Heart Pump

Question 1

What is ejection fraction and how is it calculated?

Answer 1

measure of volume of blood the left heart pumps after each contraction
- EF= SV/EDV
where SV= EDV-ESV

Question 2

How does one calculate pulse pressure?

Answer 2

Systolic pressure minus the diastolic pressure.

- 120/80 gives us 120-80 and a pulse pressure of 40mmHg

Question 3

Which valves are closing creating the “lub” of the heart sounds? When does this happen?

Answer 3

AV valves (mitral and tricuspid)
-end diastole

Question 4

Which valves are closing creating the “dub” of the heart sounds? When does this happen?

Answer 4

Semilunar valves (aortic and pulmonary)
- End of systole

Question 5

What is the equation for Cardiac output?

Answer 5

Co= HR*SV

• thus call changes in CO must come from SV or HR
• parasympathetic and sympathetics have immediate effects (within 1 beat)
• Phase 4 for HR is affected.

Question 6

What is preload? and what are its surrogates?

Answer 6

End diastolic Pressure/ Volume

- EDV and arterial pressure

Question 7

An increase in preload will do what 2 things?

Answer 7

1. increase initial muscle fiber length and thus increase extent of shortening
2. Increase end diastolic volume and stroke volume

Question 8

What is after load? and what is it surrogate?

Answer 8

Active tension placed on cardiac muscle cells during contraction

• mean arterial pressure (MAP= DP+1/3PP)
• or MAP= 2/3 DP + 1/3 SP
• because heart is in diastole 2/3 of the time

Question 9

What will the affects of after load be?

Answer 9

1. Negative effects on cell shortening
2. Normal: after load held constant and thus minimal effects on SV
3. Leads to decrease of SV from HTN/Aortic valve obstruction

Question 10

What is the relationship between fiber shortening and contractibility?

Answer 10

An increase in cell shortening leads to an increase there of contractibility

Question 11

How does SNS or NE lead to increase contractibility?

Answer 11

Increase fiber shortening

- upward and left shift of length-tension curve

Question 12

What does SNS or NE do the SV?

Answer 12

Increases it because it increases Contractibility through more shortening which is related to decreased ESV!

Question 13

How does innervation of SNS effect the CO, HR, SV and pressure?

Answer 13

Increase the CO, HR and SV

While pressure remains the same

Question 14

What receptor does NE bind to on the heart?

Answer 14

Beta- 1 Andrenergic

Question 15

What positive effects does NE have?

Answer 15

1. Chronotropic
2. Dromotropic
3. Inotropic
4. Lusitropic

Question 16

What does positive chronotropic effect mean?

Answer 16

Activated funny-current in SA node via increase of Na and Ca Permeablity while keeping K about the same. Thus increases likelihood of AP

Question 17

What is a positive dromotropic effect?

Answer 17

Increase AP conduction (mainly of AV node)

- increases Gap Junctions conductivity

Question 18

What is a positive inotropic effect?

Answer 18

Increase in cardiac contractibility.

- increase in Ca current and Ca release from SR

Question 19

What is a positive lusitropic effect?

Answer 19

increase cardiac relaxation

• increase CA uptake by SR
• basically increase turnover for next contraction to compensate for increase HR

Question 20

What is another way to have a positive lusitropic effect?

Answer 20

decrease AP duration by inducing early activation of K current for faster repolarization

Question 21

What is the primary source of fuel for the heart in adults, children and CHF patients?

Answer 21

ATP 60-90%

1. Fatty acids
2. Glucose and lactate
3. Glucose

Question 22

The heart relies on what sort of respiration?

Answer 22

Aerobic meaning loads of mitochondria

- only anaerobic can make enough energy to serve the heart for a few minutes

Question 23

What is the percent of ATP used by basal metabolism and muscle contraction?

Answer 23

25 and 75% respectively

Question 24

What is so costly of the muscle contraction?

Answer 24

isovolumetric contraction 50%

- heavily depends on afterload

Question 25

What would cause your heart to expend more energy by an increase in afterload?

Answer 25

HTN and Aortic valve obstruction