Chemicals that make you sleep

Brain Basics: Understanding Sleep | National Institute of Neurological Disorders and Stroke


Sleep is an important part of your daily routine—you spend about one-third of your time doing it. Quality sleep – and getting enough of it at the right times -- is as essential to survival as food and water. Without sleep you can’t form or maintain the pathways in your brain that let you learn and create new memories, and it’s harder to concentrate and respond quickly.

Sleep is important to a number of brain functions, including how nerve cells (neurons) communicate with each other. In fact, your brain and body stay remarkably active while you sleep. Recent findings suggest that sleep plays a housekeeping role that removes toxins in your brain that build up while you are awake.

Everyone needs sleep, but its biological purpose remains a mystery. Sleep affects almost 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 a chronic lack of sleep, or getting poor quality sleep, increases the risk of disorders including high blood pressure, cardiovascular disease, diabetes, depression, and obesity.

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

Anatomy of Sleep

Several structures within the brain are involved with sleep.


The hypothalamus, a peanut-sized structure deep inside the brain, contains groups of nerve cells that act as control centers affecting sleep and arousal.  Within the hypothalamus is the suprachiasmatic nucleus (SCN) – clusters of thousands of cells that receive information about light exposure directly from the eyes and control your behavioral rhythm.  Some people with damage to the SCN sleep erratically throughout the day because they are not able to match their circadian rhythms with the light-dark cycle.  Most blind people maintain some ability to sense light and are able to modify their sleep/wake cycle.

The brain stem, at the base of the brain, communicates with the hypothalamus to control the transitions between wake and sleep.  (The brain stem includes structures called the pons, medulla, and midbrain.)  Sleep-promoting cells within the hypothalamus and the brain stem produce a brain chemical called GABA, which acts to reduce the activity of arousal centers in the hypothalamus and the brain stem.  The brain stem (especially the pons and medulla) also plays a special role in REM sleep; it sends signals to relax muscles essential for body posture and limb movements, so that we don’t act out our dreams.

The thalamus acts as a relay for information from the senses to the cerebral cortex (the covering of the brain that interprets and processes information from short- to long-term memory).  During most stages of sleep, the thalamus becomes quiet, letting you tune out the external world.   But during REM sleep, the thalamus is active, sending the cortex images, sounds, and other sensations that fill our dreams. 

The pineal gland, located within the brain’s two hemispheres, receives signals from the SCN and increases production of the hormone melatonin, which helps put you to sleep once the lights go down.  People who have lost their sight and cannot coordinate their natural wake-sleep cycle using natural light can stabilize their sleep patterns by taking small amounts of melatonin at the same time each day.  Scientists believe that peaks and valleys of melatonin over time are important for matching the body’s circadian rhythm to the external cycle of light and darkness.

The basal forebrain, near the front and bottom of the brain, also promotes sleep and wakefulness, while part of the midbrain acts as an arousal system.  Release of adenosine (a chemical by-product of cellular energy consumption) from cells in the basal forebrain and probably other regions supports your sleep drive.   Caffeine counteracts sleepiness by blocking the actions of adenosine.

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

Sleep Stages and Mechanisms

Sleep Stages

There are two basic types of sleep:  rapid eye movement (REM) sleep and non-REM sleep (which has three different stages).  Each is linked to specific brain waves and neuronal activity.  You cycle through all stages of non-REM and REM sleep several times during a typical night, with increasingly longer, deeper REM periods occurring toward morning. 


Stage 1 non-REM sleep is the changeover from wakefulness to sleep.  During this short period (lasting several minutes) of relatively light sleep, your heartbeat, breathing, and eye movements slow, and your muscles relax with occasional twitches.  Your brain waves begin to slow from their daytime wakefulness patterns.


Stage 2 non-REM sleep is a period of light sleep before you enter deeper sleep.   Your heartbeat and breathing slow, and muscles relax even further.  Your body temperature drops and eye movements stop.  Brain wave activity slows but is marked by brief bursts of electrical activity.  You spend more of your repeated sleep cycles in stage 2 sleep than in other sleep stages.


Stage 3 non-REM sleep is the period of deep sleep that you need to feel refreshed in the morning.  It occurs in longer periods during the first half of the night.  Your heartbeat and breathing slow to their lowest levels during sleep.  Your muscles are relaxed and it may be difficult to awaken you.  Brain waves become even slower.


