4. Muscle Physics and Heart as a Pump

Question 1

What is the average resting CO?

Answer 1

5 L/min

Question 2

What is the stroke volume?

Answer 2

the amount of blood pumped per beat

Question 3

What is CO?

Answer 3

cardiac output: heart rate x stroke volume (the volume of blood pumped per minute by the heart)

Question 4

How is CO controlled?

Answer 4

1. heart rate (SA node, ANS and humoral agents)

2. stroke volume (preload, afterload, strength of contraction)

Question 5

What sets the heart rate?

Answer 5

pacemaker cells in the SA node

Question 6

What is the preload?

Answer 6

the venous return

Question 7

What is afterload?

Answer 7

resistance to flow (aortic pressure)

Question 8

What 2 things change the strength of contraction??

Answer 8

1. length dependent regulation (Frank-Starling Law)

2. length independent regulation (via SNS)

Question 9

What is the first phase of the cardiac cycle?

Answer 9

the filling phase

Question 10

What occurs during the filling phase?

Answer 10

the mitral valve is open; volume high and pressure low

Question 11

What is the second phase of the cardiac cycle?

Answer 11

the isovolumetric contraction phase

Question 12

What happens during the isovolumetric contraction phase?

Answer 12

the aortic valve is closed; volume and pressure greatly increase, closing the mitral valve

Question 13

What is the third phase in the cardiac cycle?

Answer 13

the ejection phase

Question 14

What happens during the ejection phase?

Answer 14

blood leaves the ventricle- pressure is highest but volume reaches lowest

Question 15

What is the fourth phase in the cardiac cycle?

Answer 15

isovolumetric relaxation phase

Question 16

What happens during the isovolumetric relaxation phase?

Answer 16

the aortic valve closes; mitral valve closed

Question 17

When does the mitral valve open?

Answer 17

at the beginning of the filling phase

Question 18

What is the end diastolic curve?

Answer 18

the volumes and corresponding pressures during diastole

Question 19

What does EDPVR stand for?

Answer 19

end diastolic pressure volume relationship

Question 20

The EDPVR represents the _____ on the left ventricle.

Answer 20

preload

Question 21

The EDPVR represents the preload on the _____.

Answer 21

left ventricle

Question 22

What is the significance of Starling’s Law of the Heart?

Answer 22

what comes into the heart must be pumped out

Question 23

Name various sources of resistance to filling.

Answer 23

1. R atrial pressure
2. AV valve stenosis
3. ventricular compliance

Question 24

What are the factors that affect preload?

Answer 24

1. blood volume
2. filling pressure and time
3. resistance to filling

Question 25

What does SVPR stand for?

Answer 25

Systolic pressure-volume relationship

Question 26

Which is steeper- the SVPR or the EDPVR?

Answer 26

SVPR by a lot

Question 27

What is the SVPR?

Answer 27

Maximum pressure that can be developed by the ventricle for a given set of circumstances

Question 28

Violation of Starling’s law corresponds to?

Answer 28

heart failure

Question 29

The heart responds to an increase in EDV by ____.

Answer 29

increasing the force of contraction

Question 30

A healthy heart always functions on the ____ limb of the ventricular function curve.

Answer 30

ascending

Question 31

Cardiac output MUST equal _____ and cardiac output from left and right ventricles MUST match.

Answer 31

venous return

Question 32

What is the ESV?

Answer 32

end systolic volume- not zero! usually around 50 mL