Respiration and Circulation — BIOLOGY STD 12 Science — Question
Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYRespiration and Circulation4 Marks
Question
Explain in brief the factors affecting blood pressure.
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Answer
Cardiac output : Normal cardiac output is 5 lit/min. Increase in cardiac output increases systolic pressure.
Peripheral resistance : Peripheral resistance depends upon the diameter of blood vessels. Decrease in diameter of arterioles and capillaries under the effect of vasopressin cause increase in peripheral resistance and thereby increase in blood pressure.
Blood volume : Loss of blood in accidents decreases blood volume and thus cause decrease in blood pressure.
Viscosity of blood : Blood pressure is directly proportional to viscosity of blood.
Age : Blood pressure increases with age due to increase in inelasticity of blood vessels.
Venous return : Amount of blood brought to the heart via the veins per unit time is called the venous return and it is directly proportional to blood pressure.
Length and diameter of blood vessels : Blood pressure is directly proportional to the total length of the blood vessel. Blood pressure can also be affected by vasoconstriction or vasodilation.
Gender : Females have slightly lower BP than males of her age before menopause. However, the risk of high B. P increases in the females after menopause sets in.
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