REM sleep first occurs about 90 minutes after falling asleep.  Your eyes move rapidly from side to side behind closed eyelids.  Mixed frequency brain wave activity becomes closer to that seen in wakefulness.  Your breathing becomes faster and irregular, and your heart rate and blood pressure increase to near waking levels.   Most of your dreaming occurs during REM sleep, although some can also occur in non-REM sleep.  Your arm and leg muscles become temporarily paralyzed, which prevents you from acting out your dreams.  As you age, you sleep less of your time in REM sleep.  Memory consolidation most likely requires both non-REM and REM sleep.

Sleep Mechanisms

Two internal biological mechanisms–circadian rhythm and homeostasis–work together to regulate when you are awake and sleep.  

Circadian rhythms 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.  


Your body's biological clock is based on a 24-hour day and controls most circadian rhythms. These rhythms affect a variety of functions including body temperature (represented as the white line on the chart above). Melatonin - a hormone released by the pineal gland - helps you feel sleepy once the lights go down. The peaks and valleys of melatonin (represented as the gold line above) are important for matching the body's circadian rhythm to the external cycle of light and darkness.

Sleep-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.

Factors that influence your sleep-wake needs include medical conditions, medications, stress, sleep environment, and what you eat and drink.  Perhaps the greatest influence is the exposure to light.   Specialized cells in the retinas of your eyes process light and tell the brain whether it is day or night and can advance or delay our sleep-wake cycle.  Exposure to light can make it difficult to fall asleep and return to sleep when awakened.

Night shift workers often have trouble falling asleep when they go to bed, and also have trouble staying awake at work because their natural circadian rhythm and sleep-wake cycle is disrupted.  In the case of jet lag, circadian rhythms become out of sync with the time of day when people fly to a different time zone, creating a mismatch between their internal clock and the actual clock. 

How Much Sleep Do You Need?


Sleep needs change with age as shown on the chart above. Initially, babies sleep 16-18 hours a day. School-age children and teens need about 9.5 hours of sleep each night. Most adults require 7-9 hours of sleep at night. However, older adults (age 60 and above) tend to sleep for shorter periods at night.

Your need for sleep and your sleep patterns change as you age, but this varies significantly across individuals of the same age.   There is no magic “number of sleep hours” that works for everybody of the same age.  Babies initially sleep as much as 16 to 18 hours per day, which may boost growth and development (especially of the brain).  School-age children and teens on average need about 9.5 hours of sleep per night.  Most adults need 7-9 hours of sleep a night, but after age 60, nighttime sleep tends to be shorter, lighter, and interrupted by multiple awakenings.  Older people are also more likely to take medications that interfere with sleep. 

In general, people are getting less sleep than they need due to longer work hours and the availability of round-the-clock entertainment and other activities. 

Many people feel they can "catch up" on missed sleep during the weekend but, depending on how sleep-deprived they are, sleeping longer on the weekends may not be adequate.

Dreaming and Sleep Tracking


Everyone dreams.  You spend about 2 hours each night dreaming but may not remember most of your dreams.   Its exact purpose isn’t known, but dreaming may help you process your emotions.  Events from the day often invade your thoughts during sleep, and people suffering from stress or anxiety are more likely to have frightening dreams.  Dreams can be experienced in all stages of sleep but usually are most vivid in REM sleep.  Some people dream in color, while others only recall dreams in black and white.


Tracking Sleep Through Smart Technology

Millions of people are using smartphone apps, bedside monitors, and wearable items (including bracelets, smart watches, and headbands) to informally collect and analyze data about their sleep.  Smart technology can record sounds and movement during sleep, journal hours slept, and monitor heart beat and respiration.  Using a companion app, data from some devices can be synced to a smartphone or tablet, or uploaded to a PC.  Other apps and devices make white noise, produce light that stimulates melatonin production, and use gentle vibrations to help us sleep and wake.

The Role of Genes and Neurotransmitters

Chemical signals to sleep     

Clusters of sleep-promoting neurons in many parts of the brain become more active as we get ready for bed.  Nerve-signaling chemicals called neurotransmitters can “switch off” or dampen the activity of cells that signal arousal or relaxation.  GABA is associated with sleep, muscle relaxation, and sedation.  Norepinephrine and orexin (also called hypocretin) keep some parts of the brain active while we are awake.  Other neurotransmitters that shape sleep and wakefulness include acetylcholine, histamine, adrenaline, cortisol, and serotonin.

