Sinoatrial (SA) node

Definition

The sinoatrial (SA) node is a group of specialized cardiac cells located in the right atrium of the heart. It acts as the natural pacemaker, initiating electrical impulses that regulate heartbeats.

5 Must Know Facts For Your Next Test

1. The SA node generates electrical impulses at approximately 60-100 beats per minute under normal conditions.
2. It is located near the superior vena cava in the right atrium.
3. The SA node's activity is influenced by both the autonomic nervous system and hormonal signals.
4. It causes the atria to contract, pushing blood into the ventricles.
5. Malfunction of the SA node can lead to arrhythmias or require artificial pacemaker implantation.

Review Questions

• Where in the heart is the SA node located?
• What is the primary function of the SA node?
• How does autonomic nervous system influence SA node activity?

Related terms

Atrioventricular (AV) Node: A secondary pacemaker located between the atria and ventricles that delays impulses from the SA node before passing them to ventricles.

Bundle of His: A collection of heart muscle cells specialized for electrical conduction that transmits impulses from AV node to ventricles.

Electrocardiogram (ECG or EKG): A test that measures electrical activity of the heart to show changes in heart rhythm and detect abnormalities.