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physiology exam 3 > regional circulation > Flashcards

regional circulation Flashcards

1
Q

what is autoregulation

A

ability of an organ to maintain constant blood flow despite changes in pressure

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2
Q

what are the organs that autoregulate

A
  • heart
  • brain
  • kidneys
  • skeletal muscle
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3
Q

what is the relationship between metabolic activity and coronary blood flow

A
  • linear relationship. As metabolic activity goes up, the tissue requires more oxygen and the blood flow to the organ increases
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4
Q

compression effect of systole occurs mainly on which coronary vessel

A

left coronary artery

  • reduction of flow occurs in left coronary artery during early systole, whereas it does not occur in right coronary artery
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5
Q

What are the major local metabolites that signals an increase in O2 consumption and lead to active hyperemia

A
  • adenosine
  • nitric oxide

**vasodilators

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6
Q

what effect does NE acting on a-1 receptors have on the arteries/arterioles?

A

vasoconstriction

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7
Q

what effect does sympathetic stimulation via epinephrine acting on B-2 receptors have on the arteries/arterioles?

A

vasodilation of vessels

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8
Q

what is the net effect of sympathetic stimulation of the heart

A

increase coronary blood flow

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9
Q

in the adaption of long term reduction to flow, hypoxia induced what factor? What is the effect?

A
  • hypoxia induced factor (HIF)
  • angiogenesis
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10
Q

blood brain barrier consists of what type of junctions between endothelial cells which prevents large circulating vasoactive peptides from altering blood flow

A

tight junctions

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11
Q

cerebral ciculation is controlled almost entirely by what?

A

local metabolism

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12
Q

what is the most important local vasodilator

A
  • CO2 (or H+)
    • vessels dilate to increase CO2 and protons
    • constrict if CO2 and proton content decrease
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13
Q

what effect does an increase in cerebral PCO2 have?

A
  • vasodilation
  • increased BF to remove excess CO2
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14
Q

which elicits a more dramatic and rapid change in blood flow: local change in CO2 or O2?

A

CO2

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15
Q

what is the primary regulator of cerebral blood blow?

A

METABOLISM

  • reflects increased nerve action potentials
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16
Q

effect of adenosine of cerebral circulation

A

released from hypoxic tissues and DILATES cerebral vessels

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17
Q

effect of K+ on cerebral circulation

A

released by active neurons can have a dilating action on cerebral vessels

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18
Q

effect of NO of cerebral circulation

A

NO from endothelium and neurons/glia cells causes cerebral vasodilation

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19
Q

how involved is sympathetic innervation to change cerebral circulation

A

weak

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20
Q

Why does chronic hypertension not cause increased cerebral blood flow?

A

with hypertension, vascular resistance increases allowing cerebral BF to be normal

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21
Q

in chronic hypertension, autoregulation range doubles (60 to 100 mmHg). What is the drawback?

A

partial loss of ability to vasodilate and regulate BF at low pressures

22
Q

edema that causes intracranial pressure to increase causes what reflex?

A

cushing’s reflex

23
Q

what is cushing reflex?

A
  • as intracranial pressures increase, areas in the brain becomes compressed, hypoxic and ischemic
  • cushing reflex: venules collapse; venous resistance increases causes capillary pressure to rise which favors filtration which further increases intracranial pressure
  • this response will activate the sympathetic nervous system -> raises MAP which causes increases cerebral blood flow

*cushings response will improve flow but worsen the edema

24
Q

what is the total blood flow to skeletal muscles at rest

A

750-1000 mL/min

25
Q

what is the total blood flow to skeletal muscles at exercise

A

15,000-20,000 mL/min

26
Q

what is capillary recruitment in response to exercise?

A
  • at rest, 25% of capillaries are perfused
  • with exercise, more capillaries are perfused, increasing the number of flowing capillaries
27
Q

blood flwo to skeletal muscle is controlled by what?

