Electrocardiographs (ECGs or EKGs) Provide Data About the Electrical Activity

Multiple Choice

Electrocardiographs (ECGs or EKGs) provide data about the electrical activity of the heart. By placing a series of "leads" on a person's chest, the electrical activity of the heart can be recorded and analyzed in order to detect irregular heartbeats (arrhythmias) and other conditions. The figure below shows a normal EKG tracing for one cardiac cycle.
The P region represents electrical activity spreading through the atria. The QRS region represents electrical activity spreading through the ventricles. The T region represents electrical activity in the ventricles returning to rest.
-What is happening in the heart during the QRS region?

A) The atria are filling with blood.
B) The ventricles are filling with blood.
C) The atria are contracting.
D) The ventricles are contracting.