Received October 26, 2007
Revised October 31, 2007
Accepted after revision October 31, 2007

¹ University of Montreal

^* To whom correspondence should be addressed. E-mail: drewarmour{at}hotmail.com.

	Abstract

It is hypothetised that the heart possesses a nervous system intrinsic to it that represents the final relay station for the coordination of regional cardiac indices. This little brain on the heart is comprised of spatially distributed sensory (afferent), interconnecting (local circuit) and motor (adrenergic and cholinergic efferent) neurons that communicate with others in intrathoracic extracardiac ganglia, all under the tonic influence of central neuronal command and circulating catecholamines. Neurons residing from the level of the heart to the insular cortex form temporally dependent reflexes that control overlapping, spatially determined cardiac indices. The emergent properties that most of its components display depend primarily on sensory transduction of the cardiovascular milieu. It is further hypothesized that the stochastic nature of such neuronal interactions represents a stabilizing feature that matches cardiac output to normal corporal blood flow demands. Thus, with regards to cardiac disease states, one must consider not only cardiac myocyte dysfunction but also the fact that components within this neuroaxis may interact abnormally to alter myocyte function. This review emphasizes the stochastic behavior displayed by most peripheral cardiac neurons that appears to be a consequence of their predominant cardiac chemosensory inputs, as well as their complex functional interconnectivity. Despite our limited understanding of the whole, current data indicates that the emergent properties displayed by most neurons comprising the cardiac neuroaxis will have to be taken in consideration when contemplating targeting its individual components if predictable, long-term therapeutic benefits are to accrue.

Key Words: Autonomic nervous system, Cardiac arrhythmia