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60 > L11 - regional control of blood flow > Flashcards

L11 - regional control of blood flow Flashcards

1
Q

list the ways blood flow can be increased / decreased

A
  1. ANS
  2. active hyperaemia (metabolic)
  3. functional hyperaemia (metabolic)
  4. reactive hyperaemia (metabolic)
  5. flow auto regulation (metabolic and pressure)
  6. endocrine (hormonal)
  7. paracrine
  8. PO2
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2
Q

define hyperaemia

A

increased blood flow

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3
Q

define active hyperaemia

A

blood flow increases to a tissue because it is metabolically active and needs more O2 / fuel

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4
Q

define functional hyperaemia

A

when an organs normal function requires cyclical drops in pressure, so flow must increase cyclically to compensate

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5
Q

define reactive hyperaemia

A

blood flow increases to compensate for prolonged periods of reduced pressure and flow

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6
Q

explain process of active hyperaemia

A
  1. increased work being done in muscle = more O2 and glucose consumption
  2. decrease PO2
    increased metabolite production
    increased heat
    increased PCO2 (decreased pH)
  3. local vasodilation
  4. increased blood flow to that tissue
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7
Q

define flow auto regulation

A

tissue that can regulate its own blood flow

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8
Q

what does higher tone mean?

A

higher degree of arteriole contraction

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9
Q

what two factors control flow auto regulation (and in what way)

A
  1. pressure (increased pressure = decreased flow)

2. metabolic (metabolite accumulation = increased flow)

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10
Q

describe process of flow autoregulating by pressure

A
  1. increased pressure stretches arterioles
  2. increases smooth muscle tone
  3. local vasoconstriction
  4. decreased flow
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11
Q

why is flow auto-regulation important?

A

exercise increases CO and therefore flow throughout whole body, but some tissues want to maintain normal flow

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12
Q

describe process of flow autoregulating by metabolites

A
  1. normal tissue function involves cyclical compression of arterioles (eg heart)
  2. causes cyclical decrease in
    blood pressure
    blood flow
    O2
    and cyclical increase in
    metabolite accumulation
  3. cyclical local vasodilation
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13
Q

what is functional hyperaemia the same as

A

flow auto regulation by metabolites

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14
Q

what is reactive hyperaemia a form of?

A

flow auto regulation by metabolites

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15
Q

describe process of reactive hyperaemia (flow autoregulation)

A
  1. prolonged period of reduced blood pressure and flow leads to
    increased metabolite accumulation
    decreased O2
  2. exaggerated local vasodilation
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16
Q

what are the functions of hormonal control of regional blood flow

A
  1. regulate blood flow to metabolic demand (like other methods)
  2. maintain MABP, blood vol and osmolarity etc)
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17
Q

what effect does adrenaline have on skeletal muscle and why

A

vasodilation (binds to b receptors)

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18
Q

in what tissues does adrenaline cause vasoconstriction and why

A

elsewhere to skeletal muscle

acts on a receptors

19
Q

when might there be paracrine control of regional blood flow

A

responding to inflammation

regulating MABP

20
Q

describe process of paracrine control of regional blood flow (vasodilation)

A
  1. local mediators (eg range of vasodilators) act on endothelium causing it to release NO
  2. NO causes SM relaxation - vasodilation
21
Q

describe process of paracrine control of regional blood flow (vasoconstriction)

A
  1. local mediators (constrictors) act on endothelium which releases endothelin
  2. endothelin causes SM constriction - vasoconstriction
22
Q

what are the substances responsible for paracrine control of regional blood flow

A

NO (dilation)

endothelin (constriction)

23
Q

what controls skeletal muscle blood flow at rest

A

determined by SNS and myogenic tone

24
Q

what controls skeletal muscle blood flow during exercise

A
  1. arteriolar tone - determined by local metabolites
  2. blood flow - determined by
    flow auto regulation
    active hyperaemia
25
Q

what is the effect of adrenaline on blood flow

A
  1. will vasodilate skeletal muscle arterioles (b receptors)

2. will constrict elsewhere in body (a receptos)

26
Q

(if not compensated) what will cause blood flow to heart to decrease?

A
  1. increased HR
  2. decreased aortic pressure
  3. increase in LVEDP (left ventricle end diastolic pressure)
27
Q

when is blood flow to heart at its peak

28
Q

what waste products accumulate in heart muscle during exercise

A
  1. adenosine (ATP usage)
  2. K+ (repeated repolarisations)
  3. increased PCO2
  4. increased lactic acid
29
Q

what is regional active hyperaemia

A

control of blood flow matched to metabolic demand in regions of brain

30
Q

what happens to blood flow in brain if CO falls

A

maintained by cerebral vasodilation, even at expense of other tissues

31
Q

what happens to blood flow in brain if CO increases

A

cerebral vasoconstriction

32
Q

what two factors control cerebral regional blood flow

A 
metabolic
myogenic tone (pressure)
33
Q

explain effects of hyperventilation on brain

A
  1. breathing rate beyond what is required
  2. decreases PCO2
  3. vasoconstriction
  4. flow in brain decreases below what is needed - dizziness
34
Q

how is the effects of hyperventilation on brain compensated

A
  1. hyperventilation also causes decrease in PO2

2. this causes vasodilation

35
Q

what is skin blood flow mainly controlled by?

36
Q

where is thermoregulatory centre

A

hypothalamus

37
Q

how do skin arterioles respond to increase in core temp

A
  1. rise in temp recognised by hypothalamus which decreases SNS firing
  2. arterioles in skin dilate
  3. increase in skin blood flow
38
Q

why does the blood flow system in the lungs have to be different?

A

it is low pressure low resistance as it has to accommodate for the same amount of blood as the systemic circulation

39
Q

what do arterioles in lungs do to respond to a decrease in CO (pressure)

A

they increase resistance

40
Q

what do arterioles in lungs do to respond to a increase in CO (pressure)

A

they decrease resistance

41
Q

how is blood flow system in lungs different

A

it is a passive mechanical response to changes in pressure

42
Q

explain process of lungs responding to increase in pressure (co)

A
  1. at rest pulmonary arteries are closed due to alveolar pressure
  2. increase in blood pressure opens these (recruitment)
  3. very high increase in blood pressure distends these PAs
43
Q

explain process of lungs responding to decrease in pressure (co)

A
  1. many PAs remain closed to increase total resistance (less tubes in parallel)
44
Q

what is recruitment

A

opening of PAs in response to increase in pressure to maintain flow

60 (27 decks)

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