Cardiac cycle

Question 1

What are the phases of the cardiac cycle

Answer 1

1a. Rapid ventricular filling
1b. Diastasis - ventricular filling has slowed
1c. Atrial systole
2. Isovolumetric contractions- ventricles contract with no volume change as all valves are closed
3. Pressure in ventricles exceeds that of the aorta/pulmonary arteries so semilunar valves open and blood is ejected from the ventricles
4. Isometric relaxation - Ventricles relax with no change in volume as all valves are closed

Question 2

What does the P wave show

Answer 2

The start of atrial muscle contraction

Question 3

How much blood does atrial contraction add to the ventricles

Answer 3

Only a small amount - rapid filling stage has already taken place - Causes an increase in both atrial and ventricular pressures

Question 4

What Occurs during the QRS complex

Answer 4

Ventricular depolarization

Question 5

Why does pressure rise in the atria during ventricular depolarisation

Answer 5

Because mitral or tricuspid valve both push back into the atria due to the increased ventricular pressure

Question 6

What is sound S1 produced by on the echocardiogram

Answer 6

The closing of the mitral and tricuspid valves

Question 7

Does ventricular volume after systole drop to 0

Answer 7

No - end systolic blood volume remains

Question 8

What increase occurs in the rate of flow through the aorta after ventricular systole

Answer 8

0-5m/s very rapidly - Rate then falls and even drops below 0 - retrograde flow - this blood goes into the coronary sinus

Question 9

How is the S2 sound generated

Answer 9

Through the closure of the Aortic and pulmonary valves

Question 10

What does the A wave for the jugular pulse reflect?

Answer 10

Atrial contraction

Question 11

What does the jugular venous pressure mimic

Answer 11

Atrial pressure

Question 12

What does the C wave reflect

Answer 12

Bulging of the bicuspid or tricuspid valve back up into the atria during ventricular systole

Question 13

What does the X descent reflect

Answer 13

As the heart ejects blood is is laterally and caudally displaced - this stretches the veins attached to it and stretches them; increasing their volume and causing their pressure to fall

Question 14

Why does the right atria contract before the left?

Answer 14

Because the SAN is found on the right atrial wall, so their muscles are depolarised first

Question 15

Why does the left ventricle contract before the right?

Answer 15

Due to the anatomical distribution of the Purkinje fibres and Bundle of His

Question 16

Why is ejection from the right ventricle before that of the left?

Answer 16

Because pulmonary artery pressure is lower than that of the aorta so less work is needed to increase the ventricular pressure above that of the pulmonary artery .