It is essential to listen to this language and to pay attention to these signals in order to take measures to prevent diseases. One must get warm when one feels cold, calm down when one is angry and sleep when one is tired.

Yawning is one of the body’s most significant signals. It starts in the mother’s womb and is seen throughout one’s lifetime. It stems from causes like tiredness, lack of motion, boredom, listening to monotonous talk or music, being in an oxygen poor environment, observing another yawning person, sleep deprivation, or lack of healthy sleep – in addition to pathological reasons such as epilepsy, brain infection, vascular diseases of the brain, and backside brain tumors.

While certain substances are responsible for transmitting the neural signals in the brain trigger yawning, some also act to prevent it. For instance, when endorphin levels increase, yawning decreases; but yawning increases when levels of dopamine or serotonin are elevated. Certain drugs can also lead to yawning. Continuous yawning or failing to yawn, or chronic incomplete yawning, is considered a symptom of disease.

It is well known that people who are trying to be awake are seen to yawn more than a person who is sleepy. Since the heart rate is accelerated during yawning, the amount of blood sent to the lungs and brain is improved. Because of the increased energy output, sleep is delayed, to a certain extent. The oxygen demand of the body varies throughout the day depending on the conditions. The most oxygen dependent organ is the brain. As the result of a lowered oxygen ratio in the blood, yawning occurs and the brain’s demand for oxygen is satisfied.

While sleeping, people recover from stress and anxiety. Yawning is a reminder to the body that the time for sleep has arrived. If a person cannot get enough sleep, they may struggle to focus, become nervous, or frequently yawn. Furthermore, synthetic clothing and rubber footwear are also listed among causes that lead to yawning, since these materials can cause increased levels of static electricity to accumulate in the body. The accumulated charge results in stress and exhaustion, therefore triggering yawning.

In a study, it was shown that 75% of people yawn in the morning, 50% at the end of the day, 30% after meals, and 47% while stretching. Scientists also discovered a relationship between yawning and brain temperature. Yawning was observed to stop during breathing through the nose, which cools the forehead. In this sense the brain resembles a computer; it works better when cooled. Yawning also cools the brain and therefore makes it function more efficiently. In other terms, yawning works like a fan on a computer. Exhaustion and insomnia trigger yawning because these increase brain temperature.

There are other factors that cause yawning. The over consumption of coffee and tea means more stimulants in the body. Caffeine stimulates the brain for more energy consumption. Thus, if sleep is postponed, due to the increased temperature, yawning is observed. If people grow dehydrated, they may also yawn. Therefore, experts recommend drinking water regularly. Talking on the phone for a long time tires the brain, and can cause yawning. Taking a shower with water warmer than the body temperature also leads to yawning because it stimulates an excessive secretion of hormones that cause sleepiness. Thus, it is better to take showers with very warm water in the evening and with less warm water in the morning.

Yawning becomes frequent when acidic beverages are excessively ingested, when exposed to noise for extended periods, during extreme exhaustion, or prolonged exposure to fluorescent lighting.

As in the case of acidic drinks, some individuals may display sensitivity and intolerance towards different foods. For example, celiac patients have a hard time digesting starch. They suffer from yawning, headaches, and exhaustion when they ingest starch. In young people and among individuals who consume salty foods, due to the increased accumulation of static electricity, yawning is more common. In addition, yawning also is witnessed during psychological stress. For instance, parachuters before they jump off the plane, athletes before starting a race, students before entering an exam, passengers before departure, and musicians preparing for a concert … all were observed to yawn frequently.

Hypothalamus and yawning

The hypothalamus, which forms the small portion at the front of the brain and maintains communications between the brain and the endocrine system with the pituitary gland, is assigned very important tasks, such as controlling excitement, hunger and thirst, sleep, blood pressure, and body temperature. The body responds to problems regarding these controls by yawning. For example, in cases when a high oxygen demand movement is made, the hypothalamus stimulates the lungs for more air and causes a person to yawn. From this point of view, the center responsible for yawning is believed to be located at hypothalamus.

Is yawning contagious?

Yawning is contagious, just like laughing. It is known that yawning is observed in people who witness somebody else yawning, hear somebody yawn – and even in people who think about yawning or read an article about it. A psychologist determined that yawning is contagious after making students watch people yawn, discovering that around 50% of the people who see a yawning person also yawn within a short amount of time. Experts note that the imitation of other people yawning can be an empathic reflex.

