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Cardiovascular System (Milly's) > Introduction and control of cardiac output > Flashcards

Introduction and control of cardiac output Flashcards

1
Q

Why do we need a cardiovascular system?

A

All living organisms are metabolically active and we have too large a SA:Volume ratio for diffusion to be efficient

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2
Q

What type of epithelium make up capillaries?

A

Simple squamous endothelial cells (and basement membrane/basal lamina)

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3
Q

What 3 things does rate of diffusion depend on?

A

Area available for exchange,
Diffusion resistance,
Concentration gradient

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4
Q

How is the capillary density effected by highly metabolic tissues?

A

The capillary density is increased

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5
Q

When might the blood in capillaries have a lower concentrations of a substance than the arterial blood?

A

If that substance is used by the tissues

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6
Q

If you have a slow blood flow how would this effect the capillary concentration of a given substance?

A

It would lower the capillary concentration (because the substance is removed from the blood more)

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7
Q

Why is the maintenance of blood flow so important in capillary beds?

A

It creates a constant concentration gradient which drives the diffusion of substances (eg Oxygen)

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8
Q

What is the perfusion rate?

A

The rate of blood flow

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9
Q

How are increases in metabolism met by the cardiovascular system?

A

By increased blood flow

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10
Q

Name the organ that requires a constant flow of blood

A

The brain/ kidneys

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11
Q

What is the blood flow in l/min at rest? (On average)

A

5 litres/min

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12
Q

During exercise what is the max flow of blood in l/min? (On average)

A

25 litres/mins

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13
Q

What is the heart surrounded by?

A

The pericardial sac

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14
Q

How many layers is the pericardial sac?

A

3
Fibrous layer
Parietal serosa
Visceral serosa

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15
Q

What is the fat that surrounds the heart called?

A

Epicardial fat

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16
Q

What is the visceral layer of the heart attached to?

A

The myocardium

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17
Q

How and why can a rapid increase in fluid within the pericardial cavity be damaging?

A

It compresses the heart due to the inextensible fibrous pericardial layer
The fibrous layer does not ‘give way’ when fluid builds up

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18
Q

What can compression of the heart lead to?

A

Cardiac tamponade

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19
Q

How might fluid be removed from the pericardial cavity to relieve compression?

A

Perform a Pericardiocentesis

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20
Q

What is the transverse pericardial sinus?

A

The space (approx. 1 finger width) that is behind the superior vena cava, ascending aorta and pulmonary trunk.

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21
Q

What is the space that is behind the superior vena cava, ascending aorta and pulmonary trunk called?

A

Transverse pericardial sinus

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22
Q

What is the pericardium attached to? (3)

A

Sternum and the mediastinal portions of the right and left pleurae

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23
Q

What is the apex of the heart?

A

The tip of the left ventricle, which points inferiority, anteriorly and to the left

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24
Q

Where is the base of the heart?

A

Formed by the atria (mainly the left), essentially the top of the heart
Lies between the lung hila

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25
Q

What does the anterior surface of the heart consist of?

A

The right and left ventricles (L atrium and ventricles lie more posteriorly and form only a small strip of the anterior surface)

26
Q

What forms the inferior surface of the heart?

A

Both ventricles (the left predominantly)

27
Q

Why is the inferior face of the heart also called the diaphragmatic surface?

A

Because it lies along the diaphragm

28
Q

Where do the L and R coronary arteries stem from?

A

At the root of aorta, just above the aortic valve (in sinuses)

29
Q

Where does the Left anterior descending artery travel to in the heart?

A

Down the front (border of ventricles)

30
Q

Where does the circumflex arteries travel to in the heart?

A

Round the back and down

31
Q

Where does the R coronary artery in the heart run?

A

Along the AV groove

32
Q

Where does the R marginal artery run in the heart?

A

Round bottom front face, travels R->L

33
Q

How many pulmonary veins are there?

34
Q

What is the coronary sinus?

A

The coronary sinus is a collection of veins joined together to form a large vessel that collects blood from the heart. It delivers deoxygenated blood to the right atrium

35
Q

What is special about the coronary arteries that make them similar to the splenic artery for example?

A

They are end arteries

36
Q

What is afterload in terms of the heart?

