ECG Basics and Cardiac Cycle

Question 1

P wave

Answer 1

SA node causes atria to depolarize from right to left.

Question 2

QRS complex

Answer 2

Ventricular depolarization from right to left, apex to base and interior to exterior.

Question 3

ST segment

Answer 3

Action potential phase 2 delays repolarization of ventricles.

Question 4

T wave

Answer 4

Ventriclar repolarization from left to right.

Question 5

PR interval

Answer 5

Beginning of P wave until beginning of QR.

Question 6

QT interval

Answer 6

From beginning of QR to the end of T wave.

Question 7

PR segment

Answer 7

End of P wave to the beginning of QRS.

Question 8

ST segment

Answer 8

End of QRS to the beginning of T wave.

Question 9

Aortic pressures

Answer 9

120/80

Question 10

Ventricular pressures

Answer 10

120/0

Question 11

Ventricular volumes

Answer 11

120 mL to 50 mL

Question 12

Atrial pressures

Answer 12

15/4

Question 13

Atrial systole

Answer 13

Arial pressure increases as the atria contract. Ventricular pressure mildly increases as blood is pushed from atria to the ventricles.

Question 14

Ventricular systole

Answer 14

After the atria contract and begin to relax, the ventricles start to contract. The ventricular pressure increases rapidly. Once the ventricular pressure exceeds atrial pressure, the AV valves close and prevent back flow. There is mild increase in atrial pressure as venous blood returns.

Question 15

What causes the ejection of blood from the ventricles?

Answer 15

When the pressure in the ventricles exceeds the pressure in the pulmonary artery and the aorta.

Question 16

Isovolumetric contraction

Answer 16

Occurs in ventricular systole.

Ventricular volume remains constant while the pressure increases rapidly.

Question 17

What pressure does the L and R ventricles have to reach before the AV valves open?

Answer 17

Must exceed the diastolic pressure on each side to open the valve.

Question 18

Once the pressure in the aorta exceeds ventricular pressure, what happens to volume?

Answer 18

Valves open and volume decreases.

Question 19

Ventricular diastole

Answer 19

Pressure in the ventricle drops below arterial pressure and the valves close. Aortic and ventricular pressures diverge rapidly.
When the atrial pressure exceeds ventricular pressure, the AV valves will open and blood will passively move into the ventricles.

Question 20

Dicrotic notch is produced by:

Answer 20

Closing of the aortic valve.

Question 21

Isovolumetric relaxation

Answer 21

Occurs in ventricular diastole.

No blood enters or leaves the ventricle while it is relaxing because the AV and aortic valves are closed.

Question 22

Why does blood flow rapidly into ventricles?

Answer 22

Because the ventricular pressure and volume are both very low.

Question 23

Peripheral runoff

Answer 23

Blood leaving the aorta and flowing into the smaller vessels in the periphery during ventricular diastole.

Question 24

a wave

Answer 24

Venous pressure created by atrial contraction.

The pressure is reflected backwards.

Question 25

c wave

Answer 25

Venous pressure wave created by the period of isovolumetric contraction of the ventricles.

Question 26

v wave

Answer 26

Venous pressure wave created as blood returns back to the heart but cannot enter the ventricle.