Genes and sleep

Genes may play a significant role in how much sleep we need.  Scientists have identified several genes involved with sleep and sleep disorders, including genes that control the excitability of neurons, and "clock" genes such as Per, tim, and Cry that influence our circadian rhythms and the timing of sleep.   Genome-wide association studies have identified sites on various chromosomes that increase our susceptibility to sleep disorders.  Also, different genes have been identified with such sleep disorders as familial advanced sleep-phase disorder, narcolepsy, and restless legs syndrome.  Some of the genes expressed in the cerebral cortex and other brain areas change their level of expression between sleep and wake.  Several genetic models–including the worm, fruit fly, and zebrafish–are helping scientists to identify molecular mechanisms and genetic variants involved in normal sleep and sleep disorders.  Additional research will provide better understand of inherited sleep patterns and risks of circadian and sleep disorders. 


Sleep studies

Your health care provider may recommend a polysomnogram or other test to diagnose a sleep disorder.  A polysomnogram typically involves spending the night at a sleep lab or sleep center.  It records your breathing, oxygen levels, eye and limb movements, heart rate, and brain waves throughout the night.   Your sleep is also video and audio recorded.  The data can help a sleep specialist determine if you are reaching and proceeding properly through the various sleep stages.  Results may be used to develop a treatment plan or determine if further tests are needed.

Tips for Getting a Good Night's Sleep


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

  • Set a schedule – go to bed and wake up at the same time each day.
  • Exercise 20 to 30 minutes a day but no later than a few hours before going to bed.
  • Avoid caffeine and nicotine late in the day and alcoholic drinks before bed.
  • Relax before bed – try a warm bath, reading, or another relaxing routine.
  • Create a room for sleep – avoid bright lights and loud sounds, keep the room at a comfortable temperature, and don’t watch TV or have a computer in your bedroom.
  • Don’t lie in bed awake.  If you can’t get to sleep, do something else, like reading or listening to music, until you feel tired.  
  • See a doctor if you have a problem sleeping or if you feel unusually tired during the day.  Most sleep disorders can be treated effectively.

Hope Through Research

Scientists continue to learn about the function and regulation of sleep.  A key focus of research is to understand the risks involved with being chronically sleep deprived and the relationship between sleep and disease.  People who are chronically sleep deprived are more likely to be overweight, have strokes and cardiovascular disease, infections, and certain types of cancer than those who get enough sleep.  Sleep disturbances are common among people with age-related neurological disorders such as Alzheimer’s disease and Parkinson’s disease.  Many mysteries remain about the association between sleep and these health problems.  Does the lack of sleep lead to certain disorders, or do certain diseases cause a lack of sleep?  These, and many other questions about sleep, represent the frontier of sleep research.

The Science of Sleep - American Chemical Society

December 2014/January 2015
By Kristin Harper

Download PDF: English | Spanish

When the Columbia, Mo., school board announced they were considering moving Rock Bridge High School’s start time from 7:50 a.m. to 7:20 a.m., it was the last straw for sophomore Jilly Dos Santos. “I thought if that happens, I will die. I will drop out of school!” she said.

Jilly set up a Facebook page and a Twitter account to encourage her fellow students to show up at the school board meeting where the vote was taking place. With their help, she made hundreds of posters and flyers. Then, armed with a mountain of scientific research she and her friends had collected, she stood before the board and made the case against an earlier start time. It worked.

The school board abandoned the idea of beginning the day at 7:20 a.m. Jilly was not through, though. The next day, she started campaigning for an even later start time, and her persistence paid off. Eventually, the board voted 6 to 1 to ring the first bell more than an hour later, at 9 a.m.

Why do teenagers find it so hard to wake up early, and why are more and more school districts opting for later high school start times? It turns out the answer can be found in the chemistry of sleep.

Our Internal Clocks

Our bodies release chemicals in a 24-hour cycle, nudging us to do certain activities at certain times. Each of these cycles is called a circadian rhythm (see “Circadian Rhythms and Life,” p. 10). One of the most important chemicals involved in this process is melatonin, a hormone that makes us feel drowsy. The amount of melatonin in our bodies starts increasing in the evening and peaks in the middle of the night, letting us know it is time to sleep. It then decreases by morning, allowing us to wake up refreshed.

