Table of Contents
About Blood Pressure
Blood pressure: Tissues in the body need oxygen and nutrients to stay alive and function properly. The heart fulfills this need by supplying oxygen and nutrient-rich blood throughout the body.
Blood cannot reach tissues in the body through blood vessels unless it is pushed under some pressure. The heart exerts the necessary pressure from its pumping system to force blood into the blood vessels. To do this, the heart undergoes continuous contractions. Blood is pumped into the heart each time the heart contracts. This pumped blood circulates throughout the body through blood vessels.
The pressure exerted on the blood while flowing in the blood vessels is called ‘B.P. pressure.‘ The blood pressure when the heart is relaxed is called diastolic blood pressure.
Factors Affecting B.P
Just as water exerts pressure on plants through a rubber pipe (hose pipe) used to water plants in the garden, pressure also exerts pressure on the blood flowing through our blood vessels.
This pressure on the blood decreases when the arteries closer to the heart are larger and away from the heart to other parts of the body. It is because of this difference in circulation that blood flows to all parts of our body.
In this way, the blood flows less from the most inflamed parts of the body and returns to the heart.
It flows into the organs and returns to the heart.
Control of blood pressure in every human depends on three things.
1. Depending On The Speed At Which The Heart Beats (Heart Rate):
Heart rate is measured by the number of heartbeats per minute. The speed at which the heart beats is called the heart rate. Increases whenever blood pressure rises. Decreases when blood pressure drops.
- Heart rate speed depends on various factors. Important among them are:
- Nervous system in the body
- Those released in the body are called chemical carriers. These are called ‘hormones.’
- Body temperature
- Medicines used
- Compelling diseases
– All these affect the ‘heart rate.’
2. How Much Blood The Heart Pumps During Each Stroke (Stroke Volume):
Stroke volume is the volume of blood pumped from the lower chamber of the heart during each stroke. The stroke volume of a ventricle when you are resting is equal to the volume of blood entering the heart through the veins. But when you are under stress (stressful situations), your nervous system makes the heart beat faster, and the lower layers of the heart pump out more blood. Stroke volume increases.
The lower chambers of the heart (ventricles) also pump more blood for the following reasons (increasing stroke volume).
- Some hormones are released in the body
- Due to drugs used
- Due to various diseases
- Depending on the amount of blood in the body (this is called blood volume)
3. How Difficult Is It For Blood To Flow Throughout The Body:
(This is called peripheral resistance) :
This third factor affecting B.P. depends on the width of the arteries through which the blood flows. Blood encounters more resistance when coming through narrow blood vessels than through wide blood vessels.
The blood pumped by the heart can vary abnormally in different situations depending on what the person is doing. The reason for that is that in those cases, his body opens the arteries wide or narrow according to its needs and to ensure that the B.P. does not rise or fall abnormally.
This type of adjustment of blood vessel width to match the way the heart pumps blood is called peripheral resistance. As blood circulates throughout the body, it encounters most of this resistance in small arteries called arterioles.
The walls of these small arteries are lined with specialized smooth muscle. They have the ability to dilate quickly and return to normal quickly. This ability allows small blood vessels to dilate or collapse more easily.
B.P. Control
Our nervous system regulates B.P. according to the needs and demands of the body under different conditions. For example:
- While resting
- While sleeping
- When at rest
In such cases, the nervous system keeps B.P. low in us; similarly, in cases where the nervous system keeps B.P. high in us, viz.
- While exercising
- While working hard
- When in anger
- When under stress.
The amount of water (fluids) and salts (salt) in the body and how much they are excreted also affects B.P.
If there is more water and salt in the body, B.P. increases. Aldosterone, a hormone secreted by the anal glands, controls the excretion of salts by the kidneys. Excessive release of this hormone (aldosterone) causes salts and water to remain inside the body without being excreted. Blood volume increases when salts and water are retained too much. When blood volume is high, the heart has to work harder to circulate blood throughout the body. As a result, B.P. increases. Renin, a substance released by the kidneys, is converted to angiotensin. An excess of angiotensin causes the blood vessels to constrict. This leads to the overproduction of aldosterone. Thereby causing an increase in B.P.