Cardiac physio.L5. Cardiac output

Question 1

what is the pressure range in the aorta?

Answer 1

80-120 mmHg

Question 2

What is the pressure range in the left atria?

Answer 2

0-20

Question 3

What is the pressure range in the Left Ventricle?

Answer 3

0-120 mmHg

Question 4

What if the pressure range in pulmonary trunk?

Answer 4

8-27 mmHg

Question 5

What causes the first heart sound?

Answer 5

The first heart sound (S1) represents closure of the atrioventricular (mitral and tricuspid) valves as the ventricular pressures exceed atrial pressures at the beginning of systole. S1 is normally a single sound because mitral and tricuspid valve closure occurs almost simultaneously.

NOT the closing of the valves per se, but the turbulence of blood created

Question 6

What causes the 2nd heart sound?

Answer 6

The second heart sound (S2) represents closure of the semilunar (aortic and pulmonary) valves (point d). S2 is normally split because the aortic valve (A2) closes before the pulmonary valve (P2).
Happens when the pressure in the ventricle drops and the blood tries to move back from the aorta and pulmonary trunk slamming the valve shut.

Question 7

What is the normal stroke volume?

Answer 7

70 ml

Question 8

what is the equation for cardiac output?

Answer 8

HR x SV

Question 9

What is a normal cardiac output?

Answer 9

5 L/min

Question 10

Normal HR and SV

Answer 10

HR: 60-100 bpm
SV: 50-100 bpm

Question 11

How is Stroke Volume calculated?

Answer 11

SV= End Diastolic Volume( 120-140 ml) - End Systolic Volume( 50-70 ml)

Question 12

What is a good ejection fraction?

Answer 12

50% of the blood ejected from the ventricle

Question 13

What determines SV?

Answer 13

Preload
Contractility
Afterload

Question 14

What is preload?

Answer 14

“the force that stretches the cardiac muscle prior to contraction”
the measure of filling of the heart
More volume= more pressure when ventricle contracts

Question 15

What is the relationship between venous return and SV?

Answer 15

Increasing Venous return to the heart increases Stroke Volume

Directly proportional

Question 16

What factors affect End Diastolic Volume?

Answer 16

• Venous return
• Blood volume
• Filling time
• Respiratory pump
• Compliance eg MI damage

Question 17

How is a change in venous return achieved?

Answer 17

• Change in blood volume( dehydration)-> lower blood volume-> lower venous return
• Smooth muscle contraction

Question 18

How can filling time be changed?

Answer 18

increasing HR decreases filling time

-puts a physiological filling on how high HR can get

Question 19

How can respiratory pump affect End Diastolic Volume?

Answer 19

-Heart is exposed to -ve pressure. Breathing in deeper can increase venous return

Question 20

Frank-Starling Law of the Heart

Answer 20

“the stroke volume of the left ventricle will increase as volume increases due to the myocyte stretch causing a more forceful systolic contraction”

Question 21

What is contractility?

Answer 21

“The performance of the heart at a given preload and afterload. Inotropy”
Heart can work harder at the same level of filling if it receives external stimuli”

Increasing contractility decreases ESV and increase SV( coffee can increase contractility)

Heart problems can decrease contractility and in turn decrease SV

Question 22

What is Afterload and how does it affect the SV?

Answer 22

“the amount of pressure that the heart needs to exert to eject the blood during ventricular contraction”

Increasing afterload increases ESV, and decreases SV

e.g high blood pressure, valve pathologies, aortic plaques

Question 23

What state is the mitral valve in the beginning of EDV?

Answer 23

Closes

Question 24

What happens to the aortic valve at the ESV?

Answer 24

Begins to close

Question 25

What part of the pressure volume loop represents mitral valve closing?

Answer 25

B(EDV)