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CardioPulm > 12.7 A > Flashcards

12.7 A Flashcards

1
Q

What three organs get most of the resting blood flow?

A

liver, kidney, muscle

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2
Q

Why does resting blood flow differ between organs?

A

because although MAP is the same throughout the system, the resistance in each organ is different

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3
Q

Describe the pressure gradient that pushes blood across the various organs.

A

each has an equal pressure gradient since they’re in parallel

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4
Q

The heart and brain are unique in that their vascular tone is primarily controlled by what?

A

vasodilator metabolites whereas other organs are more dependent on sympathetic innervation

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5
Q

Is the basal tone for arteries constriction or dilation?

A

their basal tone leans more towards constriction

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6
Q

Oxygen uptake into an organ depends on what factors?

A
  • rate of blood flow

- ability to extract oxygen

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7
Q

Oxygen uptake by an organ can be calculated with what equation?

A

O2 uptake = blood flow x [(A-V)O2 Difference]

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8
Q

What determines the ability of an organ to extract oxygen from blood?

A

the total surface area of perfused capillaries, which is controlled by precapillary sphincters

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9
Q

How do precapillary sphincters affect organ oxygen extraction?

A

they alter the total surface area of perfused capillaries to alter the organs ability to extract oxygen

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10
Q

How does basal oxygen extraction differ in the heart from other organs like the kidney?

A

there are no precapillary sphincters in the heart, so all capillary beds are perfused and oxygen extraction is always maximal

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11
Q

Although kidneys have precapillary sphincters, they are unable to significantly alter what in order to increase oxygen uptake.

A

the kidney is limited in its ability to increase blood flow

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12
Q

What is autoregulation?

A

the ability of the heart and brain to maintain relatively constant blood flow in response to changes in systemic arterial pressure

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13
Q

What is the autoregulatory range?

A

the range of MAPs across which organs are capable of maintaining steady state organ blood flow

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14
Q

The limits of autoregulation represent what quality of the organ’s arteries?

A

maximal dilation or constriction

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15
Q

When arterial pressure drops, what happens to the arterioles of systemic organs? What about to the arterioles of the brain and heart?

A
  • systemic arterioles will contract

- brain and heart arterioles will dilate

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16
Q

Which organs are capable of autoregulation?

A

the brain and heart

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17
Q

Autoregulation involves what two mechanisms?

A
  • myogenic response where changes in vascular pressure alter stretch of the vessel wall, resulting in constriction or dilation
  • changes in the level of metabolic vasodilators in interstitial fluid of the organ
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18
Q

Describe the myogenic response that underlies changes in regional blood flow.

A
  • increase in arteriolar pressure
  • increased stretch of the wall
  • increased frequency of APs in smooth muscle
  • opening of calcium channels
  • calcium influx
  • contraction/constriction
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19
Q

The interstitial concentration of vasodilator metabolites is controlled by what factors?

A
  • rate of formation (proportional to metabolic rate)

- rate of removal (proportional to organ blood flow)

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20
Q

What are some vasodilator metabolites?

A
  • adenosine
  • potassium
  • lactic acid
  • carbon dioxide
21
Q

When ATP formation is impaired, what vasodilator metabolite level rises?

A

adenosine

22
Q

How does potassium serve as a vasodilator metabolite?

A
  • when frequency of APs increases interstitial concentration of potassium rises
  • local hyperkalemia causes hyperpolarization of arterioles which decreases calcium influx to smooth muscle
  • causes relaxation
23
Q

Decreased ATP levels have what effect on interstitial potassium levels?

A

decreased ATP levels activate K/ATP channels which increases potassium efflux and results in hyperkalemia which decreases calcium influx to smooth muscle, leading to relaxation

24
Q

All vasodilators do what on an ionic level?

A

decrease calcium levels within vascular smooth muscle

25
Q

What is active hyperemia?

A

increased blood flow to an organ due to an increase in metabolic activity of the organ

26
Q

Which vasodilator metabolites are responsible for mediating active hyperemia?

A
  • adenosine
  • potassium
  • lactic acid
  • carbon dioxide
27
Q

Give an example of active hyperemia?

A

exercise causes active hyperemia in skeletal muscle

28
Q

What is reactive hyperemia?

A

a phenomenon where blood flow is transiently increased following a brief period of total ischemia

29
Q

What is a good example of reactive hyperemia?

A

use of a blood pressure cuff

30
Q

Describe whats happening during reactive hyperemia due to a blood pressure cuff.

A
  • cuff is inflated and blood flow is cut off
  • vasodilator metabolites start to form and dilate the vessels and there is a myogenic response
  • when cuff is released, blood flow is immediately higher than it was before the cuff went on
  • then it gradually drops back to normal
31
Q

How much must arterial blood partial pressure of oxygen drop before cerebral blood flow increases?

A

partial pressure must drop roughly 50%

32
Q

Why does it take a 50% drop in arterial blood partial pressure of oxygen before cerebral blood flow increases?

A

due to the nature of hemoglobin, oxygen content isn’t really reduced until the partial pressure of oxygen is cut in half

33
Q

What is hypercapnia?

A

increased arterial partial pressure of carbon dioxide

34
Q

When carbon dioxide levels in the brain drop, what happens to arterioles?

A

they constrict in an effort to build up CO2 and maintain a stable pH

35
Q

Why does the brain attempt to maintain a constant pCO2?

A

because it needs to maintain a stable pH

36
Q

Oxygen delivery to the heart is mainly controlled by changes in what factor?

A

rate of blood flow with little change in oxygen extraction

37
Q

MIs are most common where in the heart muscle?

A

LV subendocardium

38
Q

Why are MIs more common in the subendocardium?

A

because during systole, vessels in the left ventricle are compressed due to the high pressure developed within the ventricle and this decreases coronary blood flow

39
Q

Left coronary blood flow mainly occurs when during the cardiac cycle?

A

ventricular diastole

40
Q

What are the four determinants of myocardial oxygen demand?

A
  • inotropic state
  • intraventricular pressure
  • heart rate
  • end diastolic volume
41
Q

What is the most costly determinant of cardiac oxygen consumption?

A

inotropic state because a 100% increase in inotropic state increases oxygen consumption by 200%

42
Q

What factor is capable of increasing cardiac output without significantly increasing the myocardial oxygen demand?

A

increasing end diastolic volume

43
Q

Decrease in tissue oxygen levels within the lung cause what arteriolar change?

A

vasoconstriction so that blood flows to the better oxygenated areas of tissue

44
Q

If hypoxia occurs throughout the lungs, this causes what problem?

A

widespread pulmonary arteriolar constriction, increasing pulmonary resistance and elevating pulmonary artery pressure causing right ventricular hypertorphy

45
Q

What is the role of portal circulation?

A

transoprt of blood from one capillary bed in a splanchic organ to another capillary bed in the liver

46
Q

The liver receives a blood supply from what two sources?

A

the heart and from splanchic organs via the portal vein

47
Q

Edema can arise in splanchnic organs due to what?

A

portal hypertension which increases venous pressure in splanchnic veins

48
Q

What is a major cause of portal hypertension?

A

cirrhosis

CardioPulm (31 decks)

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