Cardiac Cycle

Question 1

Describe the difference in pressure generated by the left and right heart

Answer 1

Pressure generated by the right heart is much lower than the left because less pressure is required to pump blood through the pulmonary circulation than the systemic circulation

Question 2

What are the first and second heart sounds?

Answer 2

First heart sound - closure of the AV valves at the onset of systole

Second - Closure of the semilunar valves at the end of systole

Question 3

What events are associated with ventricular systole?

Answer 3

Isovolumetric contraction (2)

Rapid ejection (3)

Reduced ejection (4)

Question 4

What events are associated with ventricular diastole?

Answer 4

Isovolumetric relaxation (5)

Rapid ventricular filling (6)

Reduced ventricular filling (diastasis) (7)

Atrial systole (1)

Question 5

What causes the P wave of the ECG?

Answer 5

Atrial depolarization

Question 6

What is the difference between at rest and during exercise ventricular filling?

Answer 6

Atrial systole accounts for only a small fraction of V-filling at rest

During exercise and other conditions of increased HR, a greater fraction of V-filling is due to atrial systole because of less time available for passive filling

Question 7

What generates the QRS complex on an ECG?

Answer 7

Spread of an AP through the ventricles

Indicates the initiation of ventricular contraction

Question 8

What is the isovolumetric contraction (2)?

Answer 8

The interval between AV valve closure and semilunar valve opening

Ventricles contract with a fixed volume because no blood is entering or leaving

Question 9

What happens during rapid ejection?

Answer 9

Ventricular pressure continues to increase

Aortic and Pulmonary artery pressures increase

Blood flow into the aorta and pulmonary artery peaks

Ventricular volume decreases

Question 10

What is the T wave of the ECG?

Answer 10

Ventricular repolarization

Associated with phase 4 of the cardiac cycle

Question 11

Describe the reduced ejection phase

Answer 11

Ventricles start to relax and the ejection of blood slows

Accounts for about 30% of stroke volume

Aortic pressure declines

Question 12

What is the dicrotic notch?

Answer 12

Slight upward deflection in the pressure tracing that is associated with the closure of the semilunar valves

Signals the start of diastole

Question 13

What is isovolumetric relaxtion?

Answer 13

Both sets of valves are closed and the ventricles continue to relax without being filled

Aortic pressure continues to decline gradually during this phase

Question 14

What is the end systolic volume?

Answer 14

Volume of blood remaining in the ventricles after ventricular contraction

Question 15

Describe the rapid filling phase (6)

Answer 15

Ventricular pressure falls below atrial pressure, allowing the AV valves to open

Filling is rapid because venous return has filled the atria prior to the opening of the AV vavles

Resistance to flow through the AV valves is low

Question 16

Why does the rate of passive filling slow and reach a plateua during diastasis?

Answer 16

Ventricles become less compliant as they fill

Question 17

What is the reason for physiological splitting of the second heart sound?

Answer 17

Aortic valve closure precedes pulmonary valve closure

These sounds are indistinguishable from each other during expiration, but separated during inspiration

Question 18

What is the third heart sound?

Answer 18

Occurs early in diastole and is caused by blood hitting the ventricles

Normal in a young person, but abnormal in adults over 40

Question 19

What is the fourth heart sound?

Answer 19

Contraction of the atria during late diastole

Commonly associated with resistance to filling and often a sign of diastolic hear failure

Question 20

What are heart murmurs and two common causes?

Answer 20

Sounds generated by turbulent blood flow

Stenosis - narrowing of the valve

Regurgitation - backward flow

Question 21

What is the a wave of the jugular pulse?

Answer 21

Upward deflection prodcued by right atrial contraction

Question 22

What is the x descent of the jugular pulse?

Answer 22

Downward component of the a wave associated with right atrial relaxation

Question 23

What is the c wave of the jugular pules?

Answer 23

Upward deflection that interrupts the x descent

Produced by bulging of the tricupsid valve into the right atrium

Question 24

What is the v wave of the jugular pulse?

Answer 24

Upward deflection caused by filling of the right atrium when the tricuspid valve is closed

Question 25

What is the y-descent of the jugular pulse?

Answer 25

Caused by rapid flow of blood into the right ventricle when the tricuspid valve opens