Circadian Rhythms and Life

Circadian rhythms are not unique to humans—they are also found in plants, animals, fungi, and even bacteria. External signals, such as light, trigger the cyclical release of chemicals that signal when to start and stop different actions. Circadian rhythms govern all types of activities: feeding times in bees, leaf movement in plants, and DNA replication in fungus, among others. In humans, circadian rhythms are best known for governing our sleep schedules.

To maintain our 24-hour sleep schedule, our bodies translate information about time of day into melatonin production. This process starts in the eye’s retina. When the retina is exposed to light, a signal is relayed from the retina to an area of the brain, called the suprachiasmatic nucleus, which plays a role in making us feel sleepy or wide awake.  

The suprachiasmatic nucleus sends signals to other parts of the brain that control hormones and body temperature. Then, signals travel from the brain down the spinal cord and back up to the pineal gland, a small pinecone-shaped organ in the brain where melatonin production takes place. During the day, such signals prevent the pineal gland from producing melatonin. But when it is dark outside, these signals are not activated, and the pineal gland is able to produce melatonin (Fig. 1). In other words, exposure to light prevents melatonin release, which keeps us awake, and lack of exposure to light causes melatonin release, which tells us to “go to sleep!”

These brain signals explain how our bodies know when to produce melatonin, but how is melatonin synthesized? Melatonin is actually derived from an amino acid called tryptophan, which is absorbed from the bloodstream to the pineal gland. An amino acid is an organic acid used to make proteins.

The synthesis of melatonin from tryptophan occurs through a multistep process (Fig. 2). First, tryptophan is converted to another amino acid, 5-hydroxytryptophan, through the action of the enzyme tryptophan hydroxylase and then to a brain chemical called serotonin by an enzyme called aromatic amino acid decarboxylase. An enzyme is a biological catalyst that speeds up the rate of a chemical reaction.

Serotonin's conversion to melatonin involves two enzymes: serotonin-N-acetyltransferase (SNAT), which converts the serotonin to N-acetylserotonin with the addition of an acetyl group (COCH3), and hydroxyindole-O-methyltransferase (HIOMT), which transfers a methyl group (CH3) to the N-acetylserotonin. The activities of both enzymes rise soon after the onset of darkness.

The amount of melatonin produced depends on the activity of SNAT, which peaks when it is dark outside. Exposure to light induces signals that, as explained earlier, travel from the retina to the suprachiasmatic nucleus and then to the pineal gland, resulting in the degradation of SNAT. However, at night, SNAT is phosphorylated. Phosphorylation, which is simply the addition of a phosphate group (PO43−) to a protein or other organic molecule, prevents SNAT from being degraded and thus increases melatonin production.

When it is morning time, SNAT is degraded again, the amount of melatonin decreases, and you feel ready to start the day.

Teens and Melatonin

As we have learned more about the chemistry of sleep in the past few decades, we have come to realize that it really is harder for teens, such as Jilly, to wake up early. In teens, melatonin is produced about three hours later in the 24-hour sleep cycle than in children or adults. This keeps them up late, and when they wake up early, SNAT is still active and they are still producing melatonin, which leaves them feeling sleepy in the morning.

Teenagers typically require nine hours of sleep per night. But because of their late bedtimes and schools’ early start times, they average only seven hours of sleep per night. Because they haven’t slept long enough, they feel perpetually drowsy, which affects their ability to pay attention in classes and to learn.

What happens when a high school, such as Jilly’s, starts later? So far, schools have reported big gains. For example, the Minneapolis Public School District shifted its start time from 7:15 a. m. to 8:40 a.m. It found that students averaged more than five extra hours of sleep each week, and attendance and enrollment rates improved as well. Also, daytime alertness increased, and rates of depression decreased.

Even more surprising is the number of car crashes involving teenagers in Fayette County, Kentucky, decreased by almost 17% in the two years following its adoption of a later start time for school. So, it appears that taking into consideration a shift in the timing of melatonin production in teens can have all sorts of benefits.

Many teenagers are not lucky enough to attend a school with a later start time, however. In the 2011–2012 academic year, about 40% of U.S. high schools were still starting before 8 a.m. So what can you do if you are in this group? First, minimize exposure to artificial light at night. This includes light from TV, computers, and phones. By signaling to your body that it is daytime, these light sources facilitate the degradation of SNAT and interfere with the production of melatonin. This means you won’t feel drowsy, making it difficult to go to sleep at a reasonable time.

