2.12 Blood Pressure | Blood Circulatory System Of Man | Biology 12

Blood pressure is a critical physiological parameter that reflects the efficiency of the cardiovascular system. It is closely linked to the Phases of Heartbeat→ and the Rate of Blood Flow→.

Definition: The force exerted by the blood against any unit area on the inner walls of a blood vessel.
Measurement:
- Standard reference: Mercury (Hg) manometer (Sphygmomanometer).
- Unit: Millimetres of mercury (mm Hg).
- Explanation: A reading of 100 mm Hg means the pressure is sufficient to lift a column of mercury 100 mm high.

Types of Arterial Blood Pressure

Arterial blood pressure fluctuates in response to the cardiac cycle.

Systolic Pressure

Definition: The highest arterial blood pressure recorded during the cardiac cycle.
Occurrence: Occurs when the ventricles of the heart contract (systole), forcefully pushing blood into the aorta and pulmonary arteries.

Diastolic Pressure

Definition: The lowest arterial blood pressure recorded during the cardiac cycle.
Occurrence: Occurs when the ventricles of the heart relax (diastole) and are filling with blood from the atria.

Factors Affecting Blood Pressure

Blood pressure is not static and is regulated by several factors, including peripheral resistance and blood volume. Regulation is often mediated by Baroreceptors→.

Peripheral Resistance: The friction between blood and the walls of the blood vessels. Vasoconstriction increases resistance and BP, while vasodilation decreases it.
Cardiac Output: The volume of blood pumped by the heart per minute.
Blood Volume: Regulated largely by the kidneys; a decrease in volume (e.g., dehydration) leads to a decrease in BP.

Clinical Significance

Monitoring blood pressure is essential for diagnosing Cardiovascular Disorders→.

Hypertension: Persistent high blood pressure (usually above 140/90 mmHg), which can lead to Heart Problems→ or stroke.
Hypotension: Abnormally low blood pressure.
Kidney Function: Blood pressure significantly impacts the Functions of the Kidney→, specifically the glomerular filtration rate.

Types of Arterial Blood Pressure

Arterial blood pressure fluctuates in response to the cardiac cycle.

Definition: The highest arterial blood pressure recorded during the cardiac cycle.

Occurrence: Occurs when the ventricles of the heart contract (systole), forcefully pushing blood into the aorta and pulmonary arteries.

Definition: The lowest arterial blood pressure recorded during the cardiac cycle.

Occurrence: Occurs when the ventricles of the heart relax (diastole) and are filling with blood from the atria.

Factors Affecting Blood Pressure

Blood pressure is not static and is regulated by several factors, including peripheral resistance and blood volume. Regulation is often mediated by Baroreceptors→.

Peripheral Resistance: The friction between blood and the walls of the blood vessels. Vasoconstriction increases resistance and BP, while vasodilation decreases it.

Cardiac Output: The volume of blood pumped by the heart per minute.

Blood Volume: Regulated largely by the kidneys; a decrease in volume (e.g., dehydration) leads to a decrease in BP.

Clinical Significance

Monitoring blood pressure is essential for diagnosing Cardiovascular Disorders→.

Hypertension: Persistent high blood pressure (usually above 140/90 mmHg), which can lead to Heart Problems→ or stroke.

Hypotension: Abnormally low blood pressure.

Kidney Function: Blood pressure significantly impacts the Functions of the Kidney→, specifically the glomerular filtration rate.