When we have been sitting or lying for a long time we can suffer from orthostatic hypotension due to an insufficient operation of the sympathetic nerves.

When we are lying down, the blood pressure in our arteries is pretty much equal throughout the body. When we stand up, the blood pressure is affected by the gravity and increases in the vessels under the heart, while decreasing in the brain. If we lie down again, the blood pressure in the arteries balances once again. If these changes cannot be naturally controlled, then we may suffer an increase or decrease in blood pressure, which could result in a fatal injury.

There are baroreceptors in the walls of main arteries whose tasks are to measure constantly the blood pressure and to send data (electrical signals) to the brain, informing it about the blood pressure in the body. These baroreceptors are located in the aorta as it leaves the heart and in the carotid artery as it enters the brain. With the onset of hypertension, the frequency of the signals that are sent to the brain increases and this drops in case of hypotension. The center of vessel movement in the brain, with regard to the frequency of electrical signals it receives, perceives a low or high blood pressure.

In the brain is a vasomotor center; this continuously controls the blood pressure and regulates it. This center constantly receives data about blood pressure. If the pressure decreases, the signals of the sympathetic nerve increase. If the pressure increases, the signals to the parasympathetic nerves are suppressed. As a result of sympathetic irritability, the heart begins to beat faster and stronger. It pumps much more blood in a unit of time, and thus the blood pressure increases. The arteries and veins also constrict and owing to this constriction in the arteries, the blood pressure increases further. As a consequence of constriction in the veins, the extra blood that is stored inside the veins is pumped into the heart. Now, as the heart is receiving greater volumes of blood, it works faster and contributes to the increase in the pressure. In the meantime, as a result of the suppression of parasympathetic nerve signals, the heart contracts faster and stronger, thus pumping much more blood.

As the blood pressure rises, the mechanism which is in charge of reducing the pressure via vasomotor center is triggered. While pressure is applied to the sympathetic nerves, the signals that are being sent to the heart and vessels decrease. Thus, the rate of systole and the amount of blood which is being pumped decreases. As the arteries receive less blood the volume of blood in the system falls off and as the arteries and veins expand, the blood pressure falls. Due to the dilatation in the veins, the volume of blood which is sent to the heart also decreases and as a result the heart pumps less blood and the blood pressure drops.

However, by triggering the parasympathetic nerves, the signals that are sent to the heart increase. This helps to slow the heart down and ensures that there is less blood pumping through the system. As a result, the blood pressure which has been reduced via the sympathetic system is reduced even further with the parasympathetic system. At this point, it is necessary for there to be a rapid drop in blood pressure, which is provided by the simultaneous functioning of different mechanisms.

We cannot control this system and it acts extremely rapidly and with great elegance. Even in the systole period, when the heart is pumping the blood and there is a short and sudden increase in pressure and in the diastole period, when the heart relaxes and there is a short and sudden decrease in pressure, the system is in charge and functioning at every second, operating to increase the hypotension and to decrease the hypertension. The average healthy human heart beats 70 times per minute. Consequently, there are 70 systole and 70 diastole stages every minute; thus a normal balance can be maintained by decreasing the pressure, which increases 70 times every minute, and by increasing the pressure, which decreases 70 times every minute; this is how the body maintains a normal balance. In other words, this system functions 140 times every minute. Is it possible that this system, which operates throughout our life, a system that we are not aware of, a system that is so sensitive and vital to our lives, a system the details of which have only recently been understood after centuries of observation could be nothing more than a coincidence?

The pressure regulating system mentioned above carries out other important tasks while we are sitting and standing as well. The amount of blood going to the brain is related to the maintenance of a difference in blood pressure between the arteries and veins and to the recirculation of blood. In connection with hypotension, the pressure in the veins to the brain decreases, in order to partially compensate for the decrease in the arteries. By preventing a decrease in the difference of pressure (perfusion pressure) between the two systems, the continuity of blood going to the brain can be maintained.

In addition, a small decrease in the blood going to the brain can lead to an increase in acidity and carbondioxide in the brain tissues and to a decrease in oxygen; this results in the dilatation of the blood vessels in the brain. When these systems go into action anyone who is not suffering from orthostatic hypotension will have a stable amount of oxygen consumption in the brain when they stand up, and thus not experience dizziness.

In fact, scenes from karate movies are wonderful displays of the perfect functioning of this system. In such scenes, the fighter will jump up, and then suddenly fall to the ground; he will then suddenly spring up and performs different moves. Certainly with every movement, the blood pressure changes suddenly, but as a sign of the Creator’s mercy and grace, the body is able to maintain a balance. Should not the person watching these scenes stand in amazement, thinking: “Oh my God, what an incredible order! How great is Your knowledge, power, wisdom and art!”

As mentioned at the beginning of the article with reference to an actual sad incident, when a person whose sympathetic system is not functioning normally suddenly stands up, they can suffer from dizziness and perhaps even faint due to irregular blood pressure.

For patients suffering from orthostatic hypotension patients, it is important that they do not stand up rapidly. In addition, exercises that encourage the use of leg muscles before standing up will help pump blood towards the brain.

Pause for a minute… What would happen if this miraculous system did not exist? Consider how much time it would take you to merely get out of bed every day!

In a healthy body, all of the involuntarily functioning mechanisms seem to know what to do, at the right time and in the right amount. But are these systems really “autonomous,” doing what they will? Can it be coincidence that each time the perfect choice out of thousands of possibilities is made?

