Topic 30 - Local factors of cardiovascular regulation Flashcards

1
Q

Words to include

A
  • Perfusion (blood flow)
  • Oxygen demand
  • Nutrient demand
  • Tissues
  • Collapse of normal circulation
  • Inproportional blood supply
  • Local regulatory mechanisms
  • Paracrine signals
  • Central regulation
  • Local regulation
  • Short run
  • Long run
  • Intrinsic (local) short term regulation
    • Autoregulation by myogenic tone
      • Microcirculation
        • Peripheral blood pressure
      • Bayliss effect
        • Metarterioles
        • Pressure change
        • Perfusion (ml /min)
        • Blood pressure (mmHg)
        • Metabolic demand
        • Ischemia
        • Normal perfusion
        • Hyeremia
        • Metarteriole sphincter
          • Constriction
          • Relaxation
    • Endothelial related regulation
      • Endothelial cells
      • Humoral signals
      • Smooth muscles (in vessel wall)
      • Endothelium derived relaxing factor (EDRF)
        • Nitrogen monoxide (NO)
          • cGMP
        • Prostacyclin
          • cAMP
        • Endothelial-factor unrelated to NO and prostacyclins
      • Endothelium derived contracting factor
        • Endothelins (ET 1-4)
        • Cyclooxygenase dependent factor
          • TXA2
          • NO degradation
        • Angiotensins-II
          • Vasoconstrictor
          • Endothelins
          • Sympathetic vasoconstriction
    • Acetylcholine
      • Nerve endings
        • Vasoconstriction
      • Lumen of blood vessel
        • Endothelium
        • Vasodilation
    • Regulation through metabolites
      • O2-consumption (↑)
      • Adenosine concentration (↑)
      • H+ concentration (↑)
      • CO2 concentration (↑)
      • K+ concentration (↑)
      • EDRF stimulation
      • NO production (↑)
      • cGMP (↑)
      • Hypoxia
  • Intrinsic (local) long term regulation
    • Growth factors
    • Enzyme induction
    • Angiotensins
    • Hyperemia
      • Active hyperemia
      • Reactive hyperemia
        • Secondary increase
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2
Q

Intrinsic (local) regulation

General

A
  • Either:
    • Short term
    • Long term
  • Regulated by fast, local, auto-regulative processes
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3
Q

What is intensity of perfusion (blood flow) determined by?

A

Oxygen and nutrient demand of the organ

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4
Q

Intrinsic (local) short term regulation

Local factors

A
  • Tissues adjust their own perfusion by local factors:
    1. Autoregulation by myogenic tone
    2. Endothelial related regulation
    3. Acetylcholine
    4. Regulation through metabolism
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5
Q

Intrinsic (local) short term regulation

Local factors: autoregulation by myogenic tone

A
  • Microcirculation should not be influenced by the changes of peripheral blood pressure
  • Bayliss effect
    • Pressure changes initiate adequate response of metarterioles sphincters
    • Perfusion will adapt to the metabolic demand
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6
Q

Intrinsic (local) short term regulation

Local factors: endothelial related regulation

A
  • Blood pressure mechanically deforms endothelial cells
    • Promotes the endothelial cells to produce humoral signals that influences the contraction state of smooth muscles in the wall of the vessels
  • Two major classes of such factors:
    1. Endothelium Derived Relaxing Factor (EDRF)
      • Nitrogen monoxide
        • Penetration to smooth muscle, cGMP ↑ = smooth muscle relaxation
      • Prostacyclin
        • NO production ↑
        • Direct muscle relaxation effect, by cAMP ↑
      • Endothelial-factor
        • Hyperpolarization by activating ATP dependent K-channels
          • K+is anindirect vasodilator
    2. Endothelium Derived Contracting Factor (EDCF)
      • ​​Endothelins (constrictor)
      • Cyclooxygenase dependent factor
        • ​TXA2
        • Stimulates NO degradation
      • Angiotensins-II
        • ​Direct vasoconstrictor
        • Stimulates production of endothelins
        • Sympathetic vasoconstriction ↑
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7
Q

Intrinsic (local) short term regulation

Local factors: acetylcholine

A
  • Role:
    1. Through nerve endings
      • Delibiration of ACh by direct stimulation of the vessel
      • Vasoconstriction
    2. Arriving from the lumen of blood vessel
      • Will act through endothelium
      • NO production ↑
      • Vasodilation
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8
Q

Intrinsic (local) short term regulation

Local factors: regulation through metabolites

A
  • Most important local autoregulative element
  • Mechanism of action:
    • metabolic activity:
      • ↑ O2-consumption
      • ↑ adenosine concentration
      • ↑ H+ concentration
      • ↑ CO2 concentration
      • ↑ K+ concentration
  • All of these factors stimulate endothelium (EDRF stimulation)
  • Response:
    • NO production ↑
    • Diffusion of NO into the smooth muscles
    • cGMP ↑ = relaxation
  • Lack of oxygen at tissue level (hypoxia) causes an automatic increase of the perfusion, resulting in better O2 supply
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9
Q

Intrinsic (local) long term regulation

A
  • Intensive and sustained work of an organ causes morphological changes that contribute to the better perfusion at the local level
  • Growth factors, enzyme induction etc.
  • Increased perfusion via angiogenesis (rearrangement and formation on new vessels)

Hyperemia:

  • Hyperemia: ↑ local perfusion
  1. Active hyperemia
    • Functional
    • If hyperemia is related to increased metabolic activity of the tissue
  2. Reactive hyperemia
    • Secondary increase of perfusion
    • I.e. compression of the artery of the limb reduces perfusion (pale), hyperemia happens, however, after compression is released
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