Regulation of Systemic Arterial Pressure

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Regulation of Systemic Arterial Pressure
Youngwoo Bae
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Introduction

• The major cardiovascular variable being
  regulated is the mean arterial pressure in the
• systemic circulation
• Therefore, maintaining it is a prerequisite for
  ensuring adequate blood flow
• MeanSystemicArterialPressure(MAP) CardiacOutput
  (CO)TotalPeripheralResistance(TPR)
• All changes in mean arterial pressure mush be
  the result of changes in cardiac output and/or
• total peripheral resistance.
• Mean arterial pressure will change only if the
  arithmetic product of cardiac output and total
• peripheral resistance changes

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• Steady state
• - Outflow(1L/min), Driving pressure(?Pstable)
• Dilating outflow tube 1 (analogous to exercise)
• - Outflow(gt1L/min), Driving pressure(?Pdecrease
  to new steady state (inflowoutflow))
• ? Showing Dependence of arterial blood pressure
  upon total arteriolar resistance

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• Increased resistance (tubes 2 to 4) Decrease
  resistance (tube 1)
• Total resistance (unchanged), The reservoir
  pressure (unchanged), Total outflow (unchanged)
• It is the total arteriolar resistance that
  influences systemic arterial blood pressure. The
  
• distribution of resistances among organs is
  irrelevant in this regard.

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MAP

• The relationship can be derived formally from
  the basic equation relating flow, pressure, and
• resistance
• F ?P/R
• Rearranging and substitute suitable terms
• MAP Right arterial pressure CO TPR
• MAP CO TPR (Right arterial pressure 0mmHg)
• Mean Pulmonary Arterial Pressure CO Total
  Pulmonary Vascular Resistance
• Providing a way to integrate almost all the
  information related to MAP
• Ex) mean pulmonary arterial presser ltlt mean
  systemic arterial pressure
• - CO (pulmonary) CO (systemic)
• - Resistance (pulmonary) ltlt Resistance
  (Systemic)

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MAP

• Summary of factors that determine systemic
  arterial pressure
• Short Term (baroreceptor reflexes) vs. Long Term

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Arterial Baroreceptors

• Common carotid arteries carotid sinus
  baroreceptor
• 
  aortic arch baroreceptor
• Its nerve endings are highly sensitive to
  stretch or
• distortion.
• Since the degree of wall stretching is directly
  related to
• the pressure within the artery, these serve as
  pressure
• receptors
• Afferent neurons travel from them to the
  brainstem and
• provide input to the neurons of cardiovascular
  control
• centers there

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Medullary Cardiovascular Center

• Medullary cardiovascular center
• Primary integrating center for the baroreceptor
• reflexexs that is consistituted with a diffuse
  network of
• highly interconnected neurons
• Inputs from various baroreceptors determines
  the action
• potential frequency from the center along
  neural
• pathways that terminate upon the cell bodies
  and
• dendrites of the vagus (parasympathetic)
  neurons to the
• heart and the sympathetic neurons to the heart,
  arterioles,
• and veins.
• Hormone reflexes angiotensin II, vasopressin

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Operation of the Arterial Baroreceptor Reflex

• Hemorrhage ? arterial pressure ? ? impulse ?
• - heart rate ?
• - ventricular contractility ?
• - arteriolar constriction ? (resistance ? CO
  ?)
• - venous constriction ?
• Baroreceptor reflex function
• - short-term regulator
• - arterial baroreceptor adapt to new pressure
  after few
• days

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Blood volume and long-term regulation of arterial
pressure