Cardiac Output

Question 1

amount of stretch on the myocardial cells in ventricles by the volume of blood just prior to contraction; proportional to LVEDV/P

Answer 1

Preload

Question 2

Increasing the preload will do what to the stroke volume

Answer 2

Increase

Question 3

Increased stretch of the muscle fibers due to increased preload does what to the contractile force

Answer 3

Increase contractile force by allowing more cross-bridging (stretching causes greater sarcomere length leading to more cross-bridge formation).

Question 4

How can a arterial vasodilator increase cardiac output?

Answer 4

Decreased afterload (less pressure to push against)

Question 5

Decreased vascular compliance leads to what in afterload

Answer 5

increased

Question 6

Preload and afterload are both easily definable by single points on the LV pressure vs. volume graph (True or False)

Answer 6

False (Preload is, but afterload is not)

Question 7

Increasing afterload does what to the velocity of myofibril shortening

Answer 7

Decreases (struggles to push out the blood)

Question 8

measure of strength generated by myocardial contraction during systole; proportional to how many actin-myosin crossbridges are made; independent of preload and afterload

Answer 8

Contractility

Question 9

contractility is (dependent/independent) of preload and afterload

Answer 9

Independent

Question 10

Determinants of contractility

Answer 10

Increased intracellular calcium
Myosin ATPase activity
ATP levels
Number of sarcomeres

Question 11

When increase in HR actually decreases cardiac output due to decreased filling time (what bpm?)

Answer 11

> 180 bpm

Question 12

How does increased HR increase contractility?

Answer 12

More Ca available

Question 13

ventricular wall tension during contraction; the pressure within the arteries & arterioles that the ventricles must overcome before pushing blood through the aortic valve.

Answer 13

afterload

Question 14

Preload is determined by ______

Answer 14

LVEDV or LVEDP

Question 15

Where do you find preload in the PV Loop graph?

Answer 15

Preload is the pressure at the maximum volume in the passive component of the PV Loop.

Question 16

Where do you find preload in the pressure-time graph?

Answer 16

When the mitral valve closes just before isovolumetric contraction occurs

Question 17

Where do you find preload in the ECG?

Answer 17

Peak of R wave

Question 18

Increasing end diastolic volume or end diastolic pressure will lead to increased

Answer 18

stroke volume

Question 19

What is the formula for LaPlace?

Answer 19

T=Pr/2u

• know what they represent

Question 20

Since preload is the ventricular wall tension (wall stress), it is a major determinant of

Answer 20

oxygen demand

Question 21

Increasing preload will increase

Answer 21

myocardial oxygen demand

Question 22

What main factor regulates preload?

Answer 22

Central venous pressure (pressure in the veins of systemic circulation)

Question 23

CVP is equal to

Answer 23

right atrium pressure (since no valves are involved when blood returns to the heart from the systemic circulation)

Question 24

Increased CVP or right atrium pressure increases

Answer 24

preload

Question 25

What 3 factors regulate CVP?

Answer 25

1. venous tone
2. blood volume
3. body position

Question 26

How is CVP regulated by venous tone?

Answer 26

Sympathetic activity increases tension in walls of veins (and arteries). This increases central venous pressure and pushes blood into the right atrium, increasing preload.

Question 27

How is CVP regulated by blood volume?

Answer 27

The majority of our blood is in the veins/venules. Increased blood volume would lead to increased preload.

Question 28

How is CVP regulated by body position?

Answer 28

Body position changes central venous pressure. If we’re standing, gravity causes decrease in central venous pressure. If we’re lying down, gravity evenly hits CVP throughout body and doesn’t cause an impact

Question 29

Increased arteriolar dilation leads to

Answer 29

increased CVP

Question 30

any change in CVP, pulmonary, or atrial pressures will change

Answer 30

preload