Heart Lecture 8: Cardiac Function

Question 1

Why is the shape of the ejection phase of the heart (PV loop) not flat?

Answer 1

because the afterload is not constant (blood flow into the aorta raises the afterload)

Question 2

What is the equation for ejection fraction?

Answer 2

(EDV-ESV)/EDV * 100

Question 3

What is the ejection fraction a clinical indicator of?

Answer 3

left ventricular contractility

Question 4

How does an increase in preload affect muscle fiber shortening?

Answer 4

increases it (makes it shorter)

Question 5

How does an increase in preload affect maximum tension development?

Answer 5

it doesn’t change

Question 6

How does an increase in preload affect the resting tension?

Answer 6

Increases resting tension

Question 7

How does an increase in preload affect the end diastolic pressure (the pressure on the ventricles after filling?)

Answer 7

increases it

Question 8

How does an increase in preload affect the stroke volume?

Answer 8

increases it

Question 9

Define end systolic volume

Answer 9

the volume left in the ventricles after contraction

Question 10

Define preload in terms of end diastolic and systolic volume

Answer 10

Preload is the difference between EDV and ESV