Chapter 2: Anatomy And Physiology Of The Heart

When you’re dealing with cardiac emergencies, knowing how the heart works isn’t just helpful; it’s essential. This chapter of your ACLS Certification Course breaks down the heart’s structure and electrical system so you can better understand what’s behind the rhythms you see on a monitor.

How the Heart Is Built

The heart is a hollow muscle with four chambers that work together to keep blood moving through the body.

• The atria are the upper chambers that receive blood
• The ventricles are the lower chambers that pump blood out
• A thin wall called the septum separates the left and right sides

Here’s how blood flows through the heart:

•  The right atrium and ventricle carry oxygen-poor blood from the body to the lungs
• The left atrium and ventricle move oxygen-rich blood from the lungs to the body

Heart Physiology

The cells in the heart muscle can generate and respond to electrical signals without outside input. These impulses make the heart contract.

The signal follows this path:

• Starts in the SA node (sinoatrial node) in the right atrium, which acts as the heart’s pacemaker
• Travels to the AV node (atrioventricular node), where it pauses briefly
• Moves through the Purkinje fibers, which stimulate the ventricles to contract

This entire electrical cycle shows up on an electrocardiogram (ECG or EKG). It’s a common tool used to check how the heart is functioning and to detect possible problems.

An ECG can help:

• Identify causes of chest pain, such as inflammation, angina, or a heart attack

• Detect symptoms related to heart disease
• Show whether medications or treatments are working

To read an ECG accurately, it’s important to understand what a normal rhythm looks like.

Each heartbeat creates a repeating wave pattern, made up of several parts:

• P wave—shows activity in the atria
• QRS complex—represents the depolarization (contraction) of the ventricles
• T wave—shows repolarization (recovery) of the ventricles
• PR interval—the time it takes for the signal to move from the SA node to the AV node

This chapter in your online ACLS course gives you the foundation you’ll need to understand ECG rhythms and respond to cardiac events with confidence.