The facial expressions of yawning individuals are predicted to have an effect on other people – and that these expressions promote yawning! Mirror neurons in the brain are activated; therefore yawning takes place by feeling what the other person is experiencing.

Mirror neurons are cells that are affected by the observation of certain behaviors, especially among vertebrates watching members of their own species. It has been discovered that kids who are under the age of five are not affected by watching others yawn since their empathy and mirror neuron connections are not fully developed. The regions of the brain activated during contagious yawning and empathic behavior are the same. However, for non-contagious yawning people, these regions were found to be inactive. Therefore, yawning is more frequently observed in people who have improved emphatic skills. For instance, it has been determined that individuals suffering from heavy hearing loss do not display contagious yawning.

Do animals also yawn?

Yawning is not unique to humans; it can also be observed in some animals. When animals like lions, tigers, cats, dogs, hippopotamus, and even iguanas yawn, they open their mouths and extend their tongues, which can be frightening. Animals like horses, rabbits, penguins, and goats yawn with their eyes half closed, giving them a placid, funny look. A majority of animals yawn when they encounter a situation requiring attention, though it is also considered a possible form of communication for animals living in congregations. As in humans, it’s believed that yawning helps to regulate body temperature. The brain temperatures of yawning mice were reported to become normal.

Yawning and washing

There is a static electric balance in the human body. Maintaining this balance is necessary for our health. Yawning serves as a symptom of some psychosomatic diseases that disrupt this balance. Contact with water and soil is one way our body regulates its static electricity when warned of an imbalance through yawning. This is why washing our body with a shower or with practices like ablution refreshes the skin and nervous system by helping achieve this balance. But washing the head, hands, and feet as in ablutions, the farthest parts of the body where blood vessels branch out, is especially useful. If the water is warm, vessels expand; if the water is cold, they contract, which provides elasticity and fitness.

Further reading

1. Iacobani M. 2009. “Imitation, empathy and mirror neurons,” Annual Review Psychology.
2. Walusinski O. 2009. Yawning in diseases, European Neurology.

We tend to overlook our skin, but it performs many vital functions for our bodies – including coming to our rescue in emergencies.

Since it is designed to function within very precise limits, our body is very susceptible to small temperature changes. Since abnormalities in these changes occur, the body has various mechanisms to keep its temperature constant. One of these mechanisms works by changing the amount of blood in the veins underneath the skin. When talking about body temperature, it is important to distinguish between the internal and external body temperature. The internal temperature is the temperature of the brain and internal organs, while the external body temperature is the temperature of the skin.

Normally, arteries that transport clean blood, and veins that carry dirty blood, are not connected; therefore clean and dirty blood never mix. However, as a consequence of some illnesses or birth defects, an abnormal bridge between arteries and veins may be present. This kind of condition is usually called arteriovenous shunts, or arteriovenous fistula. In these kinds of situations, blood is pumped directly from arteries to veins. In other words, clean blood flows towards dirty blood. Normally, the clean blood has to travel the body, providing oxygen and other supplements to cells, while collecting carbon dioxide and returning to the heart to be cleaned again.

An incredible network for the transportation of substances from the blood in arteries and veins has been created. If this system, known as the “capillary network,” did not exist, none of our organs could be fed, and the circulatory system would not be able to provide its vital function.

The system is necessary for two reasons. The speed of the blood in the arteries and veins is too fast for anything to be transported to the organs, and their walls are too thick to allow transportation of substances. Therefore, the blood travels from the arteries to the capillaries, and after the trading of oxygen and other substances with carbon dioxide is completed, it flows to the veins. If any kind of abnormalities exist, the blood flows directly from the arteries to the veins, therefore skipping the capillaries. As a consequence, the organs aren’t fed and the blood gathers in the veins without fulfilling its purpose. Naturally, the oxygen and nutrition balance of the organs gets messed up. The blood is pumped out of the heart with no purpose and heart failure becomes inevitable.

The capillary network has been assigned the task of communication between arteries and veins. The skins is our only organ where the blood flows directly from arteries to veins; AV shunts accomplish a very important duty in this function.

