CHAPTER 15 



The control of the function of the heart 



STANLEY J . S A R N O F F 

 JERE H. MITCHELL 



Laboratory of Cardiovascular Physiology, 

 Xational Heart Institute, Bethesda, Maryland 



CHAPTER CONTENTS 



Performance Characteristics in the Isolated Heart (Intrinsic 

 Mechanisms) 

 The Ventricle 



Heterometric autoregulation 

 Homeometric autoregulation 



Influence of oxygen availability on ventricular performance 

 The Atrium 



Heterometric autoregulation 



Effect of atrial systole on LVED pressure and fiber length 

 Mitral valve closure 

 Neuronal Effects on the Performance Characteristics of the 

 Heart (Extrinsic Influences) 

 Influence of Cardiac Sympathetic Nerve Stimulation on the 

 Ventricle 

 Contractility 



End diastolic pressure-length relation 

 Synchronicity of ventricular contraction 

 Influence of Cardiac Sympathetic Nerve Stimulation on the 



Atrium 

 Influence of Efferent Vagal Nerve Stimulation on the 



Ventricle 

 Influence of Efferent Vagal Nerve Stimulation on the Atrium 

 Effect of Autonomic Nerve Stimulation on the Atrial Trans- 

 port Function (Relation Between Mean LA Pressure 

 and LVED Pressure) 

 Efl'ect of Autonomic Nerve Stimulation on Closure of the 



Mitral Valve 

 Summary of Effects of Cardiac Autonomic Nerve Stimulation 

 The Nervous Control of the Frank-Starling Mechanism: 

 Principles of the Innervated Heart 

 Influence of the Carotid Sinus on the Performance Charac- 

 teristics of the Heart 

 Carotido- Ventricular Reflex 

 Carotido-Atrial Reflexes 



The carotido-vago-atrial reflex 

 The carotido-sympatho-atrial reflex 

 Function of the Carotid Sinus 

 Reflex Changes in Heart Rate and Contractility 

 Interrelation of Intrinsic Mechanisms and Extrinsic In- 

 fluences 



Cardio\ascular Response to Exercise 



Changes in Cardiac Output and AV Oxygen Difference 



Peripheral Vascular Control 

 The Architecture of Circulatory Regulation 



AN INCREASED UNDERSTANDING of the integrated func- 

 tion of an organism is predicated, at least in part, on 

 understanding the function of its component organs. A 

 determination of the extent to which an organ makes 

 intrinsic readjustments to \arying conditions, i.e., 

 autoregulates, is a desirable and helpful precursor to a 

 more refined analysis of the effects of extrinsic in- 

 fluences. 



"'Broadly speaking, there are two main avenues of approach 

 in the attempt to unravel the complicated processes which 

 determine the function of any individual organ. On the one 

 hand, we may study its reaction in the intact animal to com- 

 paratively small environmental changes — a method of in- 

 estimable value, since it is one which may readily be applied 

 to man; on the other hand, we may remove the organ and 

 study its reaction under grossly artificial conditions. In the 

 former case, we sacrifice simplicity and full control to a close 

 approximation to normality in environment; in the latter case, 

 we sacrifice normality in environment in order to obtain greater 

 simplicity and a higher degree of experimental control. The 

 former may be referred to as the analytic method of experi- 

 mentation, the latter as the synthetic. On the one hand, we 

 attempt to dissociate the medley of influences which share in 

 determining the normal function of the organ, and to relegate 

 to each its particular office in maintaining this normality; on 

 the other hand, we attempt to associate these influences in 

 such a degree and in such a manner as to bring the isolated 

 organ back to an environment and function comparable to 

 the normal." 



489 