A
  1. local metabolites
  2. sympathetic innervation
  3. autoregulation (minor)
28
Q

at rest, increased basal vascular tone by sympathetic innervation is done via what neurotransmitters?

A
  • increase in NE to a-1 adrenergic
  • decrease in epineprhine to B-2 adrenergic
29
Q

with exercise, vascular resistance is decreased and vasodilation predominates via what mechanisms?

A
  1. decreased sympathetic a-1 adrenergic tone
  2. increased muscarinic tone (acetylcholine)
  3. increased sympathetic B-2 adrenergic tone
30
Q

how is blood flow to muscle increases during exercise?

A

sympathetic vasoconstriction of “non-exercisng” tissues increase resistance, shunting blood to exercing tissues

31
Q

change in blood flow to skeletal muscle during exercise reflects the following 5 signs:

A
  1. increased CO
  2. decrease flow to kidney, gut and bone
  3. hyperemic response
  4. autoregulation
  5. decreased unstressed volume
32
Q

active hyperemia in skeletal muscle is driven by which local metabolites

A
  • lactate
  • adenosine
  • K+
33
Q

describe blood flow response to muscle during rhythmic exercise

A

mean flow increases with muscle activity but flow is phasic

  • ​decreases during contraction and increases with relaxation
34
Q

describe blood flow response to muscle during sustained contraction

A
  • mean flow decreases during the contraction, followed by a post contraction hyperemic response when contraction ends
35
Q

function of muscle venous pumps?

A
  • lowers the venous pressure which increases the pressure gradient
  • driving flow of blood to the right atrium
  • muscle pump function promotes lower venous and capillary pressures in feet and lower limbs
36
Q

function of arginine vasopressin on vessels. What receptor is used?

A

vasoconstriction via AVP 1-A receptor

37
Q

function of angiotensin II on vessels. What receptor is used?

A

vasoconstriction via AT-1 receptor

38
Q

function of atrial natriuretic peptide on vessels. What receptor is used?

A

vasodilation by acting on natriuretic peptide receptors A/B (NP-A, NP-B)

39
Q

total blood flow to the skin during rest

A

200-500 mL/min

40
Q

total blood flow to the skin during exercise

A

700-1000 mL/min

41
Q

primary role of blood flow to skin

A

allow for heat exchange

42
Q

local nutritional blood flow through the precapillary spincters and capillaries is under control of what?

A

vasodilator metaoblites and sensory stimuli (temp, touch, pain)

43
Q

blood flow to the skin is under control of what

A

hypothalamic thermoregulatory centers that adjust sympathetic outflow

44
Q

what is considered apical skin

A
  • present on nose, lips, ears, hand, fingertips, nailbeds, soles of feet
    • these tissues have a high surface to volume ratio that favours heat loss
    • contain glomus bodies
45
Q

sympathetic effect of apical skin

A

release NE causing vasoconstriction

46
Q

what is nonapical skin

A
  • remaining cutaneous locations
    • lack glomus bodies
47
Q

sympathetic effect on nonapical skin

A
  • release NE causing vasoconstriction
  • sympathetic cholinergic fibers release Ach, causing vasodilation via action of bradykinin
48
Q

AV anastomoses are under what control

A

neural control

  • sympathetic fibers release NE and constrict arteriole and AV anastomeses
49
Q

symmpathetic tone is increases in what core temp?

A

when core temp is decreased

  • decreases blood flow to minimize heat loss
50
Q

as intensity of exercise increases, blood flow to skin increases, except at maximal exercise capacity, what happens to blood flow to skin ?

A

decreases

51
Q

compaire sympathetic control, metabolic control, and autoregulation effects on coronary, cerebral and skeletal muscle vascular control

A
  • coronary: symp control: +; meta control: +++; autoreg: +++
  • cerebral: symp control: +; meta control: +++; autoreg: +++
  • skeletal muscle: symp control: ++; meta control: +++; autoreg: ++

physiology exam 3 (7 decks)

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