Blood Pressure and Circulation

Blood Pressure Overview

• Blood pressure: Force exerted by blood against vessel walls.

• Potentially exists throughout vascular system but often refers to systemic arteries.

Arterial Blood Pressure

• Rises during ventricular contraction; falls during relaxation.

• Key measurements:

  • Systolic Pressure (SP): Max pressure during contraction.

  • Diastolic Pressure (DP): Min pressure before next contraction.

  • Pulse Pressure (PP): $PP = SP - DP$

  • Mean Arterial Pressure (MAP): $MAP = DP + \frac{1}{3} PP$

• Normally expressed as SP/DP (e.g., 120/80 mm Hg).

Factors Influencing Blood Pressure

• Blood volume increases → BP increases.

• Heart rate increases → CO and BP increase.

• Stroke volume (SV): Volume per contraction (~70 mL).

  • Cardiac output (CO): $CO = SV \times HR$

• Peripheral resistance (PR): Friction within vessels.

  • Increased PR raises BP (e.g., vasoconstriction).

• Viscosity: Resistance to flow; higher viscosity increases BP.

Blood Pressure Regulation

• Maintained via CO and PR: $BP = CO \times PR$

• Baroreceptors in aortic arch regulate BP through nerve signals.

Hypertension

• Defined as prolonged elevated BP, often asymptomatic.

• Causes: Increased Na+ intake, stress, obesity, kidney disease.

• Risks: Atherosclerosis, stroke, coronary issues.

• Treatment includes lifestyle changes and medications.

Circulatory Pathways

• Two circuits: Pulmonary (low O2, high CO2) and systemic (high O2).

• Major branches: Aorta provides systemic distribution.

Venous System

• Returns blood post gas exchange.

• Pathways less structured than arterial system, often parallels arteries.

• Major veins: Superior and Inferior Vena Cava.

Age-Related Changes in Cardiovascular Health

• Increased cholesterol, narrowed arteries, decreased elasticity.

• Variation in heart muscle and tissue composition.

Molecular Causes of Cardiovascular Disease

• Environmental and hereditary factors, e.g., Marfan syndrome, familial hypercholesterolemia.