Blood Pressure

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Cardiovascular

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
    - Includes the RAAS system