Physiology of the cardiac cycle -february 17

Question 1

How valves work

Answer 1

• one way valves

- open only when pressure upstream exceeds pressure downstream

Question 2

Heart sounds

a) how are they produced
b) heart sounds and what event they corresponds to

Answer 2

-opening of valve is silent (normally)
-closing of valves produces a sound (due to vibrations from abrupt changes in flow)
AV closure = S1
Semilunar closure = S2

Question 3

When does the ticupid valve open

Answer 3

RAP > RVP

Question 4

When does the pulmonary valve open

Answer 4

RVP > Pulm art press

Question 5

When does the mitral valve open

Answer 5

LAP> LVP

Question 6

When does aortic valve open

Answer 6

LVP > Aortic artery press

Question 7

Diastole-what part of cycle (2 events)

Answer 7

-ventricular relaxation and filling

Question 8

Systole -what part of the cycle (2 events)

Answer 8

-ventricular contraction and ejection

Question 9

Atrial pressure waves

Answer 9

1) a wave
2) c wave
3) v wave

Question 10

a wave

Answer 10

-coincides with atrial contraction which elevates LAP pressure

Question 11

c wave

Answer 11

-coincides with ventricular contraction, bulging mitral valve leaflets into the left atrium and therefore slightly increasing LAP

Question 12

v wave

Answer 12

• coincides with atrial filling (from blood returning from lungs)
• relaxed atrium is very compliant and can hold consideral volume at relatively low pressure

Question 13

Cause of First heart sound (S1)

Answer 13

• occurs in conjunction with closure atrioventricular valves
• sound caused by vibration of valves and walls of heart that occur as a result of their elastic properties when the flow through the valves is suddenly stoped

Question 14

Where can best hear S1

Answer 14

Near the apex of the heart

Question 15

Cause of 2nd heart sound

Answer 15

-same reason as 1st but occuring in conjunction with closure of the pulmonic and aortic valves

Question 16

Where can best hear S2

Answer 16

• pulmonic closure is best heard in the 2nd/3rd intercostal space left sternal border
• aortic closure is best heard in the 2nd/3rd intercostal space right sternal border

Question 17

Physiological splitting

Answer 17

• inspiration S2 heard as 2 sounds

- expiration S2 heard as 1 sound

Question 18

Mechanism of physiological splitting

Answer 18

• during inspiration negative intrathoracic pressure facilitates enhanced venous return to right heart = delayed pulmonic valve closure
• at same time reduced venous return to left heart (due to increased pulmonary capacitance) means the aortic valve closes earlier
• draws to sounds apart

Question 19

S3

a) when in the cardiac cycle does it occur
b) what does it indicate - in children and adults?

Answer 19

• occurs in early diastole during rapid filling and expansion of the ventricle
• heard normally in children
• in adults indicates volume overload due to congestive heart failure

Question 20

S4

a) when does it occur
b) what does it indicate?

Answer 20

• can occur during atrial systole (late ventricular diastole)
• due to atria vigorously contracting against a stiffened ventricle
• can indicate presence of cardiac disease (ventricular hypertrophy)

Question 21

Gallop

Answer 21

S1 and S2 + S3 and/or S4

Question 22

Cardiac murmur - cause

Answer 22

-sound generated by turbulent flow through the heart

Question 23

Causes of turbulent flow in the heart (5)

Answer 23

1. Flow across a partial obstruction (aortic valve stenosis)
2. Increased/disturbed flow through normal structures (aortic systolic murmur in anemia -decreased viscosity and increased velocity)
3. Ejection into dilated vessel/chamber (aneurismal dilation of the aorta)
4. Regurgitant flow across an incompetent valve (mitral regurgitation)
5. Abnormal shunting from high to low pressure chamber (ventricular septal defect)