8 hours is not the same as enjoying a genuinely good night’s rest.

Sleep scientists use three indicators to assess sleep. These are:

• Sleep onset latency – how fast an individual falls asleep after climbing into bed and turning out the lights

• Sleep efficiency – how much of an individual’s time in bed is spent asleep

• Sleep enjoyment – how an individual feels upon waking up

The results of sleep enjoyment can include elevated mood, reduced stress and higher energy levels – all factors that will improve performance for the day ahead and make the following night’s sleep more likely to be a good one.

Stages of Sleep
Stages 1&2 (NON REM)
These first two stages of sleep are relatively light and it is possible to be woken easily during these phases.
Stage 3(NON REM)
Sleep becomes deeper and it is more difficult for a sleeper to be roused. When woken suddenly from this phase of sleep an individual typically feels disorientated and groggy.
Stage 4 (REM)
REM sleep is quite different to the other stages of sleep. During REM sleep your brain’s electrical activity increases to levels similar to those you experience while awake. It is during REM sleep that dreams occur and memories are consolidated as brain repair takes place.

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