18 Cv Regulation - CIRCULATION REGULATION page 1...

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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
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CIRCULATION REGULATION AC Brown page 2 A7c INHERENT REGULATION: CARDIAC MECHANISMS (continued) A. Myocardial Contraction Energy-Diastolic Filling Relation (continued) Utility 1.
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