CIRCULATION REGULATION AC Brown
page 1 A7c
INTRODUCTION
A. Define: Circulation regulation refers to the ability of the cardiovascular system to
adjust cardiac output and blood flow distribution to meet the needs of the body
B. Levels of Regulation
1. Inherent regulation: inherent responses of cardiac muscle and
peripheral blood vessels to local stimuli
2. CNS-Endocrine Reflex regulation: regulation involving CNS and
endocrine responses to
a. maintain systemic arterial pressure
b. maintain circulating blood volume
c. maintain blood gas concentrations (O2 & CO2)
3. Higher CNS-Endocrine control: more
complicated regulation, involving
a. integration with other organ systems
b. learned (conditioned) responses
c. emotional and similar responses
INHERENT REGULATION: CARDIAC MECHANISMS
A. Myocardial Contraction Energy-Diastolic Filling Relation
(Starling's Law of the Heart; sometimes called Frank-
Starling Law or pre-load effect)
STARLING'S LAW OF THE HEART: The larger the
ventricle just before contraction begins (end-diastolic
volume, EDV), the greater the energy of contraction
Reasons: (1) the greater efficiency of cardiac
contraction at larger volumes is a reflection of the
length-tension curve of cardiac muscle, and (2)
increased effectiveness of Ca ion on contraction
Note: When the ventricular volume becomes very large,
cardiac efficiency begins to decrease (decompensation)
Note: Starling's law can also be plotted as Cardiac Work against Ventricular Filling
Pressure or as Maximum Ventricular Pressure against Ventricular Volume. All three types
of plots are called Starling’s Curves or Contractility curves.
Contractility: curve of maximum ventricular pressure vs. ventricular volume or ventricular
filling pressure in systole
Distensibility: curve of ventricular pressure vs. ventricular volume in diastole