Regular controlling mechanisms are needed for our bodily activities to function properly. This duty has been given to the nervous system. The autonomic nervous system (ANS), which is in charge of controlling the vital functions of the body, is designed to function in an involuntary, reflexive manner. The operating systems of several machines that make our life easier are developed by being modeled on the ANS. Take an air-conditioned car with a thermostat for example. When the air is cold, a heat sensitive mechanism automatically starts and it provides the engine with more gas and it produces more energy. And when it is warm enough inside the car, this time the thermometer urges the system to reduce the gas-flow back to normal. Likewise, sympathetic and parasympathetic nerves placed in the autonomic system are given the duty of a regulator that restores the altered functioning of organs back to normal so that they do not upset the balance of our body.

If the light coming to our eyes is too bright, vision is blurred. When the retina is exposed to excessive stimuli this causes the parasympathetic nerves to send signals to the eyes to contract the pupils so that the sensitive layers of the eyes are protected and the vision is cleared. In darkness or under dim light, the sympathetic system is called to duty again and this time the pupils are enlarged. The sympathetic-parasympathetic (autonomic) nervous systems granted to human beings play a role in optimizing eyesight under differing intensities of light.

Parasympathetic nerves are created in a way to stimulate the saliva and tear glands, as well as the glands in organs like the nose, stomach, intestines, pancreas, etc. When the secretion in these glands is surplus to our requirements, the canals in connection with them are shrunk and the secretion is lessened. Without such a system, germs would boom, morsels would not soften in our mouth, food intake would not decompose in our stomachs, the gastric mucus which protects the inner stomach from acid would not be secreted, and the final stage of digestion, absorption of digested nutrition, would not happen. Likewise, if our tear glands did not function, sores would emerge on our eyes; if there were no nasal mucus, dust and germs suspending in the air would easily reach our lungs.

The physiological functioning of the lungs and their protection are also maintained through the sympathetic and parasympathetic systems. When our tissues need more oxygen, the sympathetic system is activated. The air sacs are enlarged and more air is let in. If toxic gases, dust, cigarette smoke or other harmful elements enter the respiratory tract or the lungs are exposed to any destructive matter, the air sacs are narrowed by the immediate intervention of the parasympathetic system. In this way, the secretion in the air sacs increases and the harmful substance is prevented from going deeper into the lungs. Then the harmful substance is thrown out through secretion and the reflex of coughing.

When the blood pressure drops below 50mm Hg for any reason (due to hemorrhage, medication, body position, etc), the sympathetic system immediately works to send blood to the brain and the heart. As these are the most vital organs, they are given priority at receiving blood. Our blood circulation is carried out within a closed-circuit system and there is a constant amount of blood. Therefore, sending an organ more blood means lessening the blood sent to other organs. To maintain this, the sympathetic system again works to cause narrowing. When food intake reaches the stomach, the parasympathetic system is stimulated to enlarge the relative veins. More blood is pumped to the stomach.

Everything in both systems is designed to protect the organs, tissues, and systems; in other words, the entire body. When a person’s blood pressure goes up, the baro-receptors, which help regulate the pressure in the veins, are stimulated in order to ward off the danger and the narrowing effect of the sympathetic system on the veins is taken under control. In this way, the pressure applied by the blood to the walls of the veins is eliminated. During physical exercise or in a state of stress, anxiety, or worry, the tissues use more oxygen and the sympathetic alarm is switched on.

Blood is pumped faster to meet the need of the tissues. During sleep, the body needs less energy and the metabolism is slow. Therefore, a slower heartbeat is required. During a time of distress or fear, the sympathetic stimulators are under pressure due to hyperventilation. Then the parasympathetic system is put into service and the heartbeat and the blood flow to tissues slow down.

Sphincters are ring shaped muscles that maintain the constriction of a body passage or orifice. With sympathetic signals they constrict and block the passage, and the parasympathetic signals ease them to open the way. If it weren’t for the sympathetic system, the urine produced in the kidneys would not be under control and we would wet our trousers. However, what happens in practice is that when the kidneys produce a certain amount of urine, two sphincters controlled by the sympathetic system contract and they prevent an untimely emptying of the bladder.

Similarly, there are sphincters in the gastro-intestinal tract. If the sympathetic system had not been given the duty of controlling them, the food we eat would not stay with us until it was absorbed and it would be disposed of immediately. On the other hand, the malfunctioning of the parasympathetic system would cause obstructions and we would suffer greatly. Take the parasympathetic system working in our urinary tract for instance. It works without our control and if it did not work, the urine collected in the bladder would press back on the kidneys and cripple them.

In some functions, like the breaking down of fats, ejaculation, increase in brain activity, or the contraction of skeletal muscles, the parasympathetic system is not involved. Since its involvement might harm the body, it is not given a duty here, and the sympathetic system on its own suffices.

There are several other functions carried out by the autonomous nervous system. It works without our will or conscious control. As humans we tend to claim: “I did this, I did that.” When you eat something, your conscious control is limited to chewing the food and swallowing it. We cannot tell our stomach to digest or not to digest the food. In a healthy body, all of the involuntarily functioning mechanisms seem to know what to do, at the right time and in the right amount. But are these systems really “autonomous,” doing what they will? Can it be coincidence that each time the perfect choice out of thousands of possibilities is made? Is it at all possible for these fascinating systems to be a just a work of random causes?