heartcycle 1

Overview of Cardiovascular System

• Focus on cardiovascular system due to its impact on mortality rates.

• Significance of understanding blood vessels and blood pressure.

Anatomy of the Heart

• Structure: Heart is divided into chambers.

  • Atria: Top chambers of the heart.

    • Left atrium (labeled).

    • Right atrium (located on the opposite side).

  • Ventricles: Bottom chambers of the heart.

    • Left ventricle.

    • Right ventricle.

• Heart dissection: Front of the heart removed for internal view, essential for lab work.

Electrical Conducting System

• Representation in diagrams: Yellow elements show the electrical conducting system.

• Sinoatrial (SA) Node:

  • The pacemaker of the heart where electrical excitation begins.

  • Generates action potentials independently without external nervous system input.

• Atrioventricular (AV) Node:

  • Located between atria, situated at the bottom of the right atrium.

  • Receives signals from the SA node; embedded within the atrial wall.

• AV Bundle (Bundle of His):

  • Takes signals from the AV node.

  • Thin structure that runs down the septum between the ventricles.

• Bundle Branches:

  • Two branches (left and right) extending down each side of the septum.

• Purkinje Fibers:

  • Spread electrical signals throughout the ventricles, facilitating contraction.

  • The contraction begins at the apex of the heart and moves upward toward the atria.

Contraction Mechanism

• Directional Flow of Blood:

  • Ventricles push blood upwards (to aorta and pulmonary trunk), atria push it downwards.

  • This process resembles squeezing a tube of toothpaste.

• The contraction sequence is crucial for effective blood circulation.

Electrocardiogram (ECG/EKG)

• Used to study heart's electrical activity.

• Origin of terms:

  • EKG comes from "Kardiogramm" in German; ECG is the English equivalent.

• Key Components of ECG:

  • P Wave: Atrial electrical excitation (smallest wave).

  • QRS Complex: Signifies ventricular excitation and is the most significant part of the ECG.

  • T Wave: Indicates ventricular repolarization.

• Importance of recording good quality waveform for practical understanding in lab sessions.

Cardiac Cycle and Electrical Excitation

• Cycle Overview:

  • Sequence of electrical excitation and subsequent contraction.

  • P wave (atrial excitation) leads to contraction.

  • QRS complex (beginning of ventricular excitation) observed next.

  • T wave indicates return to resting state after ventricular contraction.

• The entire process repeats continuously in the cardiac cycle.

Blood Flow Pathway Through the Heart

• Systematic Flow:

  • Blood flows from the body into the right atrium via the vena cava.

  • Moves through the right atrium, passes through the tricuspid valve (right AV valve) into the right ventricle.

  • Exit to lungs through the pulmonary valve into the pulmonary trunk.

• Oxygenation Process:

  • Blood becomes oxygenated in lungs, returns to the left atrium via pulmonary veins.

  • Passes to the left ventricle via the mitral valve (left AV valve) and exits through the aortic valve into the aorta.

Coronary Circulation

• Supplies blood to the heart tissue itself.

• Coronary Arteries:

  • First branches off the aorta, responsible for heart muscle perfusion.

• Importance of coronary circulation in overall heart health.