This is Why I Sleep - Sleep Science

Sleep is such an important physiological function and is often overlooked or not considered when discussing health and wellbeing. When writing This is Why I Sleep I was inspired by scientific backed physiological concepts of sleep. The book is a fun way to portray these concepts and creates an opportunity for learning at bedtime.  Below is a list of descriptions of the physiological concepts portrayed in This is Why I Sleep.

Do we actually grow when we sleep?

Yes, sleep plays an important role in our physical growth, particularly during childhood and adolescence. During sleep our pituitary gland releases growth hormone (GH). This hormone stimulates muscle repair, tissue regeneration, and bone growth.

Sleep Acts as an Overnight Power Cleanse for Our Brain.

Throughout the day our brains are working to create typical functions and the experience of life. As the brain burns energy it creates metabolic waste products that accumulate in our brain. During sleep, our brain flushes this waste product away by means of the glymphatic system.

The glymphatic system is like our lymphatic system, but in our brains instead of our body.  Its primary role is to remove waste from the brain. When the glymphatic system is active, cerebrospinal fluid (CSF) floods the perivascular spaces around the arteries where it mixes with interstitial fluid (ISF). The fluid collects the metabolic waste products and is eventually drained through the cervical lymphatic vessels.

Glial cells (brain supporting cells) such as astrocytes assist in the glymphatic system by assisting in the exchange in fluid. When we sleep some glial cells will shrink up to 60% to allow more space for fluid flow or “flush”.  

The glymphatic system is found to be much more active during sleep than during waking hours and is most active during stages 3 and 4 of deep NREM sleep, which occurs earlier in the night.

When we sleep our brains also clear a chemical called adenosine. Adenosine is responsible for the heavy sleep pressure feeling we get when we are tired. The longer we are awake the more adenosine builds up. The buildup of adenosine plays a crucial role in assisting in the timing of our sleep.

Fun Fact: Caffeine blocks the adenosine receptors, making us feel less tired, but adenosine continues to build up and creates even more sleepiness when the caffeine wears off (caffeine crash).

Sleep’s Role in Memory and Learning

Sleep plays an important role in memory processes. The consolidation of short-term memories into long-term memory occurs during sleep. By clearing the hippocampus (area of the brain involved in short-term memory and other memory processes) of short-term memories, it not only creates long-term memories, but also creates more space for working and short-term memories for the following day. This process restores our brain’s capacity for learning and is why adequate sleep before learning is important. The consolidation of memories is thought to occur during our deeper NREM sleep. REM sleep is thought to integrate memories, link them together, and facilitate creativity.

Sleep also plays an important role in motor learning and learning new skills. Motor skills such as playing instruments, swinging a golf club, or a baby learning to stand strengthen during REM and light NREM sleep. When we sleep our brain continues to the learning process and helps strengthen the neural connections needed to perform the skill accurately.

Sleeps Role Physical Performance and Exercise Tolerance

Sleep has been shown to boost physical performance in athletes. Studies have shown that athletes who get more sleep show improved speed, accuracy, reaction time, and stamina. Sleep deprivation will not only result in decreased performance but also increase perceived effort during exercises. Basically, you’re going to feel tired faster and not be able to perform as much or as intense of exercise. This is due to reduced cardiovascular efficiency and shoes increased resting hear rates, increases in blood pressure, and decrease in heart rate variability. These factors can put increased strain on the heart and decrease VO2 max.

Sleep, particularly deep NREM sleep, assists in muscle repair, tissue regeneration, and bone strengthening. In conjunction, sleep will also decrease your risk of injury. Studies have shown that athletes who sleep less than six hours a night are significantly more likely to get injured. Adolescent athletes who got less than eight hours of sleep were found to be 1.7 times more likely to get injured.

Sleep and Emotion and Psychological Health

Sleep plays a crucial role in regulating emotional states and our general mental health. REM sleep helps us process emotional experiences. During REM sleep we can revisit emotional events, but with lower levels of stress hormones, which allows us to process them more calmly. When sleep deprived our amygdala (brain region responsible for fear) is more active and has decreased communication with our pre-frontal cortex (brain region for ration and reason). Sleep deprivation has been shown to significantly increase the risk of depression and anxiety disorders.

Sleep has been shown to increase our ability to empathize and interpret others’ emotions, which will increase our ability to have healthy social lives. Sleep also has been found to increase mental resilience to stress. It can improve our creative problem-solving, emotional stability, and psychological flexibility.

Sleep and Healthy Physiological Function

Sleep helps regulate many physiological functions. Sleep helps improve cardiovascular health, assist in regulating blood sugar, and helps prevent and fight against cancer.