There are various factors that maintain normal blood pressure in humans. They are called blood pressure determinants. Here, let us discuss such factors that maintain blood pressure.
Table of Contents
Determinants of Blood Pressure
Some factors are necessary to maintain normal blood pressure. These factors are called mechanical factors, local factors or determinants of blood pressure.
The different types of local or mechanical factors that regulate blood pressure are divided into two types:
- Central factors – pertaining to the heart
- Heart rate
- Cardiac output
- Peripheral factors – pertaining to blood and blood vessels
- Peripheral resistance
- Velocity of blood flow
- Elasticity of blood vessels
- Blood volume
- Venous return
- Viscosity of blood
- Diameter of blood vessels
Central Factors
Cardiovascular Output
Systolic pressure and cardiac output are directly correlated. Systolic pressure rises whenever cardiac output rises; conversely, when cardiac output falls, systolic pressure falls. Cardiac output rises during physical activity, emotional stress, etc. Hence, the systolic pressure also rises under these circumstances. Systolic pressure falls as cardiac output diminishes, as it does in circumstances like myocardial infarction.
Heart Rate
Insignificant changes in heart rate have little impact on arterial blood pressure. However, a significant change in heart rate has an impact on blood pressure through changing cardiac output.
Peripheral Factors
Peripheral Resistance
The crucial element that keeps the diastolic pressure constant is peripheral resistance. The resistance put up against blood flow at the periphery is known as peripheral resistance. Peripheral resistance is directly correlated with diastolic pressure.
Arterioles, often known as the resistant vessels, provide this resistance. Diastolic pressure rises with rising peripheral resistance, while diastolic pressure falls with falling peripheral resistance.
Blood Flow
Blood volume and blood pressure are directly proportional.
Blood volume regulates blood pressure through cardiac output and venous return. An increase in blood volume causes an increase in cardiac output and venous return, which elevates blood pressure.
Venous Return
Arterial blood pressure is directly related to venous return. When venous return increases, there is an increase in cardiac output and ventricular filling, which results in an elevation of blood pressure.
Elasticity of Blood Vessels
Arterial blood pressure is inversely correlated with the elasticity of blood vessels. Blood vessels are distensible in nature and can maintain pressure due to their elastic characteristics. When the elastic property is lost, the blood vessels become rigid (arteriosclerosis) and pressure increases, especially in old age. Deposition of cholesterol, fatty acids and calcium ions produces rigidity of blood vessels and atherosclerosis, leading to increased blood pressure.
Velocity of Blood Flow
Pressure in a blood vessel is directly related to the velocity of blood flow. If the velocity of blood flow increases, the resistance is increased. So, the pressure is increased.
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Diameter of Blood Vessels
Arterial blood pressure is inversely correlated with the diameter of the blood vessel. When the diameter of blood vessels reduces, the peripheral resistance goes up, which invariably raises blood pressure.
Viscosity of Blood
Arterial blood pressure and the viscosity of blood are directly proportional to each other. When the viscosity of blood increases, the frictional resistance is increased and this increases the blood pressure.
|
Arterial Blood Pressure |
Factors |
|
Arterial blood pressure is directly proportional to |
Heart rate Cardiac output Viscosity of blood Velocity of blood flow Blood volume Venous return Peripheral resistance |
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Arterial blood pressure is inversely proportional to |
Diameter of blood vessel Elasticity of blood vessel |
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