### Oscillation in biology: the "why?" and the "how?"

17 April 2015

Alan Garfinkel

Department of Medicine (Cardiology), UCLA

#### Abstract

20th century physiology and medicine were dominated by the doctrine of homeostasis. In its extreme form, homeostasis meant that physiological quantities like body temperature and hormone levels were controlled to constant equilibrium values. This is, of course, not true. Virtually all physiological quantities oscillate, often varying 100% in one cycle, and at many different time scales.

How can we generalize the ideas of regulation and interaction to these oscillatory processes? How can we have the "homeo" without the "stasis"?

Nonlinear dynamics gives us a powerful set of concepts with which to answer these questions. I will briefly develop the concepts necessary to define a limit cycle attractor, the model of a stable oscillation, and will then discuss the causes of oscillatory behavior from the mathematical point of view. I will give a few examples in physiology and pathophysiology of Hopf bifurcations, the birth of oscillatory processes.

The ubiquity of oscillatory processes in normal physiology raises the question why? The picture that is emerging is that the healthy body is an ensemble of oscillatory processes, orchestrated into distinct phases and rhythms through processes of synchronization (and anti-synchronization), I will present a general model for the phase regulation and synchronization of oscillatory processes, based in nonlinear dynamics.

current theory lunch schedule