Blood pressure
Blood moves through the circulatory system due to the pressure difference between aorta and the mouth of the hollow veins. Reducing the differential pressure slows the blood flow and the fall of this difference to zero completely stops blood flow.
Also the heart, the magnitude of blood pressure affects the blood vessels and the filling resistance in the circulatory system. Increasing the amount of blood ejected by the heart, causing a rise in blood pressure.
Palpitations causes rise in blood pressure when the volume of blood ejected into the aorta during every systole, is not reduced. For the same reason, and the blood pressure rises with increasing stroke volume of blood ejected into the aorta at a constant heart rate. This may be, for example, by increasing the inflow of venous blood to the heart muscle during operation.
The muscular wall of the small and medium arteries – arterioles are in good shape, that is, in a state of some small cuts. Therefore arteries and arterioles, how to resist, called resistance vessels.
The degree of filling of the vascular system of blood due mainly constant current tone of the walls of blood vessels. The fall of the tone increases the capacity of the blood vessels and, hence, with the same mass of filler reduces blood circulatory system, leading to a fall in blood pressure.
The resistance to blood flow increases with the active reduction of arterial vessels. In this case, the blood pressure increases.
Especially great influence on blood pressure exerts constriction or dilation of arterioles in the abdominal cavity in which runs a considerable part of the total mass of blood. Increasing the viscosity of the blood increases the friction against the walls of the blood vessels and internal friction, i. e. resistance increases, and this leads to a rise in blood pressure.
Curve recording fluctuations in blood pressure wave three different orders.
The waves of first order, or pulse waves. Systole causes a rise in blood pressure during diastole and the blood pressure drops a bit. The pressure during systole is called systolic or maximum, and during diastole – diastolic or minimum.
The difference between systolic and diastolic pressures is called pulse pressure. Under equal conditions of pressure pulse dependent on the stroke volume. The farther from the heart, the pulse pressure is less. In the small arteries and capillaries of the pulse wave is not.
The waves of the second order – respiratory waves. Due to the increase of the suction action of the thoracic cavity during inspiration blood pressure at this time is increased by increasing blood flow to the heart. During exhalation, the blood pressure drops. These variations correspond to the respiratory movements of the chest and so they rarely pulse. One of the respiratory wave is noted several pulse waves.
Waves of the third order (Traube-Hering) due to variations in the regulation of vascular walls tone of the nervous system, ie. E. Rise and fall in blood pressure reflex increase or decrease of vascular tone. These waves are more sharply expressed during oxygen starvation of the brain. They are even less breathing. On the same page there are several third-order wave of second order. Most blood pressure in the cavities of the heart and aorta. In the brachial artery of an adult aged 20 to 40 years old in full physical and mental rest systolic pressure is 110-125 mm Hg. Art., Diastolic – 60-85 mm Hg. Art., and the difference between them, or pulse – 35 – 50 mm Hg. Art.
Blood pressure increases with age due to the increased size and weight. In 50 – 60 years of systolic pressure 125 -135 mm Hg. Art., Diastolic 80 – 90 mm Hg, p. In elderly women pressure slightly higher than that of older men.
Maximum systolic blood pressure in humans is about 16-18 hours, and minimum – from 2 to 4 am.
When ionizing radiation blood pressure drops due to the expansion of capillaries and blood loss, despite the quickening heartbeat. Muscle, work and emotions cause a rise in blood pressure, which in healthy people quickly returned to normal after cessation of work and emotions. Between the value of the body of animals and blood pressure have no dependencies.
Increasing the metabolism increases blood pressure.
As the distance from the left ventricle the blood pressure falls, because the energy of the heart, creates a pressure in the aorta, it is spent to overcome resistance in the circulatory system and blood flow. The large and medium arteries decreases the blood pressure by only 10%, and in the arterioles and capillaries – 85%.
In human aortic pressure is 120-140 mm Hg. Art., in major arteries – 110-125 mm Hg. st., in the small arteries – 70-90 mm Hg. st., in the arterioles – 40-60 mm Hg. st., in the capillaries – 20-40 mm Hg. v. in the large veins – 10-15 mm Hg. Art., in hollow veins during exhalation of 2-5 mm Hg. Art., and during inspiration due to the suction action of the thoracic cavity pressure by 3-7 mm Hg. Art. below atmospheric pressure. The veins of the lower extremities, on the contrary, the pressure increases during inspiration and decreases during expiration.
Long term, for many days, a drop in systolic pressure in the adult below 100 mm Hg. Art. denoted as hypotension and rise above 140 mm Hg. Art. – As hypertension.
Two different values of systolic pressure: End or sum of the potential and kinetic energy of the mass of the blood moving in a specific area of the vascular system, and a side, or the true value of the pressure at the blood vessel wall, which is less than the final.
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