Brain Basics: Understanding Sleep | National Institute of Neurological Disorders and Cerebrovascular Accidents (2023)


Brain Basics: Understanding Sleep | National Institute of Neurological Disorders and Cerebrovascular Accidents (1)

Sleeping is an important part of your daily routine – you spend about a third of your time sleeping. Good sleep and getting enough sleep at the right time are just as important to survival as food and water. Without sleep, you can't form or maintain the pathways in your brain that allow you to learn and create new memories, and it's harder to focus and react quickly.

Sleep is important for a range of brain functions, including how nerve cells (neurons) communicate with each other. In fact, your brain and body are remarkably active while you sleep. Recent evidence suggests that sleep plays a cleansing role, flushing out the toxins in your brain that build up during waking hours.

Everyone needs sleep, but its biological purpose remains a mystery. Sleep affects nearly every type of tissue and system in the body, from the brain, heart, and lungs to metabolism, immune function, mood, and disease resistance. Research shows that chronic sleep deprivation or poor sleep quality increases the risk of conditions such as high blood pressure, cardiovascular disease, diabetes, depression and obesity.

Sleep is a complex and dynamic process that affects how sleep works in ways that scientists are just beginning to understand. This booklet describes how your need for sleep is regulated and what happens in your brain during sleep.

anatomy am me

Several structures in the brain are involved in sleep.


Brain Basics: Understanding Sleep | National Institute of Neurological Disorders and Cerebrovascular Accidents (2)

HimHypothalamus, a peanut-sized structure deep in the brain, contains clusters of nerve cells that act as control centers that affect sleep and wakefulness. Within the hypothalamus is theSuprachiasmatischen Nucleus(SCN): Groups of thousands of cells that receive information about exposure to light directly from the eyes and control their rhythm of behavior. Some people with SCN disrupt sleep irregularly during the day because they cannot synchronize their circadian rhythm with the light-dark cycle. Most blind people retain some ability to perceive light and can alter their sleep-wake cycles.

Himbrainstem, at the base of the brain, communicates with the hypothalamus to control the transitions between wakefulness and sleep. (The brainstem includes structures called the pons, medulla, and midbrain.) Sleep-promoting cells within the hypothalamus and brainstem produce a brain chemical calledGABA, which reduces the activity of the excitatory centers in the hypothalamus and brainstem. The brainstem (particularly the pons and medulla) also plays a special role in REM sleep; It sends signals to relax the muscles that are essential for posture and limb movement, so we don't act out our dreams.

HimThalamusActs as a relay of information from the senses to thecerebral cortex(the covering of the brain that interprets and processes information for short-term and long-term memory). During most stages of sleep, the thalamus is silent, allowing you to shut out the outside world. But during REM sleep, the thalamus is active, sending images, sounds, and other sensations to the cortex that fuel our dreams.

Himpineal gland, located in both hemispheres of the brain, receives signals from the SCN and increases hormone productionMelatonin, which helps you fall asleep when the lights are off. People who have lost their eyesight and cannot coordinate their natural sleep-wake cycle with natural light can stabilize their sleep cycle by taking small amounts of melatonin at the same time each day. Scientists believe that the ebb and flow of melatonin over time is important in aligning the body's circadian rhythm with the external light-dark cycle.

HimProsencephalon basal, located near the front and bottom of the brain, also promotes sleep and alertness while being part of themidbrainworks as an excitation system. The release of adenosine (a chemical byproduct of cellular energy expenditure) from basal forebrain cells and likely other regions supports your sleep drive. Caffeine counteracts drowsiness by blocking the effects of adenosine.

HimAmygdala, an almond-shaped structure involved in processing emotions, becomes increasingly active during REM sleep.

Sleep phases and mechanisms

phases they are

There are two basic types of sleep: Rapid Eye Movement (REM) sleep and non-REM sleep (which has three distinct phases). Each is related to specific brain waves and neural activity. During a typical night, you cycle through all phases of REM and non-REM sleep multiple times, with the REM phases getting longer and deeper in the morning.


Brain Basics: Understanding Sleep | National Institute of Neurological Disorders and Cerebrovascular Accidents (3)

Level 1Non-REM sleep is the transition from wakefulness to sleep. During this brief period (several minutes) of relatively light sleep, your heart rate, breathing, and eye movements slow and your muscles relax with occasional spasms. Your brainwaves begin to slow down from your daytime waking patterns.


