Independent work on the topic “Circulatory Organs” (grade 8)

What effect does alcohol have?

Many people believe that drinking alcohol helps lower blood pressure. However, here it is necessary to remember that we are talking about vasodilation, which does not necessarily play a positive role. Alcohol should be consumed in moderation.

Regular drinking of alcoholic beverages, even in small quantities, can increase blood pressure. You should also remember about the biologically active substances contained in many alcoholic beverages. Energy drinks pose a high risk to the human body. Combining them with alcohol can lead to the most harmful consequences.

Prevention of a sharp decrease in blood pressure

Avoid situations that provoke a decrease in blood pressure (do not get out of bed abruptly, try to avoid stuffy and hot rooms, as well as stress).

Drinking cold water quickly can also prevent orthostatic hypotension (fainting when suddenly changing body position).

Simple exercises such as crossing your legs or clenching your hand into a fist can help quickly and effectively increase blood pressure and prevent fainting.

Tilt training - regular training that simulates getting up from a lying position in young people with recurrent fainting can significantly reduce the incidence of hypotensive conditions.

What is the prevention of high blood pressure?

People who experience high blood pressure need to remember the need for regular checks. Often a person does not feel symptoms and does not suspect what danger blood pressure hides. Even with long-term hypertension, people ignore the condition, attributing everything to fatigue or overwork. It is important to understand that pressure increases when blood vessels narrow, when the heart has to work at “high speed.”

Foods containing large amounts of saturated fatty acids can lead to hypertension. The highest content of these substances is found in butter, cheeses, and sour cream. It is recommended to avoid products containing large amounts of palm oil. Cake, chocolate, cookies, fatty sausage, chips are all sources of saturated fatty acids. Of course, it is important to take into account physical activity; you need to eat exactly as much as the body needs to ensure normal functioning. Moreover, you need to take into account the composition of the products. Many manufacturers even indicate the percentage of EFA content per 100 grams.

The amount of salt consumed also needs to be reduced. Scientists have long noticed the effect it can have on the human body when consumed excessively. The biggest problem is that most foods sold on supermarket shelves contain quite a bit of salt. By using this additive in our diet, we expose our body to even more danger. For those who love salty foods, the best option to get rid of excess is physical activity. Salt can reduce the elasticity of blood vessels and negatively affect the kidneys and liver.

Concept of pressure, resistance and heart rate

Take a rubber bulb in your palm and fill it with water. Now squeeze it as hard as you can, trying not to leave a single drop inside. The water will pour out of the outlet, and the larger it is, the less effort you need to make. And vice versa. The narrower the hole, the more difficult it is to squeeze everything out of the pear cavity without leaving a trace. Now we’ll do the same thing, but let’s try to put two rubber bulbs together. Let's fill them with the same volume of water, but in one we will make a large hole for exit, and in the other - a small one. From the first, when compressed, water will pour out easily, with a slight squeeze, but to empty the second, much more force will be required. This is what happens with the heart. With one important exception: there is no one to squeeze him, and his own muscular system does all the work.

Contracting, or “contracting,” in the systole phase, it pushes out of its ventricles all the blood coming from the atria, and in the diastole phase

– rests, gaining strength for the next contraction, which will follow in a split second.

The force with which the heart muscle compresses this volume of blood in the cavity of the ventricles creates pressure, as a result of which the blood is thrown into the great vessels. But the speed with which it leaves the ventricles will depend not only on the force of compression, but also on how difficult or easy it is for it to leave the ventricle and enter the lumen of the vessel. That is, if we return to our two rubber bulbs: it will go through the larger hole, or through the smaller one. In other words, what is also important is what kind of resistance will be provided to this release from the side, so to speak, that receives it, i.e. vascular bed. Here we have come to understand several main laws that govern both the movement of blood in the heart and its movement in the body, i.e. to what forces and along what currents our kayak moved.

So, a few new concepts: blood volume, pressure and resistance to blood flow.

The simplest and long-known most important parameter that can be measured and expressed in numbers is pressure. But what is pressure? Believe me, if you want to understand what’s wrong with your child, you need to know this clearly. Only then will you be able to understand what the doctors will tell you. It's actually very simple.

Blood pressure is a number that speaks about two important aspects of blood movement: its volume and resistance to its flow in each individual period of time. It can be measured in any vessel, in any chamber of the heart. And it gives a fairly accurate idea of ​​what is happening there, inside the chamber, at each phase of the cardiac cycle.

For now we are only talking about the work of a healthy heart. And it is clear that the greater the volume of blood in the ventricle, the greater the effort required to eject it, i.e. put him under more pressure. And - the greater the resistance to ejection, the greater the effort (pressure) needed to empty the ventricle, preparing it for a new portion of blood.

