Regulation of Cardiac Output

Question 1

Define the Frank-Starling mechanism?

Answer 1

the intrinsic ability of the heart to adapt to changing volumes of blood

Question 2

What is the proposed mechanism for the Frank-Starling mechanism?

Answer 2

more stretch –> optimal sarcomere length –> increased contraction

Question 3

What does a ventricular function curve plot?

Answer 3

Work (g*m) vs. Right Atrial Pressure (mmHg)

Question 4

What term equals afterload.

Answer 4

TPR, but is best reflected through MAP

Question 5

What determines afterload?

Answer 5

arteriolar tone

Question 6

What is the effect of increased afterload?

Answer 6

1) increased TPR/MAP –> increased LVESP
2) decreased SV
3) Work (area) is constant, so CO must decrease

Question 7

What range of blood pressure yields decompensated heart failure?

Answer 7

200+ mmHg

Question 8

How does cardiac compensation occur, and in response to what?

Answer 8

response to decreased CO

1) HR
2) contractility
3) TPR

Question 9

For an given preload, the heart pumps more blood. How?

Answer 9

increased HR, increased contractility

via SYMPATHETIC drive

Question 10

For a given preload, the heart pumps less blood. How?

Answer 10

decreased contractility & decreased HR

need BOTH pns & sns!

Question 11

What is the effect of increased contractility related to the PV loop?

Answer 11

1) decreased LVESV
2) preload is constant, so SV increases
- - slight increase in BP, increased demand for venous return

Question 12

What is the effect of decreased cardiac compliance?

Answer 12

for any level of blood, pressure is increased

1) LVEDV (preload) decreases since AV valve closes @ same pressure
2) all pressures are constant
3) decreased SV!

Question 13

What causes decreased cardiac compliance?

Answer 13

1) aging

2) hypertrophy