3- Mechanical Propeties 2

Question 1

What is the EDV, ESV and SV

Answer 1

END DIASTOLIC VOLUME (EDV) = the volume in the ventricles just before
END SYSTOLIC VOLUME (ESV) = the volume in the ventricles after the ventricle has completely contracted and expelled as much blood as it is going to
STROKE VOLUME (SV) = EDV - ESV

Question 2

What is the ejection fraction

Answer 2

EJECTION FRACTION (EF) = the proportion of the end diastolic volume that is pumped out of the heart (Ejection Fraction = SV/EDV)

Question 3

What are the 7 steps of the Cardiac cycle

Answer 3

1. Atrial Systole
2. Isovolumic Contraction
3. Rapid Ejection
4. Reduced Ejection
5. Isovolumic Relaxation
6. Rapid Ventricular Filling
7. Reduced Ventricular Filling

Question 4

Describe atrial systole

Answer 4

Depolarisation stimulated by SAN
P wave on ECG
Contraction tops off volume in ventricle

Question 5

Isovolumetric contraction

Answer 5

AV valves closed (lub)
QRS wave on ECG
Contraction of ventricles with no volume change
Isometric contraction

Question 6

Ventricular ejection

Answer 6

SL valves open

V. Pressure > aortic/ pulmonary pressure

Question 7

Reduced ejection

Answer 7

Volume of blood in V. Decreases so pressure decreases
SL begin to close
T wave due to repolarisation

Question 8

Isovolumetric relaxation

Answer 8

SL closed (dub)
Atria have filled with blood but AV valves shut

Question 9

Rapid ventricular filling

Answer 9

AV valves open, blood flows into ventricles

If there is turbulent ventricular filling, there will be a 3rd sound(ventricular gallop)

Question 10

Reduced ventricular filling

Answer 10

Ventricular volume increases more slowly

Question 11

What is the pressure in the systemic and pulmonary systems

Answer 11

120/80. 25/5mmHG

Question 12

What can cause sound 4

Answer 12

During atrial systole
S4 is usually caused by valve incompetency (valves don't shut properly making the blood flow become turbulent)
Pulmonary Embolism 
Congestive Heart Failure 
Tricuspid Incompetence

Question 13

What causes the jugular pulse, c wave and v wave

Answer 13

• JUGULAR PULSE - you may feel a small pulse in the jugular at this time due to the atrial contraction pushing some blood back up the jugular vein during atrial systole
The ‘c wave’ seen in the atrial pressure is caused by the right ventricular
contraction pushing the tricuspid valve into the atrium and creating a small wave into the jugular vein during ventricular ejection
‘v wave’ in the atrial pressure is caused by blood pushing the tricuspid valve and giving a second jugular pulse during isovolumetric relaxation

Question 14

What is the dichrotic notch

Answer 14

DICHROTIC NOTCH - small, sharp increase in aortic pressure due to the rebound pressure against the aortic valve as the distended aortic wall relaxes during isovolumetric relaxation

Question 15

How is pressure in the right side different to left side of heart

Answer 15

Pressure is less in the right side, but same stroke volume

Question 16

Describe the pressure volume loop

Answer 16

• You plot VENTRICULAR PRESSURE against VENTRICULAR VOLUME
• Point 1 = End Diastolic Volume (EDV) - the ventricle has a large volume but hasn’t generated any pressure yet
• Point 2 = Isovolumic Contraction - the volume in the ventricle hasn’t changed but there is a large increase in pressure
At this point, the ventricular pressure has got to the same point as the
aortic pressure (afterload) and is just about to overcome it
• Between Point 2 and Point 3 = the ventricle starts to expel blood so the
volume of blood in the ventricle fall and the ventricular pressure rises then falls
• This ends on Point 3 which is the End Systolic Volume (ESV)
• THE DIFFERENCE BETWEEN POINT 3 and POINT 2 IS THE STROKE VOLUME
• Pressure falls in the ventricles due to Isovolumic Relaxation but the volume stays the same so there is a straight line downwards between Point 3 and Point 4

Question 17

What determines preload and afterload

Answer 17

Volume of blood in ventricles during diastole

Pressure in aortic and pulmonary artery

Question 18

Considering the Frank-Starling Relationship: what does Increasing preload do

Answer 18

Increases stroke volume: Point 1 and 2 move further to the right because there is more volume returning to the heart and hence the preload increases and End Diastolic Volume increases
The increase in stroke volume is shown by an increase in the distance between point 3 and point 2

Question 19

Considering the Frank-Starling Relationship: Increasing afterload

Answer 19

Decreases stroke volume

Point 2 moves up, so point 3 and 4 move right, so

Question 20

Name 3 factors affecting stroke volume

Answer 20

Preload
Afterload
Comtractility

Question 21

What is cardiac contractility

Answer 21

Definition: Contractile capability (or strength of contraction) of the heart
• Simple measure of cardiac contractility is the EJECTION FRACTION
• Contractility can be increased by sympathetic stimulation

Question 22

How does exercise affect contractility

Answer 22

Changes in peripheral circulation (e.g.
venoconstriction and muscle pump) means that more blood is returned to the heart and so End Diastolic Volume INCREASES
• So the increase in End Diastolic Volume (EDV) means that point 1 and 2 are pushed further right
• And the increase in contractility means that point 3 and 4 are pushed further to the left
• Thus there is an INCREASE in stroke volume