The vascular bed resists blood flow as a whole, from the beginning, i.e. from the ascending aorta, to the smallest arteries and capillaries - in the large circle, and the pulmonary arteries, arterioles and capillaries - in the small circle. Consequently, the powerful left arterial ventricle works against the resistance of the gigantic vascular bed of the entire body. The right ventricle, venous, thinner-walled, works against the same gigantic volume, but much more elastic, short and “soft” vascular bed of the lungs. Accordingly, the pressure figures in the cavities of the ventricles are different, and in the vessels extending from them. These figures are reflected in Table No. 1, and you can see that the pressure under normal conditions in the right ventricle and pulmonary artery is approximately one third of the pressure in the left ventricle and vessels of the systemic circle. Remember that quantity, i.e. The volume of blood ejected from each ventricle with each contraction is normally the same. So far we have only talked about the compression of blood volume under pressure. This is the so-called systolic pressure, or the maximum pressure created in the system at the moment of contraction.

But there is a second number - this is the blood pressure in the vessels during diastole, or a relaxed and filling heart. In this phase, the valves of the aorta and pulmonary artery are closed and, with their integrity, the blood in the vessels is under pressure from the closed system of the vascular bed of the body (in the large circle) and the lungs (in the small circle). Therefore, there are two numbers of pressure - the so-called “upper” (systolic) and “lower” (diastolic) pressure.

Average numbers of normal pressure in the cavities of the heart and large vessels (mm Hg)

Please note that in newborns the pressure in the right ventricle and pulmonary artery is significantly higher than in children even in the first month of life. This is explained by the fact that the vessels and all 700 million alveoli of the lungs open gradually and are fully ready to receive the entire volume of blood from the right ventricle only a few weeks after birth.

Now let's try to answer the question - what moves the heart, what causes its rhythmic contractions. Believe me, this is also very important.

The rhythmic, sequential, regular cycle of contraction and relaxation of the heart is controlled by electrical impulses. These impulses arise in special cells of the heart muscle, the so-called cells of the conduction system. Foci of large accumulations of these cells are called “nodes”, and their branches running along the muscle fibers are called “conducting paths”. There are two nodes of the conduction system: sinus and atrioventricular, and there are several pathways. The peculiarity of the cells themselves that conduct electrical impulses is that they are capable of being excited and transmitting this excitation much faster than neighboring cells of the working, contracting myocardium, or cardiac muscle. Therefore, they are guides, showing the way to others, understanding faster than others where to go. In a normal heart, the superior sinus node is excited first. The impulse is transmitted along the conductive pathways of the walls of the atria to the lower, atrioventricular node, and then, through thinner pathways, it enters the ventricles, causing their contraction in response - the systole phase. This is followed by a pause period - diastole - and the myocardium prepares to receive a new impulse. The frequency of such impulses is the frequency of the heartbeat and pulse. In newborns - 110-120 beats per minute, in adults much less often - 65-75 beats per minute. These electrical impulses are easily recorded by fairly simple instruments. The recording of the devices is called an electrocardiogram.

We are far from thinking of teaching you how to read it: this is a matter for professionals. We just want to explain what it is and why it is done. An electrocardiogram makes it possible not only to identify disturbances in the normal conduction of impulses, but also to determine which parts of the heart are abnormally enlarged, which are constantly working with increased load, and how they cope with it. If a heart defect is suspected, your child will have this test done many times. It is painless and very informative.

We can only marvel at the incredible perfection of the cardiovascular system, which, despite all its complexity, is surprisingly simple, logical and harmonious. However, it must be absolutely accurately and correctly created. Even small changes in its structure are enough to disrupt this constant, calm and synchronous work.

Quoted from the book by G. E. Falkovsky, S. M. Krupyanko. The heart of a child. A book for parents about congenital heart defects

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Lethal pressure: indicator (how much?)

If the upper blood pressure reading reaches 300 mm Hg, this value is considered fatal.
Irreversible destructive processes begin in the body. Despite such high pressure, the level of blood supply to the organs becomes very low, and hypoxia develops. The brain, which has a unique circulatory system unlike other organs, is especially sensitive to a lack of oxygen.

The vascular ring located in the brain can function normally only with SBP values ​​in the range of 80-180 mmHg.

At high levels, autoregulation of its tone is disrupted, gas exchange is disrupted, and vascular permeability jumps sharply upward. Acute hypoxia appears, followed by ischemia. If the pressure is not reduced at this moment, a fatal ischemic stroke occurs.

• How to calculate and measure mean arterial pressure?

For the brain, the SBP level exceeds 180 mm Hg. is very dangerous.