Another way to get more sleep is to avoid sleeping in too late on weekends. It may seem counterintuitive because if you are not getting enough sleep during the week, your body will urge you to stay in bed on weekend mornings to make up for your lost sleep. But the reality is that sleeping in on weekends can confuse your body’s biological clock, making it even tougher to wake up on weekdays.

A Balancing Act

Jilly was able to use her knowledge of chemistry to convince her school district to move to a later start time. The logistics of this kind of shift can be tough, though, which prevents many school districts from adopting this solution. Because most districts have a limited number of school buses to transport students, if high schools start later, elementary and middle schools may need to start earlier. Often, parents of younger kids do not like this idea. After all, most people don’t like to wake up earlier than they have to!

Also, some high school students involved in after-school activities dislike having to stay at school until dark. Clearly, balancing the biological sleep schedule of teenagers with the demands of society is difficult, but more and more districts are interested in trying to make later start times work.

This is a perfect example of how our understanding of chemistry—in this case, a three-hour shift in melatonin production in teens—can translate into a change that improves teens’ lives.

Selected references


J. Hoffman. To Keep Teenagers Alert, Schools Let them Sleep In. The New York Times, March 13, 2014: [accessed Sept 2014].


School Start Time and Sleep, National Sleep Foundation: [accessed Sept 2014].


Pannoni, A. Later High School Start Times a Challenge for Districts. US News and World Report, March 24, 2014: http://www. [accessed Sept 2014].

Kristin Harper is a science writer who lives in Seattle, Wash. Her latest ChemMatters article, “Skin Color: A Question of Chemistry,” appeared in the April/May 2014 issue.

How sleep affects health

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  • The impact of quality sleep on human health

Sleep is a physiological human need, just like hunger or thirst. If you deprive a person of sleep, then in the end he will die. In ancient times, people considered sleep to be like death - after all, when a person went to bed, closed his eyes, his breathing became less frequent and the reaction to external stimuli decreased. No wonder in ancient Greek mythology the god of sleep Hypnos and the god of death Thanatos were twin brothers. For thousands of years, people thought that the main function of sleep was rest. However, with the invention at 19In the year 28 of the electroencephalograph, a device that allows recording the electrical activity of the brain, and the discovery in 1953 of the sleep phase with rapid eye movements, scientists realized that sleep is not a monotonous state, but an active process with many functions.

We still do not know all the functions of sleep. But the forced or conscious restriction of sleep seriously affects the mental and physical health of a person. No wonder in China, sleep deprivation was considered one of the worst punishments. The Guinness Book of Records does not record experiments with conscious sleep deprivation, considering them deadly. Currently, the scientifically and documented record for the longest stay without sleep is held by Randy Gardner, who at 1963 was awake in a row, without the use of any stimulants, 260 hours and 17 minutes (11 days).

Even after one sleepless night, which happened in the life of almost every person, fatigue appears, concentration of attention decreases, difficulties arise with complex activities. If you do not sleep for 2-3 nights, then coordination of movements and focusing of vision are disturbed. In the future, irritability, slowing down of movements, slurred speech, hallucinations, and strange behavior appear. A person cannot keep up a conversation, becomes indifferent to the world around him, there are difficulties in performing the simplest household skills ... All this only confirms that quality sleep is essential for our body. nine0008

However, with the development of technology, people on our planet sleep less and less. According to the American National Sleep Foundation in 1910, the average sleep duration was 9 hours per night, in 1975 - 7.5 hours, and in 2005 - 6.8 hours per day. And the downward trend in average sleep time continues.

Sound, light (street lighting, screens of various electronic devices: phones, laptops, tablets and monitors of conventional computers) and information (primarily the Internet) "pollution" helps to reduce sleep duration. The desire to be always “online”, to follow the news in the world, significantly undermines the human psyche, because our brain is not adapted to processing such a huge amount of information, sometimes quite contradictory. nine0008

The person becomes anxious and there are difficulties with quality sleep - most often these are problems with falling asleep or frequent nighttime awakenings. A person's sleep becomes superficial and not refreshing. This, in turn, further exacerbates the lack of sleep, and eventually the same symptoms appear as in people who have not slept for two or three days in a row.