A

Here are some explanations:

Afterload is the pressure in the wall of the left ventricle during ejection. (roughly equivalent to aortic pressure)

After-load is the pressure against which the heart must work to eject blood during systole .

In other words, it is the end load against which the heart contracts to eject blood

37
Q

What is preload in terms of the heart?

A

Amount the ventricles are stretched (filled) in diastole- related to the end diastolic volume or central venous pressure

it is the initial stretching of the cardiomyocytes prior to contraction (it is related to the sarcomere length at the end of diastole)

38
Q

What is total peripheral resistance in terms of the heart?

A

Resistance to blood flow offered by all systemic vasculature

39
Q

What is another word used to describe total peripheral resistance (TPR)?

A

Systemic vascular resistance

40
Q

What two things (in terms of shape of the heart) occur during ventricular contraction?

A

Radial thickening

Longitudinal shortening

41
Q

What blood vessels offer the greatest resistance?

A

Arterioles

42
Q

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

A

The pressure drops as it flows through ‘a resistance’

43
Q

What will happen to the pressure on the capillary/venous and arterial sides if there is arterioles constriction?

A

The capillary/venous side- pressure decreased (because its after the resistance)
The arterial side- pressure increase (because it before the resistance)

44
Q

What happens to the arterial and venous pressures if the TPR falls and Cardiac output (CO) is unchanged?

A

Arterial pressure decreases

Venous pressure increases

45
Q

What happens to the arterial and venous pressures if the TRP increases and the CO is unchanged?

A

Arterial pressure increase

Venous pressure decreases

46
Q

What happens to the arterial and venous pressures if Cardiac output increase and TPR is unchanged?

A

Arterial pressure increases

Venous pressure decreases

47
Q

What happens to the arterial and venous pressures if the Cardiac output is decreased and the TPR is unchanged?

A

Arterial pressure decreases

Venous pressure increases

48
Q

What dilates to allow greater blood flow to a tissue?

A

Arterioles and pre-capillary sphincters

49
Q

If vasodilation has occurred what does this mean for the TPR and subsequently the venous and arterial pressure and the cardiac output?

A

TPR will decrease, meaning arterial blood pressure (aBP) will drop (whilst central venous pressure {CVP} rises), therefore in order to maintain constant pressure in arterioles, the heart increases its output, cardiac output increases. This also prevents the venous pressure from rising too much

50
Q

By which mechanisms does the heart respond to changes in CVP and aBP? (2)

A

Intrinsic and extrinsic

51
Q

What is the equation for cardiac output?

A

Stroke volume x heart rate

52
Q

What is the equation for stroke volume?

A

End diastolic volume-end systolic volume (EDV-ESV)

53
Q

How will a change in contractility change the starling curve?

A

It will increase the force of contraction for a given EDP

54
Q

How can the heart increase its contractility?

A

Extrinsic factors ie sympathetic stimulation and circulating adrenaline

55
Q

What is afterload in the heart?

A

The pressure that the heart has to pump against

56
Q

When would arterial pressure increase?

A

When the peripheral resistance is increase (this makes it harder for the heart to pump out)

57
Q

What factors determine cardiac output?

A

How much the ventricle empties which depends on

  • how hard it contracts (determined by the EDV- how much heart fills and contractility- increased by sympathetic drive)
  • how hard it is to eject blood (approx. Arterial pressure)
58
Q

If the metabolism of the body increases what happens to the TPR? What does this mean fore arterial and venous pressures? And how does the heart respond?

A

It will fall to supply more blood

Arterial pressure decreases
Venous pressure increases

Heart pumps more

59
Q

What happens to the venous and arterial pressures and the cardiac output when one stands? How is this effect changed? What could happen if these changes aren’t brought about?

A

Venous pressure falls-due to gravity
Causing cardiac output to fall
Which in turn causes arterial pressure to fall

Baroreceptor reflects and autonomic system increases HR and increase tpr

Postural hypotension

60
Q

What does the body do in order to increase cardiac output during exercise?

A 
Increases venous pressure (by venoconstriction initially and then by a decrease in TPR) 
Increase heart rate (increased sympathetic drive)
Increase contractility (increased sympathetic drive)
61
Q

What do intrinsic control mechanisms of the heart ensure?

A

That the output of the left and right ventricles match

Cardiovascular System (Milly's) (28 decks)

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