lecture recording KINE 191- CARDIOVASCULAR

Cardiovascular System Overview

• Cardiovascular Definition:

  • Cardio means heart in Latin, and vascular refers to vessels, so cardiovascular refers to heart vessels.

Heart Anatomy

• Size and Location:

  • The heart is about the size of a closed fist, weighing approximately 300 grams in adults.

  • It rests on the diaphragm near the midline of the thorax within the mediastinum (the region between the sternum and thoracic vertebrae), tilted slightly towards the left side of the body.

• Heart Orientation:

  • The heart's apex points downwards, tilting to the left, while the base is positioned superior and more to the right.

  • Approximately two-thirds of the heart's mass lies to the left of the midline.

Heart Structure

• Layers of the Heart:

  • Pericardium: A double-walled sac surrounding the heart.

    • Fibrous pericardium: The outer layer made of inelastic tough tissue.

    • Serous pericardium: A thinner, double-layer membrane comprising the parietal and visceral layers, producing fluid for lubrication.

  • Heart Wall Layers:

    • Epicardium: The outer layer, also part of the serous pericardium, composed of connective tissue.

    • Myocardium: The thick muscular layer responsible for heart contractions.

    • Endocardium: The innermost layer, a thin layer of endothelial tissue lining the heart chambers.

Chambers of the Heart

• Structure:

  • Four chambers: two upper chambers called atria and two lower chambers called ventricles.

• Function:

  • Right Atrium: Collects deoxygenated blood from the body via the superior and inferior vena cavae.

  • Right Ventricle: Pumps deoxygenated blood to the lungs through the pulmonary valve.

  • Left Atrium: Receives oxygenated blood from the lungs through pulmonary veins.

  • Left Ventricle: Pumps oxygenated blood to the body through the aorta.

Heart Valves

• Types of Valves:

  • Atrioventricular valves: Bicuspid (mitral) valve and tricuspid valve are positioned between the atria and ventricles.

  • Semilunar valves: Pulmonary and aortic valves allow blood to exit the heart.

• Function of Valves:

  • Valves open and close to ensure one-way blood flow through the heart and prevent backflow.

Blood Flow Cycle

• Circulation Pathway:

  1. Deoxygenated blood returns to the right atrium from the body.

  2. Blood moves to the right ventricle, exiting via the pulmonary valve to the lungs.

  3. Oxygenated blood returns to the left atrium from the lungs.

  4. Blood moves to the left ventricle, exiting via the aortic valve to the body.

• Cardiac Cycle Phases:

  1. Atrial Systole: Atria contract, pushing blood into ventricles. P wave on EKG represents this.

  2. Ventricular Systole: Ventricles contract. QRS complex represents ventricular depolarization.

  3. Relaxation: Both atria and ventricles relax, allowing filling. T wave represents ventricular repolarization.

Electrical Conduction System

• Components:

  • Sinoatrial (SA) Node: Natural pacemaker located in the right atrium, initiates heartbeat and determines heart rate.

  • Atrioventricular (AV) Node: Electrical gateway between atria and ventricles, delays impulse for proper ventricular filling.

  • Bundle of His: Conducts impulses from the AV node to the ventricles.

  • Purkinje Fibers: Spread impulses throughout the ventricular myocardium.

• Action Potentials:

  • Pacemaker Function: The SA node generates impulses without external stimulation; regulates heart rate based on body activity levels.

  • Depolarization and Repolarization: Involves movement of sodium and potassium ions across membranes, leading to action potentials that propagate through cardiac tissue.

Electrocardiogram (EKG/ECG)

• Waveforms Representing Electrical Activity:

  • P Wave: Atrial depolarization.

  • QRS Complex: Ventricular depolarization and atrial repolarization (masked).

  • T Wave: Ventricular repolarization.

• Cardiac Cycle Representation:

  • EKG reflects the heart's electrical activity and can help diagnose arrhythmias or heart disease.

  • Understand how the EKG correlates with the mechanical phases of the cardiac cycle.