Biomedical Engineering Reference
In-Depth Information
Figure 5
. Conceptual scheme of the intrinsic cardiac nervous system (ICNS). Intracardiac
afferent neurons provide MECHANOsensitive and CHEMOsensitive input from atrial and
ventricular tissues to the intrinsic efferent adrenergic and cholinergic cardiac neurons. CNS =
central nervous system. For simplicity, the known sympathetic-parasympathetic interactions
and other known efferent intracardiac neurons are not shown. Bold lines represent the path-
ways of extrinsic cardiac neural feedback control. Thin lines represent intrinsic cardiac neural
pathways, the functional role of which remains to be established.
transplantation, it was observed that, although cardiac allografts are extrinsically
decentralized, they retain a viable intrinsic neuronal system (12).
An increasing body of evidence has accumulated (5,12) identifying a vari-
ety of neural cells residing in the heart and having distinct and significant effects
on cardiac performance. The premise that the heart is not merely a muscular
pump but is endowed with a level of self-organized neuroendocrine self-
regulation is very compelling. In broader terms, the concept of self-regulation is
based on the axiom that the heart is a regulatory system, integrating many com-
ponents, including endothelium-mediated control and afferent/efferent neural
mechanisms, and thereby provides feedback of its beat-to-beat performance as a
muscular pump (Figure 5). This view would suggest the existence of an intrinsic
neural network processor. In fact, the intrinsic neural network is organized such
that it functions as a neural center (heart brain) and can facilitate local control of
the disparate heart functions and integrate them such that their responses are not
merely parallel but tuned (optimized) to accommodate the varied influences on
the heart. This local processor might behave as a functional intrinsic cardiac
nervous system (ICNS). The conceptual understanding of the functional struc-
tures embodied by heart brain is schematized in Figure 8.
