USMLE

Blood Pressure

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Cardiovascular
  1. Cardiovascular Overview
  2. CO2 Transport
  3. Heart
  4. Cardiac Impulse
  5. Blood Pressure
  6. Arteries and Arterioles
  7. Veins and Venules
  8. Capillaries
  9. Circulation
  10. Blood
  11. Hemoglobin
  12. Blood Clotting
  • Topic Anchor: Blood Pressure 
    • Pressure experienced by blood inside the circulation
      • Fluid travels from high → low pressure, which drives circulation and perfusion
      • Highest pressure in aorta, lowest in veins
    • Blood pressure usually reported as pressure inside arteries
      • Systolic (SBP)
        • highest pressure in vessels
        • during contraction (systole) of ventricles
      • Diastolic (DBP)
        • lowest pressure in vessels
        • during relaxation (diastole) and filling of ventricles
      • Mean arterial pressure (MAP)
        • Average blood pressure throughout a cardiac cycle
        • Calculated as MAP = (SBP + 2*DBP)/3
    • Blood pressure depends on two factors
      • Blood pressure = cardiac output * vascular resistance
      • Cardiac output (CO)
        • Determines the amount of blood pumped into the circulation by the heart per unit time.
        • Calculated as CO = stroke volume x heart rate
      • Vascular Resistance (VR)
        • Resistance to blood flow determined by diameter of blood vessels
        • Controlled by vasoconstriction/dilation
        • Largest pressure drop across arterioles
          • Main source and determinant of vascular resistance
    • Regulation of blood pressure
      • Nervous Control acts quickly/fast
        • Baroreceptors in arteries detect changes in blood pressure, then signal brainstem to alter sympathetic and parasympathetic nervous system
      • Hormones act slowly