Blood%20Pressure%20Regulation

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Blood Pressure Regulation
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General Definitions

• Blood Flow the volume of blood flowing through a
  vessel, organ or the entire circulation in a
  given period (ml/min)
• Blood Pressure the force exerted on a blood
  vessel by blood (mmHg)
• Resistance opposition to blood flow. A measure
  of friction within blood vessels
• Blood Viscosity thickness/ stickiness of blood
  itself, which will provide internal resistance to
  flow

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Important Points

• Blood flow is controlled by changes in pressure
• Blood will always flow from areas of high
  pressure to low pressure
• Average blood pressure
• Right 24/8 mmHg
• Left 120/80 mmHg
• Both sides eject the same volume of blood
  simultaneously

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Cardiac Output

• Cardiac Output (CO) the amount of blood pumped
  out by each ventricle in one minute
• CO SV x HR
• Stroke volume (SV) the volume of blood pumped
  out by each ventricle in each beat
• Heart rate (HR) the number of heart beats per
  minute
• (CO also EDV- ESV)

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Regulations of Stroke Volume

• 1. Preload amount that the ventricle is
  stretched when it is full of blood
• 2. Contractility the contractile force of
  cardiac cells
• 3. Afterload the pressure exerted by blood in
  the large arteries back on the heart

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Mean Arterial Pressure (MAP)

• The pressure that propels blood to the tissues
  throughout the cardiac cycle
• Two ways to determine MAP
• 1. MAP diastolic pressure 1/3 pulse pressure
• 2. MAP CO x TPR

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Total Peripheral Resistance

• The total resistance to blood flow in the body
• Affected mainly by
• Arteriolar radius
• Blood viscosity

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Blood Pressure Regulation

• Short-term mechanisms
• Neural controls
• Vasomotor center in brain
• Baroreceptor reflexes
• Chemoreceptor reflexes
• Chemical controls
• Sympathetic response (epinephrine)
• ANP- decreases blood volume
• ADH- conserves water
• Angiotensin II- vasoconstriction
• Inflammatory chemicals- vasodilation
• Alcohol- inhibits ADH

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Blood Pressure Regulation

• Long-term mechanisms
• Renal Regulation (kidney)
• Renin-Angiotensin mechanism
• Renin angiotensin

ADH
aldosterone