Cardiac Conduction System
Cardiac Conduction System
Notes
Sinoatrial Node (SA Node)
Located in the upper wall of the right atrium, near the superior vena cava entry point.
Function: Acts as the heart’s pacemaker, spontaneously generating electrical impulses that spread across the atria to cause atrial systole.
Autonomic Nervous System Influence:
- Sympathetic stimulation: Increases the firing rate and heart rate.
- Parasympathetic stimulation: Decreases the firing rate and heart rate.
Atrioventricular Node (AV Node)
Located in the atrioventricular septum, near the opening of the coronary sinus.
Function: Delays the electrical impulse by approximately 120ms to ensure complete atrial emptying before ventricular systole.
Atrioventricular Bundle (Bundle of His)
Continuation of the AV node, located in the interventricular septum.
Function: Transmits impulses to the Purkinje fibres after dividing into:
- Right bundle branch: Supplies the right ventricle.
- Left bundle branch: Supplies the left ventricle.
Purkinje Fibres
Located in the subendocardial ventricular walls.
Function: Rapidly conduct impulses for coordinated ventricular contraction, ensuring blood is ejected into the pulmonary artery and aorta.
Flashcard Questions
Q1: Where is the sinoatrial (SA) node located?
The SA node is located in the upper wall of the right atrium, near the junction of the superior vena cava.
Q2: What is the function of the sinoatrial (SA) node?
The SA node functions as the heart’s pacemaker, generating electrical impulses that initiate atrial systole.
Q3: How does the autonomic nervous system affect the SA node?
Sympathetic stimulation increases the SA node’s firing rate, raising the heart rate, while parasympathetic stimulation decreases it.
Q4: What is the role of the atrioventricular (AV) node?
The AV node delays electrical impulses by 120ms, allowing the atria to empty blood into the ventricles before ventricular systole.
Q5: Where is the atrioventricular (AV) bundle located?
The AV bundle descends through the interventricular septum and divides into the right and left bundle branches.
Q6: What are the Purkinje fibres, and where are they located?
The Purkinje fibres are located in the subendocardial surface of the ventricular walls and rapidly conduct impulses for ventricular contraction.
Q7: Why are Purkinje fibres efficient in conduction?
Purkinje fibres are rich in glycogen and have extensive gap junctions, enabling rapid conduction of electrical impulses.
Q8: What happens during atrial systole?
During atrial systole, blood is pushed from the atria into the ventricles.
Q9: What ensures the ventricles contract in a coordinated manner?
The Purkinje fibres rapidly transmit electrical impulses across the ventricles, ensuring synchronized contraction.
Q10: Which vessels receive blood during ventricular systole?
Blood is ejected into the pulmonary artery (from the right ventricle) and the aorta (from the left ventricle) during ventricular systole.