Factors affecting blood pressure:
- Blood volume.
- Cardiac output
- Peripheral resistance.
- The elasticity of blood vessels.
- The diameter of the lumen of blood vessels.
- The viscosity of blood.
Blood volume: it’s the total amount of blood in circulation. A sufficient amount of blood in blood vessels is necessary to maintain normal blood pressure loss of blood as in hemorrhage produces a fall in blood pressure.
Cardiac output is the quantity of blood pumped by the heart in one minute. It’s the product of stroke volume and the heart rate. An increase in stroke volume increases systolic blood pressure. An increase in cardiac output increases both systolic and diastolic blood pressure.
Peripheral resistance: is the resistance offered by blood vessels for the flow of blood. Resistance is offered mainly by small blood vessels, especially arterioles.
Elasticity of the arterial walls distends the aorta when the ventricle contracts. The elastic recoils when the ventricle relaxes. This recoiled pushes the blood onwards. The decrease in elasticity as in atheroma produces a rise in blood pressure. 50 The diameter of the lumen of blood vessels: can be altered, narrowing of the lumen increases the resistance to blood flow and this increases blood resistance to blood flow and this increases blood pressure. Enlargement of the lumen has the opposite effect.
The viscosity of blood: it’s the blood stickiness. The viscosity of blood spends on plasma, plasma proteins and number of the red blood cells. An increase in viscosity increases blood pressure.