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.