Understanding the Cardiovascular System Basics

Sep 10, 2024

Cardiovascular System - Anatomy and Physiology Review

Overview

  • Presented by Cathy from Level Up RN.
  • Focus on heart conduction system, cardiac function, and blood pressure.
  • Includes a quiz to test understanding.

Heart Conduction System

  • SA Node (Sinus Node): Initiates electrical impulse, causing atria to depolarize and contract.
  • AV Node: Delays impulse to allow atria to empty into ventricles.
  • Impulse Pathway:
    • From AV Node → Bundle of His → Left & Right Bundle Branches → Purkinje Fibers.
  • Result: Depolarization of the myocardium; triggers ventricular contraction.
  • Important for understanding dysrhythmias.

Cardiac Function

  • Cardiac Cycle:
    • Diastole: Ventricles and atria are relaxed and fill with blood.
    • Systole: Ventricles and atria contract and eject blood.
    • Time Distribution: 2/3 in diastole, 1/3 in systole.
  • Cardiac Output:
    • Volume of blood ejected from left ventricle per minute.
    • Calculated as Heart Rate x Stroke Volume.
    • Adult range: 4-8 liters/minute.
  • Left Ventricular Ejection Fraction (LVEF):
    • Percentage of blood leaving left ventricle per contraction.
    • Healthy range: 55%-70%.
  • Preload vs. Afterload:
    • Preload: Volume of blood in ventricles at end of diastole, affecting myocardial fiber stress.
    • Afterload: Peripheral resistance to overcome for systemic circulation.
    • Medications in heart failure aim to reduce preload/afterload.

Blood Pressure

  • Components: Systolic and Diastolic Blood Pressure.
    • Systolic Blood Pressure: Pressure during ventricular contraction.
    • Diastolic Blood Pressure: Pressure during ventricular relaxation.
  • Regulation by Autonomic Nervous System:
    • Based on inputs from baroreceptors, chemoreceptors, and stretch receptors near heart.

Quiz Questions

  1. Cardiac Output Calculation: Heart Rate x Stroke Volume.
  2. Volume of Blood at End of Diastole: Preload.
  3. Percentage of Blood Leaving Left Ventricle per Contraction: Left Ventricular Ejection Fraction (LVEF).

Conclusion

  • Next video: AMP concepts related to the hematologic system.
  • Encouragement to like, comment, and subscribe for more nursing content.