1️⃣Sleep is regulated by two biological mechanism, which is circadian rythm and homeostatis, that work together to regulate our sleep and wake cycle. To undestand how do we sleep we need to understand this two mechanism.

 

2️⃣Circadian rythms

Direct a wide variety of functions from daily fluctuations in wakefulness to body temperature, metabolism, and the release of hormones.  They control your timing of sleep and cause you to be sleepy at night and your tendency to wake in the morning without an alarm.  Your body’s biological clock, which is based on a roughly 24-hour day, controls most circadian rhythms.  Circadian rhythms synchronize with environmental cues (light, temperature) about the actual time of day, but they continue even in the absence of cues.

 

3️⃣Sleep-wake homeostasis

Keeps track of your need for sleep.  The homeostatic sleep drive reminds the body to sleep after a certain time and regulates sleep intensity.  This sleep drive gets stronger every hour you are awake and causes you to sleep longer and more deeply after a period of sleep deprivation.

 

4️⃣Another factors that influence sleep and wake cycle are medical conditions, medication, stress, sleep environtment, food, and exposure to light. Exposure to light is the greatest influence, because speciallized cells in retinas process light and give information to brain whether it is day or night so it can delay or advance our sleep cycle.

 

5️⃣Sleep has a typical underlying architecture characterized by arhythmic alternation between NREM and REM stages. NREM are divided by 4 stages, which is 75% of our sleep and REM consist of 25% of our sleep.

 

Artist: @lim_xiao_xi 

Educator: @bastantarie 

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