Brain Basics: Understanding Sleep | National Institute of Neurological Disorders and Cerebrovascular Accidents (4)

Level 2Non-REM sleep is a phase of light sleep before entering deeper sleep. Heart rate and breathing slow down and muscles relax even more. Body temperature drops and eye movements stop. Brain wave activity decreases but is characterized by brief bursts of electrical activity. You spend more of your repeated sleep cycles in sleep stage 2 than in other sleep stages.


Brain Basics: Understanding Sleep | National Institute of Neurological Disorders and Cerebrovascular Accidents (5)

level 3Non-REM sleep is the deep sleep time you need to feel refreshed in the morning. Occurs in longer periods in the first half of the night. Heart rate and breathing slow to their lowest levels during sleep. Your muscles are relaxed and it may be difficult to wake you up. Brain waves slow down even more.


Brain Basics: Understanding Sleep | National Institute of Neurological Disorders and Cerebrovascular Accidents (6)

REM sleepfirst occurs about 90 minutes after falling asleep. His eyes dart back and forth behind closed lids. The mixed frequency brain wave activity approximates that observed in the waking state. Your breathing will become faster and more irregular, and your heart rate and blood pressure will rise to near-waking levels. Most of your dreams occur during REM sleep, although some can also occur in non-REM sleep. The muscles in your arms and legs become temporarily paralyzed, preventing you from fulfilling your dreams. As you get older, you sleep less in REM sleep. Memory consolidation likely requires both non-REM and REM sleep.

Sound mechanisms

From the internal biological mechanisms– circadian rhythm and homeostasis – work together to regulate when you are awake and when you are asleep.

heart rhythmsThey control a variety of functions, from daily fluctuations in wakefulness to body temperature, metabolism, and hormone secretion. They control when you sleep and make you sleepy at night and your tendency to wake up in the morning without an alarm. Your body's biological clock, which is based on an approximately 24-hour day, controls most of the circadian rhythms. Circadian rhythms are synchronized with environmental cues (light, temperature) over the actual time of day, but continue to run without cues.


Brain Basics: Understanding Sleep | National Institute of Neurological Disorders and Cerebrovascular Accidents (7)

Homeostasis are evetracks your need for sleep. The homeostatic sleep instinct reminds the body to fall asleep after a certain time and regulates sleep intensity. This sleep surge increases with each waking hour, causing you to sleep longer and deeper after a period of sleep deprivation.

Factors that affect your sleep and wake needs include medical conditions, medications, stress, your sleep environment, and what you eat and drink. Perhaps the biggest influence is exposure to light. Specialized cells in the retinas of your eyes process light and tell the brain whether it's day or night, and can speed up or slow down our sleep-wake cycles. Exposure to light can make it difficult to fall asleep and fall asleep again when you wake up.

Night shift workers often have trouble falling asleep at bedtime, and they also have trouble staying awake at work because their natural circadian rhythm and sleep-wake cycle are disrupted. In jet lag, when people fly to a different time zone, the circadian rhythm gets out of step with the time of day, creating a discrepancy between the internal clock and the real clock.

how much sleep do you need


Brain Basics: Understanding Sleep | National Institute of Neurological Disorders and Cerebrovascular Accidents (8)

Your sleep needs and patterns change with age, but this varies significantly between people of the same age. There is no magic "number of hours of sleep" that works for everyone of the same age. Initially, babies sleep between 16 and 18 hours a day, which can stimulate growth and development (especially of the brain). School-age children and adolescents need an average of 9.5 hours of sleep per night. Most adults need 7 to 9 hours of sleep a night, but after the age of 60, nighttime sleep tends to be shorter, lighter, and interrupted by multiple awakenings. Seniors are also more likely to take medications that interfere with sleep.

In general, people get less sleep than they need due to long work hours and 24-hour availability of entertainment and other activities.

Many people think they can "catch up" on lost sleep over the weekend, but depending on how miserable they are, getting more sleep on the weekends may not be enough.

am and monitoring am


everyone dreams You spend about 2 hours every night dreaming, but you may not remember most of your dreams. Its exact purpose is unknown, but dreaming can help you process your emotions. The day's events often invade your thoughts while you sleep, and people suffering from stress or anxiety are more likely to have scary dreams. Dreams can be experienced at all stages of sleep but are generally most vivid during REM sleep. Some people dream in color while others only remember black and white dreams.


Brain Basics: Understanding Sleep | National Institute of Neurological Disorders and Cerebrovascular Accidents (9)

Sleep tracking by smart technology

Millions of people use smartphone apps, bedside monitors, and wearable devices (like bracelets, smartwatches, and headbands) to informally collect and analyze sleep data. Smart technology can record sounds and movements during sleep, log sleep hours, and monitor heart rate and breathing. With a companion app, data can be synced from some devices to a smartphone or tablet, or uploaded to a PC. Other apps and devices emit white noise, produce light that stimulates melatonin production, and use gentle vibrations to help us fall asleep and wake up.

