ECG and Cardiac Cycle Specifics

Question 1

P Wave

Answer 1

Atrial depolarization. The positive wave of depolarization spreads from the SA node and is conducted throughout the cells of the atria through gap junctions in that connect these cells

Question 2

PR segment

Answer 2

Depolarization of the AV node. I.e. When current is passing through the AV node. It’s a flat line because the wave is not strong enough to be recorded on the voltmeter.

Question 3

PR Interval

Answer 3

Wave goes over the atrium and through the AV node and ends just before it activates the ventricles to depolarize

Question 4

Q Wave

Answer 4

Ventricular Septal Depolarization

Question 5

R Wave

Answer 5

Resultant or major ventricular muscle depolarization. The resultant vector is directed downward and leftward.

Question 6

S Wave

Answer 6

Basal Ventricular depolarization, i.e. depolarization of the base of the ventricles. Note the apex of the heart is the L. pointed end. The base of the ventricles connects to the atria

Question 7

ST Segment

Answer 7

During the ST segment, all the ventricular myocardium is depolarized. All have positive charges. So there is nothing potential difference to be recorded by the voltmeter (ECG machine). So you have a flat line

Question 8

T Wave

Answer 8

Represents ventricular repolarization

Question 9

QT Interval

Answer 9

Important because it captures the beginning of ventricular depolarization through the plateau phase to the ventricular repolarization. It covers the entire ventricular activity. During this time, the action potential was generated and terminated in the ventricular tissue

Question 10

QRS Complex

Answer 10

The start of ventricular systole and that goes until the end of the T wave. Ventricular diastole starts when the T wave ends.

Question 11

U Wave

Answer 11

Sometimes the electrical activity of the ventricular papillary muscle is out of phase with the rest of the ventricles and will record as a “U” wave that shows after the T wave