Compensatory mechanism – Counterregulatory mechanism

Compensatory mechanism

  • Renin-Angiotensin-Aldosterone-System (RAAS)
  • Neurohormonal response – RAAS
  • Endothelin release (contractility)
  • Cytokine release (Hypertrophy)
  • Inadequate stroke volume and CO –  (Epi and NoreEpi)
  • Ventricular remodeling
    • Continuous activation of neuro-hormonal responses (RAAS and SNS)
    • Hypertrophy of ventricular myocytes
    • Ventricles larger but less effective in pumping
    • Can cause life-threatening dysrhythmias and sudden cardiac death
  • Dilation
    • Enlargement of chambers of heart that occurs when pressure in left ventricle is elevated
    • Initially effective
    • Eventually this mechanism becomes inadequate and CO decreases
  • Hypertrophy
    • Increase in muscle mass and cardiac wall thickness
    • Initially effective
    • Over time leads to poor contractility, increased O2 needs, poor coronary artery circulation, and risk for ventricular dysrhythmias

Counterregulatory mechanism

  • Natriuretic peptides
    • Atrial natriuretic peptide (ANP),
      b-type natriuretic peptide (BNP)
    • Released in response to increased blood volume in heart
    • Causes diuresis, vasodilation, and lowered BP
    • Counteracts effects of SNS and RAAS
  • Nitric oxide (NO) and prostaglandin
    • Released from vascular endothelium in response to compensatory mechanisms
    • NO and prostaglandin relaxes arterial smooth muscle, resulting in vasodilation and decreased afterload

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