Control of Circulation and Arterial Pressure

1
Control of Circulationand Arterial Pressure
Chapter 6

• Marijn Rolf

2
Introduction
3
Outline

• Heart
• Autoregulation (Frank-Starling principle)
• Central Nerve System
• Organs
• Autoregulation
• Central Nerve System
• Complete Model Description

4
Heart Autoregulation

• Frank-Starling in short
• ? venous return ? cardiac output ?

5
Heart Autoregulation

• Frank-Starling principle 1
• With constant afterload the RV end-systolic
  volume is independent of the end-diastolic
  volume.

? venous return ? RV output ?
6
Heart Autoregulation

• Frank-Starling principle 2
• The afterload of the RV is independent of the LA
  preload. The lungs compensate by using more
  capillaries.
• So
• ? RV output ? LV filling ?

7
Heart Autoregulation

• Side effect of Frank-Starling
• A higher pressure in the RA influences the
  depolarisation rate of the SA-node, resulting in
  an increased heartrate.
• So
• ? venous pressure ? heart rate ?

8
Heart Central Nerve System

• Sympathetic nervesventriclesincreases heart
  rate and muscle contractility
• Parasympathic nerves (vagi)SA- and AV-node,
  atriadecreases heart rate

9
Heart Central Nerve System

• Control loop is closed by baroreceptors on large
  arteries.Rising arterial pressure excites the
  baroreceptors, followed by a decrease in
  sympathetic activity.

10
Heart

• Model description
• CO HR SV HR Kc Pv

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Organs - Autoregulation

• Depends on the organs metabolic needs.
• Arteriolar vasodilation is caused by
• Decreased O2 concentration
• Increased CO2
• Adenosine release (waste product of ATP)

12
Organs Central Nerve System

• Sympathetic activity (except in the brain)causes
  arteriolar vasoconstriction regulating mean
  arterial blood pressure

13
Organs
14
Organs

• Model

15
Organs

• Model description
• CO (Pa-Pv)/Rper ?Pv -Ca/Cv ?Pa
• ?
• ?Pa Cv/(Cv Ca)Rper?CO
• ?Pv Ca/(Cv Ca)Rper?CO

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Complete Model

• Heart
• Organs

• CO HR SV HR Kc Pv
• ?Pv Ca/(Cv Ca)Rper?CO
• Pv Pm ? Pv

CO PmHRKc
1HRKcRperCa/(CaCv)
17
Reference

• Cardiovascular Physiology Concepts
• Richard E. Klabunde, Ph.D.
• http//www.cvphysiology.com