Have you ever wondered how your sleep is regulated and what is responsible for regulating your internal clock? What exactly is the reason you so often wake up right before your alarm clock or what makes you tired at night?
Your suprachiasmatic nucleus is the brain structure responsible for regulating your sleep-wake cycles. It receives information from the pineal gland, releasing melatonin (your “sleepy” hormone) when environmental levels of light are low.
There’s no way around it: Getting good sleep is fundamental to your well-being. It can help you regulate stress hormones and you will feel greater rewards from out of your exercise session (i.e. with a better sleep you will be able to experience a much greater Exercise High). That’s why I consider it one of the pillars of health. Yet, even knowing this, so many people neglect sleep.
How Your Sleep is Regulated
– A Deeper Look
Next, let us dive deeper into our brains to see what structures are involved in inducing a restful sleep, as well as learn how structured and organized our sleep actually is. This will help us to better understand how the tools discussed later in this chapter aid in providing us with the quality and quantity of sleep that we require.
The “Master Clock”
What mechanism controls our sleep? What is responsible for our wakefulness and what is it that signals us to go to sleep at night? Our sleep patterns are governed by something known as circadian rhythms (circa, which means “around,” and dian, which means “day”). These rhythms are the day–night cycles naturally generated by virtually every living creature on earth. As chaotic as sleeping may at times seem, it is actually quite an organized and structured process.
Your circadian rhythms are like your personal internal clock, a clock that is directly influenced by environmental cues—particularly light—and works by helping to make sure that the body’s processes are optimized at various points during each 24-hour period.
How it Works
A small part of your brain called the Suprachiasmatic Nucleus, also referred to as the “Master clock”, receives information about the environmental light levels. This information is relayed to your pineal gland and tells it how much melatonin to produce and release into the bloodstream. Melatonin is a hormone that regulates our sleep-wake cycles.
An increased production of melatonin will help to induce sleep, while low amounts of melatonin within the bloodstream promote wakefulness. Your suprachiasmatic nucleus acts as the central processing center that regulates how much melatonin is released and therefore determines your wakefulness.
Everyone has a circadian rhythm. Just about every region of your brain and every organ in your body receive daily signals from your brain’s internal clock. These signals direct a host of functions, such as helping your endocrine system know how many stress hormones to produce (production is typically highest in the afternoon hours), regulate your body temperature, and reminding you when it’s time to eat breakfast and dinner.
Your internal clock is what causes you to get tired at specific hours during the day, and is also the reason it may take you a week to get over jet lag (our internal clock is only able to adjust about 30 to 60 minutes a night).
How Your Sleep is Regulated
– 90-Minute Sleep Cycles
Once you lose consciousness late at night, you don’t simply just sleep; you pass through several 90-minute sleep cycles during the course of the night, and each of these cycles contains two distinct stages of sleep. The names given to these sleep stages were based on their distinguishing eye movements: non–rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep.
As you can tell from the figure below, there is a constant ebb and flow between both stages across a given sleep cycle. It has been shown that we require about five to six sleep cycles each night in order to be well rested for the following day.
REM Sleep
REM sleep is the stage associated with dreaming and memory consolidation. You experience your first round of REM sleep approximately 60–90 minutes into the night. During REM sleep, your heart rate increases, your breathing becomes erratic, and your eyes move quickly behind your closed eyelids.
Your brain is quite active during REM sleep, and your brain waves become more erratic, which is in contrast to other stages of sleep, during which your brain waves settle down. During REM sleep, your body functions largely the same way as it does while you’re awake, with the exception that your eyes are closed and you temporarily lose your muscle tone. This is hypothesized to be a protection mechanism, designed to prevent you from acting out your dreams and hurting yourself and others around you while you’re asleep.
NREM Sleep
NREM sleep is a little different. It is characterized by three distinct phases. Various body processes slow down or cease entirely as you cycle through the three NREM sleep stages, allowing reparative and restorative processes to take over.
During stage 3 NREM sleep, the deepest phase of sleep, your heart rate, respiration, muscular activity, and brain waves are all at their lowest points. In this phase, the body repairs muscle, bone, and tissue while releasing growth hormone. This deep sleep aids in the control of memory, hormone release, immune system activity, and energy metabolism.
Did you ever notice the huge difference in your overall well-being after enjoying consistent, uninterrupted each night for a whole week? I hope that diving deeper into the anatomy and physiology of the processes involved in our sleep helps you to gain an appreciation of what is occurring within your brain to induce sleep and to keep you asleep. On top of that, I hope that it highlights the importance of promoting an uninterrupted sleep and a consistent bed-time routine in mood regulation.
Are You Sleeping Well?
Now that you understand the reasons we sleep, as well as some of the basic science, let us analyze your sleep. First off, let’s state the fairly obvious: You will reap the greatest benefits from sleep when you get enough hours of sleep each night (you cannot consistently cheat yourself on sleep quantity and hope to maintain your well-being), have sleep that is relatively uninterrupted, and maintain a consistent sleep schedule suiting your natural circadian rhythms.
Calculating your biological prime time will help you find out the best times to go to bed for maximum productivity and provide you with insight as to when your best hours to be productive may be. By the way, one of my favorite sleep researchers is Matthew Walker. I highly recommend that you go and check out his website to learn more about how a better sleep can be the key to good health.
Knowing this, do you still find yourself regularly struggling with getting enough quality sleep? If so, let us go over the signs (what is observable) and symptoms (your feelings) of a bad sleep. Noticeable physical signs that you are not sleeping well include skin breakouts (e.g., acne), red and swollen eyes, dark circles beneath your eyes, and weight gain within a short period of time.
Self Test
Moving on from observable physical signs of poor sleep, let’s examine your subjective feelings related to sleep:
- Are you waking up rested in the morning? Do you feel rested or could you sleep for another 30 to 60 minutes? In addition, do you experience a sore throat, dry mouth, or headaches upon waking?
- How energized do you feel during the day? Quick drops in energy levels throughout your day may be a sign that you are not getting an efficient enough night’s sleep.
- What is your mood like during the day? Sleep helps to regulate our hormones, which helps us to keep a stable mood throughout the day. So if you find yourself having a lot of mood swings and suffer from symptoms of anxiety and depression, it may be worth analyzing your sleep routine.
- Do you feel clear-headed throughout your day? Good quality sleep helps us process stressful events that happen during the day. If we do not get a restful sleep, we feel more stressed as we have more on our mind. Our cognitive performance (our focus and memory) suffers, in addition to having unprocessed thoughts and ideas from the day before.
What foods/drinks do you crave during your day? If you have increased cravings for junk food or for drinks containing caffeine, then this might be a sign that you have not been sleeping well.
There you have it. I hope that this article helped you gain a better understanding of how sleep works and analyze your sleep patterns. How do you feel after a night’s rest?