There is a network of veins underneath the skin. The number of veins in this network is so many that if they were completely filled up, they could hold up to two liters of blood in the skin. Blood is pumped to the skin for two purposes: to provide oxygen and nutrients to the cells, and to collect carbon dioxide and waste products in the cells, as is done with every organ; and to monitor the internal temperature of the body by sending blood to the skin if the temperature gets too high, similar to what radiators in cars do when the engine gets too hot.

There is also the subcutaneous fat tissue underneath the skin which acts as an insulator. The vein network mentioned above is inside this fat tissue. There is a continuous flow of blood from the capillaries that feed the skin towards this network of veins. Moreover, especially in areas where the skin is exposed – such as the hands, feet, face and ears – there is a blood flow from the small arteries towards this network of veins. Contrary to other organs in the body, blood flows directly from the arteries to the veins. If this direct blood flow did not exist, the amount of blood in the skin’s veins would be close to zero, because the amount of blood necessary for skin nutrition is very little. However when the internal temperature rises too much, the amount of blood, which is normally close to zero, can suddenly increase to as much as 30% of the blood pumped by the heart. In this case, the body’s internal temperature is being transported to the skin. This is an incredibly efficient cooling system. However, if the weather is cold, the AV shunt veins are switched off and the skin’s blood flow is decreased until close to zero, therefore maintaining internal temperature. The fat tissue underneath the skin also has a very important function, as it acts as insulation, helping maintain temperature.

Body temperature and the body’s systems work in perfect coordination with each other. We can observe a very simplified version of this system in computer based air conditioners. However, when we reflect upon the incredibly sophisticated cooling system of the human body, we come to the conclusion that no other system is as perfect as that.

The hypothalamus, which has various vital duties for the brain, was also given the very important mission of controlling the body’s temperature. There are hot and cold heat receptors in various parts of the hypothalamus. When body temperature increases, these receptors are activated. As a consequence of this warning, skin veins all over the body expand. Simultaneous with the expansion of the veins, sweat is excreted.

The hypothalamus also has the duty of suppressing the mechanisms that produce heat throughout the body. For example, trembling is stopped and general metabolism is slowed down to decrease body temperature. As metabolism slows down, the production of heat becomes minimal, and cooling takes place. In conditions where the body temperature is too cold, some hormones secreted in the hypothalamus trigger the pituitary, and then the thyroid, hormones. Since thyroid hormones are responsible for increasing metabolism, body temperature increases. However if body temperature increases above normal, the control of the hypothalamus on the thyroid is reversed, and thyroid hormones are decreased, therefore decreasing body temperature.

There is one more reason for placing so many veins in the perfect and miraculous body’s skin: except for extremely cold weather conditions, quite a large amount of blood exists in these veins that are not used for nutritional purposes. Some of our organs act as storage for blood; two of the most important ones are the spleen and liver. Another one is the skin. In the course of losing blood, or an illness that increases the need for blood, the spleen and liver shrink. As a consequence of this shrinkage, the blood inside them is sent to the heart, through veins, and distributed to the areas in need of blood. This increases the heart rate.

A similar scenario occurs in the skin. The veins responsible for cooling shrink, and the blood they contain is sent to the heart with the help of the main veins, therefore helping the heart pump. During heavy loss of blood, the blood in the skin comes to the rescue. Patients who are losing blood have incredibly cold and pale skin. This is because the blood in the skin has reduced to a minimum.

The obverse of this happens in an illness called erythromelalgia, where more blood than normal flows from the arteries to the veins in the skin. This is mostly seen in the hands, feet, nose, and ears, since AV shunts are more prevalent in these areas of the skin. The symptom of this illness is burning pain, which is triggered by heat and soothed by cool temperatures. The nutrition of the skin decreases and some substances produced because of the absence of oxygen increases redness, heat, and pain, since some of the capillaries feeding the skin shut down and all of the blood flows from arteries to veins with the AV shunts.

Our skin protects our muscles and bones, and contributes to the beautiful aesthetic of our body. It provides our sense of touch, and is therefore a means for us to experience the material world, as well as providing temperature control for our bodies. It can clearly be seen that the relationship between the skin and the veins could not have evolved by the consequence of coincidence.