First of all, sleep is rest for the body. If sleep is not enough quantitatively or qualitatively, then the person will begin to experience physical discomfort, headaches, irritability. Moreover, most people do not even realize that the reason for their poor health is inadequate sleep. Often they say “I'm under a lot of stress right now,” “I'm busy at work,” or “I'm feeling tired.” Such people need to make up for the lack of sleep as soon as possible and restore their body. Otherwise, in the future, they will begin to make mistakes that they would never have made if their sleep was of high quality. nine0008

In the deep stages of sleep, our body produces growth hormone - somatotropin, which launches a program of complex renewal of the body and regulates metabolism. Therefore, with a lack of sleep, the risk of developing diabetes mellitus, hypertension, obesity increases, and the severity of chronic age-related diseases also increases. Not without reason, when a person is sick, he constantly wants to sleep - this is how the body “renews” itself.

Lack of sleep reduces resistance to disease. During sleep, neurotransmitters are produced - special chemicals that, like a conductor, make our body work smoothly, like a clock. Therefore, the immune system is in great need of sleep. People who sleep well get sick less. nine0008

Experienced specialists of the clinic "Family Doctor" will help you cope with any health problems. If you are not satisfied with the quality of your sleep, you snore, stop breathing during sleep (according to others) or have other complaints related to sleep or occur only at night, we recommend that you consult a neurologist - a specialist in the field of sleep disorders . To make an appointment with a neurologist, call the contact center +7 (495) 775 75 66, use the online doctor appointment service or contact the clinic reception. nine0008

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What happens to us when we fall in love?

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Image copyright Thinkstock

Image caption,

Love goes through several stages, but not necessarily in the same order

Scientists have determined what chemical processes take place in us when we are in love. The stages are always the same - but their sequence can be anything.

The word "chemistry" is figuratively used in relation to love, but in fact love is really a series of chemical reactions. Scientists believe that falling in love triggers a number of processes in our bodies that are ultimately aimed at preserving the human race. nine0008

The symptoms of love are similar to a disease state: sweaty palms, loss of appetite, euphoria, flushed face and rapid heartbeat.

Love goes through several stages - each of them depends on certain chemical elements that trigger the corresponding reactions in the body.

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Image caption,

The first stage, the desire stage, is determined by the action of sexual hormones and is expressed in the search for a partner

But the order in which the stages follow one another can be arbitrary, emphasizes a researcher at Rutgers University in New Jersey Helen Fisher. nine0008

"You may have a strong attachment to someone at work or in your social circle, and only after many months or years something happens, the situation changes, and suddenly you find yourself in love with this person," explains Helen Fisher .

"So first comes affection, then comes romantic infatuation, and only then emotions associated with sexual attraction. Or we can meet someone who seems sexually attractive to you, you fall in love with him, and only then come to a feeling of deep affection Or you can suddenly fall in love, literally lose your head because of someone with whom you had sex a long time ago, at that moment it did not cause strong feelings, "continues Fisher. nine0008

Image copyright, Thinkstock

Image caption,

The symptoms of love are disease-like: sweaty palms, loss of appetite, euphoria, a flushed face and a rapid heartbeat.

At each of these stages, different chemicals come into play, and scientists now know which elements correspond to which process.

Stage 1: Sex

Desire (or to put it more roughly, but exactly - lust) is caused in us by sex hormones testosterone and estrogen. Testosterone is not exclusively a "male" hormone. In the female body, it plays the same important role in arousing sexual desire. nine0008

Stage 2: Attraction

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Image caption

Long-term relationships are based on the instinct to care for children and secure their future apart from the object of desire, they sleep badly and are always in a state of blissful or disturbing thoughts about it. They may even lose their appetite.

At the attraction stage, a group of neurotransmitters from the monoamine group enters into action:

  • Dopamine is the same substance for which some people inject cocaine and nicotine into their bodies
  • Norepinephrine is the closest relative of adrenaline. Makes us sweat and our hearts beat faster.
  • Serotonin is the main "engine" of love, its deficiency leads to depression, and its excess leads to natural madness.

Stage 3: Attachment

These are the feelings that arise in us if the relationship is destined to last for a long time. If the attraction stage continued indefinitely, they would hardly have turned out to be anything worthwhile, except for a bunch of children. nine0008

Photo credit, Science Photo Library

Photo caption,

Oxytocin is responsible for a strong emotional bond between mother and child

Attachment is a long-term voluntary commitment, it is a bond between people who decide to form an alliance and acquire offspring.

At this stage, the nervous system releases two hormones into the body, which, according to scientists, are responsible for the social connection between people: