Question

select the correct answer. an individual’s ekg shows changes in atrial contraction. which image shows contraction of the atria?

Explanation:

To determine which image shows atrial contraction, we analyze the heart's electrical and mechanical events:

1. Atrial Contraction (Atrial Systole): During atrial contraction, the atria (upper heart chambers) contract to push blood into the ventricles. This occurs after the electrical signal from the sinoatrial (SA) node spreads through the atria, and the atrioventricular (AV) node is activated (but before ventricular contraction).

1. Analyzing the Images:

• The first image (left) shows electrical activity spreading through the atria (arrows in the atria) and the AV node, consistent with atrial contraction. The atria are actively contracting to pump blood into the ventricles, while the ventricles are relaxed (pre - ventricular contraction).
• The second and third images show ventricular contraction (arrows in the ventricles), as the electrical activity and mechanical contraction are focused on the lower chambers (ventricles).

Answer:

The first (left - most) image shows contraction of the atria.