Sixth Annual Peter A. Rechnitzer Lecture

WHY DO WE REQUIRE A SECOND HEART DURING EXERCISE?


RowellLoring B. Rowell, PhD

University of Washington School of Medicine
Seattle, Washington


Monday, May 15, 2000

Dr. L.B. Rowell is Professor Emeritus of Physiology and Biophysics and Adjunct Professor of Medicine at the University of Washington School of Medicine in Seattle, Washington. He has made outstanding contributions to understanding the integrative aspects of cardiovascular control in humans. Responses to various system perturbations that include posture and dynamic exercise have occupied his interests. These two stresses provide the necessary models to examine the important features of cardiovascular control both neural and humoral at the whole body level. His book "Human Cardiovascular Control" is a landmark text that brings together these ideas and is suitable for teaching integrative cardiovascular physiology. The original articles that make up the fabric of this book have been assembled in a superb fashion and have made it the most authoritative and readable repository of information in this area of physiology. Dr. Rowell's ideas on these topics remain at the centre of thought in integrative cardiovascular controls.

WHY DO WE REQUIRE A SECOND HEART DURING EXERCISE?

ABSTRACT: Dr. Rowell's talk will address the problem of maintaining central venous pressure in exercise. Several so called "pumps" can displace blood volume back to the heart: respiratory and abdominal muscles, and muscles of the limbs. The limb muscles are most important and the features that make them so effective as pumps are presented. It is argued that by contracting, these muscles can actually raise their own blood flow; this can happen even without help from the first heart the left ventricle. The need for a "second heart" is not obvious until we try to raise cardiac output without one. These attempts fail owing to physical properties of the peripheral circulation. The final message is that we need both a second heart and a neural control of blood vessels in order to maintain ventricular filling pressures during exercise.

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