14: Regulation of cardiac output Flashcards

1
Q

Cardiac output equation

A

CO= SVxHR

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2
Q

Cardiac output

A

Varies with O2 demands

Same as flow

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3
Q

Stroke volume

A

SV= end diastolic volume - end systolic volume

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4
Q

Main regulator of heart rate

A

ratio of parasym to symp inputs

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5
Q

Chronotropic

A

Heart rate

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6
Q

What increases chronotropic effects

A

Norepinephrine binding to B-1 androgenic receptors in SA

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7
Q

What decreases choronotropic effects

A

ACh binding to muscarinic receptors on pacemaker cells

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8
Q

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

A

Stroke volume decreases

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9
Q

Lusitropic effects

A

Increase and decrease rate of relaxation

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10
Q

What is the cause of positive Lusitropic effect

A

better cross bridge formation for Ca

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11
Q

Inotropic changes

A

Changes in contractility

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12
Q

intrinsic regulation of inotropic effects

A

mechanical properties of cardiac muscle

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13
Q

extrinsic regulation of inotropic effects

A

sympathetic innervation
hormonal
blood gas
pH

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14
Q

Active tension of sarcomeres is dependent on

A

Starting length of sarcomeres at time of activation

Actin-myosin overlap

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15
Q

Total tension =

A

Passive tension + active tension

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16
Q

Isometric

A

No blood movement

17
Q

Isotonic

A

blood movement

18
Q

What determines if a stretch will be active or passive

A

External constraints

19
Q

What are examples of external constraints in the heart

A

End dyistolic volume

Aortic pressure

20
Q

Preload

A

Stretch on the cardiac muscle that occurs during the relaxed state

21
Q

End diastolic volme

A

Volume load during diastole

22
Q

What does preload determine

A

the force generated y the cardiac muscle for the subsequent contraction

23
Q

Frank-Starling mechanism

A

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

24
Q

Isotonic contraction phase

A

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

25
What force does the ventricles need to overcome during isontonic contraction
Aortic pressure
26
What is the end systolic volume dependent on
afterload and contractility
27
What does an increase in aortic pressure do to stroke volume
Decrease stroke volume
28
Contractility
performance of the heart at a give preload and afterload
29
What determines contractililty
Changes in intracellular Ca and a rate of contractile protein interaction
30
How is cardiac muscle contractility gaded
Extrinsic mechanisms
31
4 hormonal influences on myocardial function
1. Epinephrine 2. Thyroid hormone 3. Increases in CO2 4. Myocardial ischemia