Answer
The pacemaker of the heart, which generates the electrical impulses that initiate each heartbeat and set the heart's rhythm, is located in the **sinoatrial (SA) node**. The SA node is situated in the upper wall of the right atrium.
The electrical excitation generated in the SA node travels through the heart's conduction system to reach the cardiocytes (muscle cells) of the left ventricle. Here's the path of electrical excitation, naming each component of the conduction system along the way:
1. **Sinoatrial (SA) Node:** The SA node, located in the upper wall of the right atrium, generates the initial electrical impulse. It's often referred to as the heart's natural pacemaker due to its role in initiating the heartbeat.
2. **Atria:** The electrical impulse spreads across both atria, causing them to contract and push blood into the ventricles.
3. **Atrioventricular (AV) Node:** The electrical signal reaches the AV node, located at the base of the right atrium near the septum. The AV node acts as a delay mechanism, allowing the ventricles time to fill with blood from the atria before contracting.
4. **Bundle of His (Atrioventricular Bundle):** From the AV node, the electrical impulse travels down the bundle of His, a bundle of specialized conducting fibers that extends into the interventricular septum.
5. **Right and Left Bundle Branches:** The bundle of His divides into right and left bundle branches, which run along the interventricular septum toward the apex of the heart.
6. **Purkinje Fibers:** The bundle branches further divide into smaller fibers known as Purkinje fibers. These fibers spread throughout the walls of the ventricles.
7. **Ventricles:** The electrical impulse rapidly travels through the Purkinje fibers, causing the ventricles to contract from the bottom upward. This coordinated contraction pushes blood out of the heart and into the circulation.
8. **Cardiocytes of the Left Ventricle:** The electrical excitation reaches the cardiocytes (muscle cells) of the left ventricle, stimulating them to contract and pump oxygenated blood into the aorta and subsequently to the rest of the body.
In summary, the electrical pathway starts at the SA node in the right atrium, travels through the atria, AV node, bundle of His, bundle branches, Purkinje fibers, and finally reaches the cardiocytes of the left ventricle, resulting in the coordinated contraction of the heart chambers and the pumping of blood throughout the body.
Work Step by Step
The pacemaker of the heart, which generates the electrical impulses that initiate each heartbeat and set the heart's rhythm, is located in the **sinoatrial (SA) node**. The SA node is situated in the upper wall of the right atrium.
The electrical excitation generated in the SA node travels through the heart's conduction system to reach the cardiocytes (muscle cells) of the left ventricle. Here's the path of electrical excitation, naming each component of the conduction system along the way:
1. **Sinoatrial (SA) Node:** The SA node, located in the upper wall of the right atrium, generates the initial electrical impulse. It's often referred to as the heart's natural pacemaker due to its role in initiating the heartbeat.
2. **Atria:** The electrical impulse spreads across both atria, causing them to contract and push blood into the ventricles.
3. **Atrioventricular (AV) Node:** The electrical signal reaches the AV node, located at the base of the right atrium near the septum. The AV node acts as a delay mechanism, allowing the ventricles time to fill with blood from the atria before contracting.
4. **Bundle of His (Atrioventricular Bundle):** From the AV node, the electrical impulse travels down the bundle of His, a bundle of specialized conducting fibers that extends into the interventricular septum.
5. **Right and Left Bundle Branches:** The bundle of His divides into right and left bundle branches, which run along the interventricular septum toward the apex of the heart.
6. **Purkinje Fibers:** The bundle branches further divide into smaller fibers known as Purkinje fibers. These fibers spread throughout the walls of the ventricles.
7. **Ventricles:** The electrical impulse rapidly travels through the Purkinje fibers, causing the ventricles to contract from the bottom upward. This coordinated contraction pushes blood out of the heart and into the circulation.
8. **Cardiocytes of the Left Ventricle:** The electrical excitation reaches the cardiocytes (muscle cells) of the left ventricle, stimulating them to contract and pump oxygenated blood into the aorta and subsequently to the rest of the body.
In summary, the electrical pathway starts at the SA node in the right atrium, travels through the atria, AV node, bundle of His, bundle branches, Purkinje fibers, and finally reaches the cardiocytes of the left ventricle, resulting in the coordinated contraction of the heart chambers and the pumping of blood throughout the body.
