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CAR > Cardiac Output > Flashcards

Cardiac Output Flashcards

1
Q

What is cardiac output

A

The amount of blood pumped out of the heart per minute

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2
Q

What two factors affect cardiac output

A

Stroke volume
Heart rate

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3
Q

What is the end diastolic volume

A

Blood in ventricle after filling

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4
Q

What is end systolic volume

A

Volume of blood after ventricle contracts

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5
Q

How do you work out stroke volume

A

End diastolic volume - end systolic volume

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6
Q

What two main factors determine end diastolic volume

A

End systolic volume (how much blood was there before filling)
Heart rate (sets time available for filling)

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7
Q

What is the frank starling mechanism

A

It’s the hearts physiological ability to change its contraction force and stroke volume in réponse to changes in venous return.

If end diastolic volume is increased (due to more blood flowing from the veins)
There is more preload (force stretching the cardiac muscle)
So force of contraction increases

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8
Q

What is contractility

A

the tension developed and velocity of shortening (i.e., the “strength” of contraction) of myocardial fibers at a given preload and afterload

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9
Q

When considering cardiac function, which index is more important for perfusion of peripheral tissues - cardiac output or blood pressure?

A

Cardiac output because blood pressure is influenced by cardiac output

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10
Q

How does contractility of the heart change during physical exercise? How is this brought about?

A

Exercise increases the sympathetic activity and reduces sympathetic activity, leading to increased contractility and increased stroke volume.

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11
Q

What happens to the heart rate after a major haemorrhage

A

Increases.

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12
Q

What happens to the venous return after a major haemorrhage?

A

Reduces

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13
Q

What happens to the total peripheral resistance after a major haemorrhage?

A

Increases

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14
Q

What is the equation involving blood pressure and cardiac output

A

CO = blood pressure x total peripheral resistance

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15
Q

What happens to the tissue fluid volume after a major haemorrhage

A

Decreases

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16
Q

What happens to urine output after a major haemorrhage

A

Decreases

17
Q

How are the changes in the body that occur after a major haemorrhage regulated?

A

Restore hydration (using IV fluids if necessary), open airways, use oxygenation and manage body temperature.

18
Q

What happens to cardiac output in heart failure?

A

During heart failure, the body does not receive enough blood and oxygen. So, the body’s hormone and nervous systems try to compensate for this by increasing blood pressure, holding on to sodium and water in the body, and increasing heart rate.
Cardiac output decreases, low stroke volume,

19
Q

What happens if stroke volume isn’t matched

A

Increase pressure on venous side
Leading to oedema

20
Q

What is preload

A

End diastolic volume
(Volume after filling)

21
Q

What is after load

A

Resistance to ventricular ejection

22
Q

What is preload dependant on

A

Venous return of blood
Will pump out same volume of blood that comes into heart

23
Q

What is the length tension relation ship

A

Increase preload
Increase exposure of myosin to actin (as sarcomere stretches)
Increase cross bridge formation
Increase force of contravtion

24
Q

What factors influence preload

A

Filling time of heart (slow HR means longer period of ventricular filling )
Venous return pressure difference between venous system and atrium)

25
Q

What does the skeletal muscle pump do to venous retun

A

Increase it
Contraction of skeletal muscle causes veins to be compressed
Blood forced to heart
Increased pre load

26
Q

What happens during inspiration to venous return

A

Diaphragm moves causally
Increases abdominal pressure
Thorax pressure reduces
So increases return of blood
Increases pre load

27
Q

What receptiors increase contractilité if heart

A

B1 adrenoreceptiors agonists

28
Q

What do positive inotropes do

A

Phosphorylates Ca2+ channels
Faster calcium re uptake
Increased contractility of heart

29
Q

What decreases ventricular contractility

A

M2 muscarinic receptors

30
Q

What does afterload

A

Creates the resistance against which the ventricle pumps

31
Q

What happens if you have more afteoq d

A

Reduced stroke volume
Heart has to work harder to maintain CO

32
Q

What happens if you have reduced aftoad

A

More blood can be ejected

33
Q

What is the equation for blood pressure

A

Cardiac output x total peripheral resistance

34
Q

What is the Total peripheral resistance

A

Arterial vascular resistance

35
Q

What is oulse pressure

A

Pressure at systole - pressure at diastole

CAR (15 decks)

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