Blood pressure is the force with which the liquid - or blood - presses against the walls of the vessel. There are systolic and diastolic pressure. What's the difference between them? Systolic blood pressure is measured during systole of the left ventricle, and diastolic pressure - just before the ejection of blood from the heart. What exactly is blood pressure, what factors influence it? What is the normal blood pressure and what are the standards for systolic and diastolic blood pressure?

Pressure - blood pressure characteristics

Arterial pressureis the force with which the fluid presses against the vessel walls. It is worth knowing what it is and what influences it, and thus understand what is hypertension and how we can deal with it. To understand exactly what pressure is and what affects it, it is essential to review some aspects of the anatomy of the circulatory system.

The arteries in our body are structured differently depending on their size - large vessels, such as the aorta, contain a lot of elastic connective tissue, which makes them quite flexible. The influence of the nervous or endocrine systems on the diameter of these vessels is small.

Smaller arteries, in turn, contain a lot of smooth muscles and nerve endings of the autonomic nervous system, the contraction and relaxation of muscle fibers causes changes in the diameter of the vessels, and with their large number in the body, this has a large impact on pressure. By widening and narrowing these arteries, the amount of blood flowing to all organs in the body can be regulated according to their current needs. The autonomic nervous system affects blood pressure in two ways - the parasympathetic part causes it to decrease and the sympathetic part causes it to increase.

Blood pressure - what is it?

The contraction of the heart pushes a certain amount of blood into the aorta and slightly stretches the aortic wall. An increase in blood volume and a relatively small change in vessel size increase the pressure. It propagates further along the arteries, following the law of communicating vessels, creating a so-called pressure wave.

Stretching the aortic wall allows for storageenergy from the activity of the heart, which is released as part of the artery returns to its previous size. Also, this change in shape is transmitted circumferentially along the course of the vessel, which ensures that the wall continues to act on the blood inside, i.e. air effect. Such changes in the diameter of the arteries ensure that blood is continuously pushed around the periphery, even during the diastole of the heart, maintaining its flow and positive blood pressure values.

The pressure wave and vessel deformation is the pulse wave and it corresponds to the systolic pressure. This is what we feel when we measure our pulse. The speed of the pulse wave propagation depends on the elasticity of the vessels, so that in harder vessels it propagates faster.

Hardening of the arteries progresses with age, and therefore blood pressure increases slightly with age, but the process is very slow and blood pressure norms do not change over the years. The hardening of the walls significantly accelerates atherosclerosis, therefore it is important in the development of hypertension. The diameter of hardened vessels is much more difficult to regulate the nervous or endocrine systems.

Pressure as a physical quantity depends on the flow rate and resistance of blood vessels, resistance in turn depends on the difference in pressure and the amount of blood ejected from the heart (this amount of blood is the cardiac output), the greatest resistance is noted in small arterioles, because they have the smallest light and, moreover, the possibility of its adjustment. The flow rate is the amount of blood that flows in and out of the arteries. The flow is of course consistent with the pressure difference - from more to less, and is pulsating - in line with the heartbeat.

Systolic and diastolic blood pressure - what is it?

Blood pressure is always described with two values ​​ and:

  • systolic pressure- this is the highest pressure in the circulatory system. It is measured during the contraction of the left ventricle - the maximum ejection of blood
  • diastolic pressure- is recorded just before the ejection of blood from the heart and is the lowest pressure that can be recorded in the arteries. The reason it does not drop to zero during diastole is because the walls of the arteries give up their stored energy and put pressure on the blood inside
Important

Systolic and diastolic pressure - norms

Under normal conditions, the measured blood pressure values ​​are respectively 120 and 80mmHg, which we write 120/80, the difference between them is the pulse pressure and amounts to about 40mmHg, the mean arterial pressure is calculated by adding the diastolic to 1/3 of the difference between the systolic anddiastolic.

Pressure - which affects the correct pressure

Neither low blood pressure nor high blood pressure are beneficial to he alth. There are many factors that influence the amount of pressure. It depends especially on the aforementioned: cardiac output and vascular resistance, which is why they are greatly influenced by the amount of circulating blood and the efficiency of the heart - the strength with which it works, the regularity of the rhythm, the structure of the valves, especially the aortic ones.

1. Nervous system

The influence of the nervous system on blood pressure is also large by influencing the strength of heart contractions and vascular resistance - hence it changes under the influence of emotions, to such an extent that in some patients the white coat effect is observed, i.e. an increase in blood pressure at the time of measurement by a doctor. For this reason, among others, home measurements are very important in people suffering from arterial hypertension. The influence of the nervous system is also visible at night, when the parasympathetic nervous system dominates and the pressure drops by up to 20mmHg. Mental condition and coping with stress and difficult situations are equally important. Frequent nervousness causes an increase in the nervous system tension, activation of its sympathetic part and an increase in pressure.

2. Endocrine system

Vascular resistance, and thus indirectly blood pressure, is also regulated by the endocrine system - e.g. thyroid, adrenal glands, parathyroid gland, pituitary gland. The hormones of these glands cause an increase in blood pressure, especially adrenaline, and e.g. prostaglandin E - its decrease. The influence of the nervous and endocrine systems is clearly visible in the case of pain. This feeling causes an increase in pressure, among other things, by an increase in the secretion of adrenaline and the tone of the sympathetic nervous system. Another factor is exercise, but its effects can be twofold. Static sports, i.e. lifting weights, cause temporary increases in blood pressure, but also increase blood pressure for a long time, which is one of the reasons why they are not he althy for the cardiovascular system. Dynamic sports, such as running, cycling, swimming, if practiced regularly, reduce blood pressure and have a beneficial effect on he alth.

3. Bad diet, obesity, smoking

Diet also affects blood pressure - especially s alt, alcohol. They change the amount of circulating blood and the work of smooth muscles in the walls of the vessels. Another factor is obesity, which increases blood pressure because the fatty tissue has a lot of resistance. Smoking, on the other hand, promotes the stiffness of the artery walls and causes the secretion of small amounts of adrenaline.

The above-mentioned factors are the most important, but the multitude of reasons for the pressure change makes it impossible to list them all. Most of them work through the nervous system. Coffee or tea drunk regularly has little effect on blood pressure, as does atmospheric pressure - its changes may make you feel worse, but in a different mechanism than changes in blood pressure.

Changes in blood pressure are also recorded during the change of position, due to the force of gravity. When standing or sitting, the blood drops towards the feet and changes are noticeable depending on the height of the body. For this reason, immediately after changing position, the heart speeds up a little, in order to ensure the blood supply to places where there is less of it.

Therefore, blood pressure measurement should be taken after a short period of rest, and the cuff of the blood pressure monitor is placed over the arm at the same level as the heart, using appropriate equipment that ensures reliable, repeatable measurements.

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What is venous pressure?

Venous pressureis a much less frequently measured parameter, its evaluation requires the insertion of a catheter in the area of ​​the right atrium, and therefore it is an invasive test. The venous pressure is much lower than the arterial pressure, it is about 15-20 mmHg and it can drop to 0 at times, because the veins are very flaccid and do not have their own pump. Venous pressure is most often measured in critically ill patients with shock. It allows the assessment and planning of IV fluid administration as it best represents the patient's hydration status.

Category:

Cardiology