The role of genes and neurotransmitters

chemical signals for sleep

Clusters of sleep-promoting neurons in many parts of the brain become more active as we prepare for sleep. Nerve signaling substances, so-called neurotransmitters, can "turn off" or dampen the activity of cells that signal excitement or relaxation. GABA is associated with sleep, muscle relaxation and calming. Norepinephrine and orexin (also called hypocretin) keep parts of the brain active while we are awake. Other neurotransmitters that shape sleep and wakefulness are acetylcholine, histamine, adrenaline, cortisol, and serotonin.

genes and are

Genes can play a role in how much sleep we need. Scientists have identified several genes associated with sleep and sleep disorders, including genes that control neuron excitability and "clock" genes such asFor,Hour, SheComplainthat affect our circadian rhythm and sleep timing. Genome-wide association studies have identified sites on different chromosomes that increase our susceptibility to sleep disorders. In addition, various genes associated with sleep disorders such as familial advanced sleep phase disorder, narcolepsy and restless legs syndrome have been identified. Some of the genes that are expressed in the cerebral cortex and other areas of the brain change their level of expression between sleep and wakefulness. Several genetic models, including the worm, fruit fly, and zebrafish, are helping scientists identify the molecular mechanisms and genetic variants involved in normal sleep and sleep disorders. Further research will provide a better understanding of inherited sleep patterns and the risks of circadian and sleep disorders.


Brain Basics: Understanding Sleep | National Institute of Neurological Disorders and Cerebrovascular Accidents (10)

sleep studies

Your doctor may recommend a polysomnogram or other test to diagnose a sleep disorder. A polysomnogram usually involves an overnight stay at a sleep laboratory or sleep center. It records your breathing, oxygen levels, eye and limb movements, heart rate and brain waves throughout the night. Your dream will also be recorded on video and audio. The data can help a sleep specialist determine if you're reaching and progressing through the various stages of sleep correctly. The results can be used to develop a treatment plan or determine if further testing is needed.

Tips for a good night's sleep


Brain Basics: Understanding Sleep | National Institute of Neurological Disorders and Cerebrovascular Accidents (11)

Getting enough sleep is good for your health. Here are some tips to improve your sleep:

  • Set a time: Go to bed and wake up at the same time every day.
  • Exercise 20 to 30 minutes a day, but no more than a few hours before bed.
  • Avoid caffeine and nicotine late in the day and alcoholic beverages before bed.
  • Relax before bed: Try a warm bath, reading, or another relaxing routine.
  • Create a bedroom to sleep in: Avoid bright lights and loud noises, keep the bedroom at a comfortable temperature, and don't watch TV or have a computer in the bedroom.
  • Don't lie awake in bed. If you can't sleep, do something else, like reading or listening to music, until you feel sleepy.
  • See a doctor if you have trouble sleeping or feel unusually tired during the day. Most sleep disorders are treatable.

hope through research

Scientists are learning more and more about the function and regulation of sleep. A major focus of research is understanding the risks of chronic sleep deprivation and the relationship between sleep and illness. People who are chronically sleep deprived are more likely to be overweight, have strokes and cardiovascular diseases, infections and certain types of cancer than people who are sleep deprived. Sleep disorders are common in people with age-related neurological conditions such as Alzheimer's disease and Parkinson's disease. Many mysteries remain about the link between sleep and these health issues. Does lack of sleep cause certain disorders or do certain diseases cause sleep deprivation? These and many other questions about sleep represent the limits of sleep research.

Top Articles
Latest Posts
Article information

Author: Terence Hammes MD

Last Updated: 01/18/2023

Views: 6288

Rating: 4.9 / 5 (49 voted)

Reviews: 88% of readers found this page helpful

Author information

Name: Terence Hammes MD

Birthday: 1992-04-11

Address: Suite 408 9446 Mercy Mews, West Roxie, CT 04904

Phone: +50312511349175

Job: Product Consulting Liaison

Hobby: Jogging, Motor sports, Nordic skating, Jigsaw puzzles, Bird watching, Nordic skating, Sculpting

Introduction: My name is Terence Hammes MD, I am a inexpensive, energetic, jolly, faithful, cheerful, proud, rich person who loves writing and wants to share my knowledge and understanding with you.