Cardiovascular System (CVS) Notes

Dr Haruko Okamoto - C1102: Physiology and Disease Lecture 4: The Cardiovascular System (CVS) - Autumn 2025

Overview of the Course

Topic: Cardiovascular System (CVS)

  • Instructor: Dr. Haruko Okamoto

  • Lecture: Physiology and Disease, C1102, Autumn 2025

Functionality of the Cardiovascular System

Main Purposes of the CVS

  • Oxygen Transport: Provides oxygen to tissues.

  • Nutrient Distribution: Transports nutrients throughout the body.

  • Water Delivery: Ensures hydration by moving water to and from cells.

  • Immune Response: Distributes immune cells and antibodies to fight infections.

  • Clotting Factors: Transports clotting proteins necessary for wound healing.

  • Hormonal Transport: Moves hormones and signals across the body.

  • Waste Removal: Carries bodily waste products for excretion.

  • Red Blood Cell Functionality: Facilitates the removal of carbon dioxide (CO2) from tissues.

Components of the CVS

  1. Heart: Functions as a pump to circulate blood.

  2. Blood Vessels: Comprises arteries, veins, and capillaries that comprise the circulatory system.

  3. Blood: The fluid that circulates in the system, carrying nutrients and waste.

Conducting System of the Heart

Myocardial autorhythmic and contractile cells

  • Sino-Atrial (SA) Node: The primary pacemaker of the heart, generating electrical impulses.

  • Atrioventricular (AV) Node: The secondary pacemaker that slows down the impulse before it reaches the ventricles, ensuring proper timing of contraction.

  • Intercalated Discs: Facilitate communication between cardiac cells via gap junctions, which allow rapid transmission of action potentials.

Sequence of Electrical Signaling Events during One Cardiac Cycle

1. Action Potentials of Autorhythmic Cells

  • SA Node Activation: Initiates depolarization, leading to a contraction signal.

2. Action Potentials of Contractile Cells

  • Depolarization Spread: The electrical signal spreads through the atria and subsequently to the ventricles through the Purkinje fibers.

Electrocardiogram (ECG)

Typical Human ECG Features

  • P Wave: Represents atrial depolarization.

  • QRS Complex: Signifies ventricular depolarization; typically a sharp peak.

  • T Wave: Corresponds to ventricular repolarization; a gentle transition back to baseline.

  • Measurements: 5 mm represents 1 second; heart rate is calculated as follows:
    HR = \frac{60 \text{ sec}}{\text{Time of one cardiac cycle in seconds}}

Cardiac Cycle Definition

1. Definition of Cardiac Cycle

  • Defined from one P-wave to the subsequent P-wave or alternatively from R-R peaks.

2. Heart Rate Calculation

  • Example: For a cardiac cycle time of 800 milliseconds,
    HR = \frac{60}{0.8} = 75\text{ bpm}

Blood Flow Sequence in One Cardiac Cycle

Processes Involved

  1. Diastole: All muscles relaxed, blood flows into atria and ventricles.

  2. Atrial Systole: Atria contract, pushing blood into ventricles.

  3. Ventricular Depolarization: Ventricles fill with blood; AV valves close to prevent backflow.

  4. Ventricular Ejection: Ventricles contract, exceeding arterial pressure, and eject blood into the aorta and pulmonary arteries.

  5. Isovolumetric Relaxation: Ventricles relax, pressure falls, semilunar valves close.

Heart Sounds

  • **S1 (