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SMP - Cardiopulmonary Exam 1 > Lecture 15 - Local Regulation of Blood Flow > Flashcards

Lecture 15 - Local Regulation of Blood Flow Flashcards

1
Q

List organs from highest blood outflow in therms of % of CO to lowest AT REST.

A
  1. Liver
  2. Muscle
  3. Kidney
  4. Brain
  5. Skin
  6. Heart
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2
Q

List organs from highest O2 EXTRACTION from blood to lowest AT REST.

A
  1. Heart
  2. Brain
  3. Liver and muscles
  4. Skin
  5. Kidney
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3
Q

What is the organ that receives the highest percentage of the CO?

A

Lungs: 100%

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4
Q

Combined, what fraction of the CO do the liver and the GIT receive?

A

1/3

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5
Q

What 2 organs receive the largest amount of blood per mass of tissue? Why?

A
  1. Kidneys, because they filter blood instead of using the O2 in the blood
  2. Liver because it filters the blood to uptake and release metabolic compounds
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6
Q

What are the 2 most metabolically active tissues of the body at rest?

A

Brain and heart

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7
Q

What do the varied flows of blood from organ to organ reflect?

A

The different functions of the tissues: metabolism, blood filtration, thermoregulation, etc.)

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8
Q

Which organ consumes the least oxygen?

A

Kidneys

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9
Q

What are the 3 mechanisms of local control of blood flow?

A
  1. Metabolic regulation
  2. Autoregulation
  3. Shear stress induced vasodilation
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10
Q

What do local mechanisms of blood flow control?

A

Flow in the local vascular bed

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11
Q

What do neurohumoral mechanisms of blood flow control?

A
  1. Regulation of BP and BV over the long-term through regulation of fluid and electrolytes levels
  2. Patterns of flow in regional circulations in a non-uniform manner in altered physiological states: exercise, volume depletion, etc.
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12
Q

Describe metabolic regulation of blood flow.

A

Increased metabolism => tissue cells produce metabolic products, which in general are vasodilators => vasodilation of precapillary sphincters and arterioles => increased blood flow to remove the waste products

When metabolism decreases back to baseline, there will be a short lag time before the blood flow goes back to baseline (also a lag time to increase blood flow)

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13
Q

What is the rate of blood flow proportional to during metabolic regulation? How come?

A

Propotional to the rate of metabolism because tissues release metabolic products in proportion to the level of metabolism

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14
Q

What are the 2 types of metabolic regulations of blood flow? Describe each.

A
  1. Active hyperemia = increased blood flow during periods of increased metabolism
  2. Reactive hyperemia = increased blood flow after occlusion
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15
Q

What are 7 examples of metabolic products that regulate blood flow?

A
  1. CO2
  2. H+
  3. K+
  4. Adenosine
  5. Lactate
  6. Prostaglandins
  7. Low O2
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16
Q

Is metabolic regulation of blood flow endothelium dependent or independent?

A

Independent

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17
Q

What does hyperemia mean?

A

Increased blood flow

18
Q

What is the removal rate of metabolic products proportional to?

A

Blood flow

19
Q

Other name for autoregulation of blood flow?

A

Myogenic regulation

20
Q

Describe autoregulation of blood flow. Purpose?

A

Increase in transmural pressure of the arteriole/capillary sphincter => stretched smooth muscle => depolarization of smooth muscle => contraction => decreased vessel diameter (or opposite mechanism with hyperpolarization)

Purpose: ability to normalize flow in the face of fluctuating transmural pressure to keep local flow relatively constant

21
Q

When is the autoregulation of blood flow not active in arteries in muscles and organs?

A

At the normal arteriolar transmural pressure (MAP) = 100 mmHg

22
Q

In what range of intramural pressures is autoregulation of blood flow effective?

A

60 to 160 mmHg

23
Q

Is autoregulation of blood flow endothelium dependent or independent?

A

Independent

24
Q

Does flow need to also increase along with increased transmural pressure in order for the autoregulation of blood flow to kick in?

25
Q

Describe shear-stress induced vasodilation.

A

Increased flow => greater shear stress => endothelium synthesizes NO => dilates smooth muscle

26
Q

Is shear-stress induced vasodilation endothelium dependent or independent?

27
Q

Does transmural pressure need to also increase along with increased flow in order for the shear-stress induced vasodilation to kick in?

28
Q

How can you keep transmural pressure constant but alter flow?

A

Profuse on both sides of a vessel and ensure that the mean of the pressures on each end is always constant (if you increase on side you need to decrease the other) but vary the gradient to cause a change in blood flow

29
Q

In the resting state, arterial pressure goes up due to stress. What happens to blood flow to resting skeletal muscle?

A

Flow stays relatively constant due to autoregulation

30
Q

Skeletal muscle is working during aerobic exercise. What happens to blood flow? What to note?

A

Metabolic vasodilation => reduced resistance to that bed => flow increases => higher shear stress in the arterial system supplying that area => vasodilation further augmenting flow to the working muscle

Note: myogenic regulation and SNS constriction are overridden by metabolic regulation and shear stress in these vascular beds

31
Q

What is shear stress caused by?

A

Differences in longitudinal pressure aka the pressure gradient between 2 ends of a tube

32
Q

How to calculate transmural pressure?

A

In the middle of the tube it is the average of the pressures at each end of the tube

33
Q

How do our bodies make sure that blood does not flow to metabolically inactive organs and shunts blood to the metabolically active organs regardless of systemic pressure?

A
  1. Metabolically active organs cause vasodilation in vessels closest to the tissues => increase in longitudinal pressure gradient => increase in shear stress => more vasodilation
  2. Metabolically inactive organs receive increased systemic pressure but longitudinal pressure remains the same => increased transmural pressure => myogenic regulation to vasoconstrict
34
Q

Does arterial pressure vary during aerobic exercise?

A

Not really - relatively constant

35
Q

Does pulse pressure vary during aerobic exercise?

A

YUP - goes up

36
Q

What are 3 examples of tissues that are more responsive to metabolic control of flow than sympathetic control of flow?

A
  1. Skeletal muscles
  2. Heart
  3. Brain (local level flow ONLY - overall flow is always constant)
37
Q

What max % of CO can skeletal muscles get during exercise?

A

80% of 25 L/min CO

38
Q

What are 3 examples of tissues that are more responsive to sympathetic control of flow than metabolic control of flow? Why?

A
  1. Kidneys
  2. Skin
  3. Splanchnic organs

=> not needed for the fight or flight reponse

39
Q

How can you keep flow constant but alter transmural pressure?

A

Profuse on both sides of a vessel and ensure that the pressure gradient is unchanged but vary the mean of the pressures on each end

40
Q

Difference in flow patterns in reactive and active hyperemia?

A

Reactive hyperemia has less of a lag time to increase flow

SMP - Cardiopulmonary Exam 1 (28 decks)

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