11+B-Cardiovascular+Physiology

Cardiovascular Physiology Overview

  • Lecturer: Dr. R. Ahangari

  • Institution: University of Central Florida, Orlando

  • Reference: Human Physiology by Linda S. Constanzo

Structure of the Heart

  • Key Structures:

    • Aortic Arch

    • Pulmonary Artery

    • Pulmonary Vein

    • Right Atrium

    • Left Atrium

    • Right Ventricle

    • Left Ventricle

    • Tricuspid and Bicuspid (Mitral) Valves

    • Chordae Tendineae

    • Papillary Muscles

    • Septum (separates left and right sides)

Heart Anatomy

  • Location: Between lungs in the chest

  • Layers:

    • Pericardium: Protective sac

    • Myocardium: Cardiac muscle responsible for contractions

  • Chambers of the Heart:

    • Four chambers: Left Atrium, Right Atrium, Left Ventricle, Right Ventricle

    • Left Ventricle: Largest and strongest chamber; pushes blood through the aortic valve.

Heart Valves Function

  • Types of Valves:

    1. Tricuspid Valve: Between right atrium and right ventricle

    2. Pulmonary Valve: From right ventricle to pulmonary arteries

    3. Mitral Valve: From left atrium to left ventricle

    4. Aortic Valve: From left ventricle into the aorta

Circulation Through the Heart

  • Process Overview:

    • Blood enters the heart at the right atrium → passes through the right AV valve → enters right ventricle

    • Right ventricle contracts → ejects blood through pulmonary valve → into pulmonary artery for oxygenation

    • Oxygenated blood returns via pulmonary veins to left atrium → enters left ventricle → pumped into the aorta to the body.

Systemic and Pulmonary Circulation

  • Systemic Circulation:

    • Carries oxygenated blood from the heart to the body and returns deoxygenated blood back to the heart.

    • Distributed through arteries, arterioles, and capillaries.

  • Pulmonary Circulation:

    • Transfers oxygen-depleted blood from the heart to the lungs and returns oxygenated blood back to the heart.

    • Red blood cells release CO2 and pick up O2 in the lungs.

Hemodynamics Overview

  • Vasculature Components:

    1. Arteries:

      • Thick-walled, under high pressure, carry oxygenated blood.

    2. Arterioles:

      • Smallest arteries, site of highest resistance, regulated by ANS.

    3. Capillaries:

      • Site of exchange (nutrients, gases); one cell thick.

    4. Venules:

      • Formed from merged capillaries; starts return to heart.

    5. Veins:

      • Return blood to the heart, thin-walled, under low pressure.

Blood Flow and Pressure Dynamics

  • Blood Flow Equation:

    • Q = P/R

    • Q = blood flow, P = pressure gradient, R = resistance.

  • Velocity of Blood Flow Equation:

    • V = Q/A

    • Higher velocity in larger vessels (like aorta) and lower in capillaries.

Resistance and Capacitance

  • Resistance Factors:

    • Poiseuille’s equation: R = 8 nl/r^4

  • Capacitance (compliance):

    • C = V/P; more compliant for veins than arteries.

Blood Vessel Pressure Profile

  • Pressure Trends:

    • Highest in aorta, lowest in vena cavae; major decreases across arterioles.

Arterial Pressure and Blood Pressure

  • Systolic and Diastolic Pressure:

    • Systolic: Highest during heart contraction.

    • Diastolic: Lowest when heart relaxes.

  • Pulse Pressure:

    • Difference between systolic and diastolic pressure.

  • Mean Arterial Pressure Calculation:

    • Approximately diastolic + 1/3 pulse pressure.

Venous and Atrial Pressures

  • Venous Pressure: Very low, high capacitance.

  • Atrial Pressure: Even lower than venous pressure; estimated via pulmonary wedge pressure.

Hypertension Overview

  • Types of Hypertension:

    1. Primary Hypertension: Unknown causes; linked to environmental factors like diet and stress.

    2. Secondary Hypertension: Caused by conditions affecting kidneys, arteries, heart or endocrine system.

Symptoms of Hypertension

  • Often asymptomatic; possible symptoms include:

    • Headaches, fatigue, shortness of breath, dizziness, nausea, blurred vision, palpitations, anxiety.

High Blood Pressure Treatments

  • Medications:

    • ACE inhibitors (e.g., Captopril), ARBs (e.g., Valsartan), Diuretics (e.g., Hydrochlorothiazide), Calcium channel blockers, Beta-blockers (e.g., Propranolol).

Cardiac Electrophysiology

  • Key Elements:

    • P wave, QRS complex, T wave; phases 0-4 of action potentials.

  • SA Node: Pacemaker; unstable resting potential, responsible for intrinsic heart rhythm.

Cardiac Action Potentials Phases

  • Phase 0: Upstroke due to Na+ influx in ventricles.

  • Phase 2: Plateau due to Ca2+ influx and K+ conductance.

  • Phase 3: Repolarization with K+ outflow.

  • Sinoatrial Node: Functions similarly to ventricles but based on Ca2+ currents.