How is blood pressure produced?
Every tissue in the human body needs to take in nutrients from the blood during metabolism and discharge metabolites into the blood. Blood vessels are the only channel for transporting blood. The heart pumps blood into the arteries, which creates pressure on the walls of the blood vessels. Therefore, the arterial blood vessel wall is usually thicker and more elastic and has greater internal pressure, and it is also the source of blood pressure.
Blood pressure refers to the lateral pressure on the blood vessel wall per unit area when blood flows in the blood vessels, and it is the driving force that promotes the blood flow in the blood vessels. In different blood vessels, blood pressure has names. The blood pressure measured in arterial blood vessels is arterial blood pressure, and the blood pressure measured in capillaries is capillary pressure. Similarly, blood pressure measured in venous blood vessels is called venous pressure.
Generally speaking, blood pressure refers to the blood pressure of the thick arteries near the heart - the brachial artery blood pressure is usually measured with a sphygmomanometer and NIBP cuff.
How our blood pressure change within 24 hours?
In general, Our blood pressure fluctuates within 24 hours, showing the form of two peaks and one valley. The first peak occurs at 8-10 in the morning, and the second at 3-5 in the afternoon. After entering sleep at night, the blood pressure gradually decreases, and it drops to the lowest point at 3-4 at night.
Sometimes we measure blood pressure once in a while and get shocked when we see the blood pressure reading because it may belong to the category of first-level hypertension by comparing the blood pressure classification table. It needs to be reminded here that a single blood pressure value has no clinical significance. Blood pressure not only fluctuates within 24 hours but also is higher when in fatigue, tension, excitement, satiation, etc. However, fatigue, tension, and satiety are only the values that affect blood pressure measurement, not the fundamental factors affecting blood pressure.
What are the underlying factors that affect blood pressure?
Circulating blood volume
Circulating blood volume refers to the total amount of circulating blood in the human body, which is the premise for arterial blood pressure. Here, it refers specifically to the effective circulating blood volume. Because a part of human blood is in the liver, spleen, and lymphatic sinuses, and a small amount is in the capillaries, so not all the blood in the body circulates in the blood vessels.
When a valid circulating blood volume increases, the pressure on the blood vessel wall rises, and the blood pressure is also higher.
Myocardial contractility
In the case of a constant heart rate, the stronger the myocardial contractility is, the more blood the heart pumps. People who often exercise have a more developed myocardium, stronger contractility, and more powerful ability of the heart to pump blood.
If there is no resistance to the energy released by the myocardial contraction, it will all convert into the blood kinetic energy. Due to the peripheral resistance in the blood vessels, part of the energy becomes the blood kinetic energy, and part of it forms the lateral pressure on the vessel wall.
Peripheral vascular resistance
Peripheral vascular resistance is a reason for the formation of blood pressure, but too much resistance is not a good thing. Many middle-aged and elderly have atheromatous plaques in their blood vessels. Greasy and irregular diets, smoking, drinking, and poor emotions can increase blood viscosity.
Increased blood viscosity undoubtedly increases peripheral vascular resistance and is prone to local vascular occlusion. Under the condition that circulating blood volume, myocardial contractility, and vascular wall elasticity remain unchanged, people with relatively large peripheral vascular resistance will have higher blood pressure.
Arterial wall elasticity
Although the ventricle intermittently ejects blood, the blood flowing in the artery is continuous. It is due to the peripheral vascular resistance effect and the elasticity of the arterial wall. When the ventricle ejects blood, about one-third of the blood flows to the periphery, and the remaining two-thirds are in the aorta and aorta, which increases the aortic pressure.
People who eat lightly and exercise regularly have better blood vessel elasticity and relatively stable blood pressure, and vice versa.
The above is about several fundamental physiological factors that affect blood pressure. Others such as drinking, obesity, smoking, mental stress, lack of exercise, and salty taste are superficial reasons. Of course, these inconspicuous reasons will eventually affect fundamental factors such as myocardial contractility, blood vessel thickness, and circulating blood volume.
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