14: Regulation of cardiac output

Question 1

Cardiac output equation

Answer 1

CO= SVxHR

Question 2

Cardiac output

Answer 2

Varies with O2 demands

Same as flow

Question 3

Stroke volume

Answer 3

SV= end diastolic volume - end systolic volume

Question 4

Main regulator of heart rate

Answer 4

ratio of parasym to symp inputs

Question 5

Chronotropic

Answer 5

Heart rate

Question 6

What increases chronotropic effects

Answer 6

Norepinephrine binding to B-1 androgenic receptors in SA

Question 7

What decreases choronotropic effects

Answer 7

ACh binding to muscarinic receptors on pacemaker cells

Question 8

Why does cardiac output not increase at a linear rate as heart rate increases

Answer 8

Stroke volume decreases

Question 9

Lusitropic effects

Answer 9

Increase and decrease rate of relaxation

Question 10

What is the cause of positive Lusitropic effect

Answer 10

better cross bridge formation for Ca

Question 11

Inotropic changes

Answer 11

Changes in contractility

Question 12

intrinsic regulation of inotropic effects

Answer 12

mechanical properties of cardiac muscle

Question 13

extrinsic regulation of inotropic effects

Answer 13

sympathetic innervation
hormonal
blood gas
pH

Question 14

Active tension of sarcomeres is dependent on

Answer 14

Starting length of sarcomeres at time of activation

Actin-myosin overlap

Question 15

Total tension =

Answer 15

Passive tension + active tension

Question 16

Isometric

Answer 16

No blood movement

Question 17

Isotonic

Answer 17

blood movement

Question 18

What determines if a stretch will be active or passive

Answer 18

External constraints

Question 19

What are examples of external constraints in the heart

Answer 19

End dyistolic volume

Aortic pressure

Question 20

Preload

Answer 20

Stretch on the cardiac muscle that occurs during the relaxed state

Question 21

End diastolic volme

Answer 21

Volume load during diastole

Question 22

What does preload determine

Answer 22

the force generated y the cardiac muscle for the subsequent contraction

Question 23

Frank-Starling mechanism

Answer 23

Stroke volume increases if the EDV increases and everything else is constant
Equalize outputs between right and left ventricles

Question 24

Isotonic contraction phase

Answer 24

Total muscle force exceeds the external load and muscle begins to shorten

Question 25

What force does the ventricles need to overcome during isontonic contraction

Answer 25

Aortic pressure

Question 26

What is the end systolic volume dependent on

Answer 26

afterload and contractility

Question 27

What does an increase in aortic pressure do to stroke volume

Answer 27

Decrease stroke volume

Question 28

Contractility

Answer 28

performance of the heart at a give preload and afterload

Question 29

What determines contractililty

Answer 29

Changes in intracellular Ca and a rate of contractile protein interaction

Question 30

How is cardiac muscle contractility gaded

Answer 30

Extrinsic mechanisms

Question 31

4 hormonal influences on myocardial function

Answer 31

1. Epinephrine
2. Thyroid hormone
3. Increases in CO2
4. Myocardial ischemia