Control of Cardiac Output Flashcards

1
Q

What is afterload?

A

The load the heart must eject blood against

~aortic pressure

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2
Q

What is preload?

A

Amount the ventricles are stretched in diastole

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3
Q

What is total peripheral resistance?

A

Resistance to blood flow offered by all the systemic vasculature

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4
Q

What happens to pressure of a fluid in a tube when it encounters resistance?

A

Increases pressure before resistance

Decreases pressure after resistance

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5
Q

Effects of raising TPR with CO unchanged

A

Arterial pressure increases
Venous pressure falls

Vasoconstriction

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6
Q

Effects of lowering TPR with CO unchanged

A

Arterial pressure decreases
Venous pressure increases

Vasodilation

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7
Q

Effects of raising CO with TPR unchanged

A

Arterial pressure increases
Venous pressure decreases

HR increases
Blood taken from venous system

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8
Q

Effects of lowering CO with TPR unchanged

A

Arterial pressure decreases
Venous pressure increases

Causes congestion in veins

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9
Q

How do you calculate cardiac output?

A

Stroke volume x heart rate

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10
Q

How do you calculate stroke volume?

A

End diastolic volume - end systolic volume

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11
Q

What happens in ventricular filling?

A

Ventricle fills until intraventricular pressure = venous pressure

The higher the venous pressure, the more the heart fills

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12
Q

What is the ventricular compliance curve?

A

Relationship between ventricular pressure and ventricular volume

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13
Q

What increases ventricular compliance?

A

Heart is dilated

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14
Q

What decreases ventricular compliance?

A

Hypertrophy - thicker ventricle walls

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15
Q

What is the Frank-Starling law of the heart?

A

The more the heart fills, the harder it contracts

The harder the heart contracts, the bigger the stroke volume

An increase in venous pressure will fill the heart more

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16
Q

What is contractility?

A

The force of a contraction for a given fibre length

17
Q

What happens when you increase contractility?

A

Increase the force of contraction

18
Q

What increases contractility?

A

Sympathetic stimulation

Circulating adrenaline

19
Q

What decreases contractility?

A

Reduce sympathetic stimulation

Heart failure

20
Q

What factors determine cardiac output?

A

How much ventricles empty

  • end diastolic volume and contractility
  • aortic pressure

Stroke volume x heart rate

Decrease in arterial BP

  • reduce in parasympathetic activity
  • increase in sympathetic activty
  • increase contractility
21
Q

What is demand led pumping?

A
Body metabolism increases
TPR falls
Arterial pressure falls
Increase in venous pressure
Heart pumps more