Blood pressure - a pressure that the blood exerts on the walls of arteries. The terms "blood pressure," and "blood pressure" is often used synonymously. Blood pressure is measured more often, the concept of a single blood pressure are also capillary, venous and intracardiac pressure.
One of the fundamental principles of physics is that any liquid contained in the vessel, exerting pressure on the wall of the vessel. This is called hydrostatic pressure. Blood is not - an exception to this principle, so blood pressure is also a hydrostatic.
When the left ventricle ejects blood into the aorta, the pressure rises in the arteries. The maximum pressure in the arteries is called systolic pressure.
Further, the left ventricle relaxes and begins to fill again, and pressure drops. The minimum rate of blood pressure during relaxation of the heart muscle is called the diastolic pressure. When measuring blood pressure using a sphygmomanometer highest number in his testimony - a systolic pressure less - diastolic. Normal systolic pressure - 120 mmHg or less, diastolic pressure - mm Hg or less.
The difference between systolic and diastolic pressures is an indication of the pulse pressure, which normally varies between 40 and 50 mm Hg. Mean arterial pressure - is the average pressure of the cardiac cycle.
A sphygmomanometer measures pressure in the brachial artery, where it is slightly different from the pressure in the aorta and other large arteries. As the displacement of the aortic systolic blood pressure increases, reduced diastolic and the blood pressure as a whole is somewhat higher than in the aorta. This is because the blood is moving under the influence of the pressure gradient which gradually weakened so that the lowest pressure in the veins, capillaries, venules and arterioles.
Factors that regulate blood pressure
Mean arterial pressure is regulated by changes in cardiac output and systemic vascular resistance.
- Cardiac output - is the amount of blood that the heart emits per unit of time. This rate depends on stroke volume and heart rate. Stroke volume, in turn, is determined by left ventricular contractility (inotropy) and ventricular preload. Ventricular preload depends on the elasticity of the veins and blood volume. When reducing the elasticity of veins, which occurs, for example, when the constriction is increased central venous pressure and, as a consequence, the ventricle preload.
- The total volume of blood is regulated by renal function. Blood volume can be changed for various reasons, such as changes in body position. A great influence on heart rate, intropiyu elasticity vein, renal function and as a result, blood pressure, have a neurohumoral mechanisms.
- Systemic vascular resistance usually changes only slightly, but it may affect some pathological conditions - for example, thrombosis
Thrombosis - the cause of heart attack and stroke
When the vessels may be severely damaged. Furthermore, hypertension is sometimes observed reduction in the number of small blood vessels, which can significantly alter blood pressure.
Changes in the vascular lumen also denied a huge impact on blood pressure. In chronic hypertension because of the seal of the vessel walls, this figure could be significantly reduced.
Neurohumoral mechanisms also alter blood pressure, especially in certain forms of secondary hypertension. Often therapy aimed at lowering blood pressure, involves the suppression of humoral mechanisms.
Thereby forming blood pressure
Blood pressure is generated by the action of systole (contraction) of the ventricles in the period of exile from their blood, when each ventricle and artery corresponding circulation becomes a single camera and compression of blood ventricular wall extends to the blood in the arteries, and cast out into the arteries serving the blood acquires a certain the energy of motion. This energy is the greater, the greater the stroke volume and the higher rate of expulsion, which depends on the capacity of ventricular contraction. Jerky flow of blood from the ventricles causes an expansion of the walls of the aorta (left) and pulmonary artery (right). The spread of this wave - the cause of the heart rate.
Another cause of the blood pressure is the resistance of the walls of blood vessels. This resistance is the larger, the smaller the lumen of the blood vessel and it is formed on the periphery, in small arteries, which are called resistance arteries. The higher peripheral resistance is, the greater part of the energy converted in cardiac output increase systolic blood pressure.
Systolic, diastolic and pulse pressure
The highest level of blood pressure that occurs at the time of systole is called systolic blood pressure or maximum. Diastolic pressure - the lowest blood pressure, which occurs at the time of diastole. At this point, the blood pressure has a minimum value, which depends mainly on the peripheral vascular resistance to blood flow and heart rate. Diastolic pressure is generated due to the elasticity of the walls of arterial trunks and large branches, forming a total tensile arterial chamber - systole energy accumulates in these cells, and gradually decreasing by the end of diastole. In a normal systolic blood pressure is 100-140 mm Hg, and diastolic - 60-90 mm Hg.
The difference between systolic and diastolic pressures is called pulse pressure or pulse difference. Pulse pressure is proportional to the amount of blood ejected by the heart at each systole.
- The regulation of blood pressure in the body
Stability in blood pressure in the body provides the functionality of systems that support optimal for metabolism
Metabolism: The basis of life of all living things
blood pressure. The main activity in the functional systems is the principle of self-regulation, whereby in a healthy organism, any occasional fluctuations in blood pressure caused by the influence of various factors on the body over time and stop blood pressure returns to normal. To implement such a regulation in the body exist as pressor (increased blood pressure) factors and depressor (blood pressure lowering). By pressor include, for example, adrenaline, noradrenaline, angiotensin II, a depressor - histamine, acetylcholine.
- Methods for measuring blood pressure
The most common measurement of blood pressure in the systemic circulation, for this there are special devices (blood pressure). In the specialized departments of hospitals for diagnostic purposes often measure blood pressure in the aorta, pulmonary artery, sometimes in the arteries of the liver.
Fluctuations in blood pressure
How to beat stress? Create an oasis
causes an increase in blood pressure (BP). Stress combined with prolonged sedentary lifestyle can cause a persistent increase in blood pressure. When the muscle increases the blood pressure, with systolic pressure may exceed the initial level in 1, 5-2 times. After the cessation of exercise blood pressure temporarily falls below the baseline. Sports training with a standard load often reduces blood pressure.
With age, a person increases both systolic and diastolic blood pressure. In healthy adults, blood pressure undergoes daily fluctuations of plus or minus 10 mm Hg. In patients with increased excitability of the nervous system, these fluctuations may be more significant. Blood pressure slightly lower in women than in men.
In the development of the child's body there is a smooth increase in blood pressure, but at the age of 8-9 years, children may experience a temporary increase in blood pressure about 10 mm Hg above the age norm. The girls at puberty
Puberty child - stages of a complex path
There may be a sharp rise in blood pressure. Higher than normal levels of age with BP peculiar teenagers and young men of high growth, as well as those who started early puberty.
Increased blood pressure compared with the optimum values for the body called arterial hypertension, the reduction - hypotension.