Neuron


The neuron is the anatomical and functioinal unit of the nervous system. It is the anatomical unit because it is a cell and as such it is an integrated nd self-referring metabolic and genetic unit (a living system indeed). It is the functional unit because as a collector and as a distributor of influences it functions as a unit.

Anatomically and functionally the neuron is formed by a collector (dendrites and sometimes the cell body) united via a distributive element (the axon, and in some cases, also the cell body and main dendrites) capable of conducting propagated spikes to an effector area formed by the terminal branching of the axon. The functional state of the collector area depends both on its internal state (referring state) and on the state of activity of the effector areas synapsing on it. Correspondingly, the state of activity of the effector area of a neuron depends on the state of activity of its collector area and on the presynaptic and nonsynaptic interactions with other effector areas that may take place in the neuropil and in the immeadiate vicinity of the next collector areas. This is true even in the case of amacrines cells in which collector and effector areas may be intermingled. The distributive element determines where the effector exerts its influence. (NC 9, BC 18)


The nervous system is a closed network of lateral, parallel, sequential and recursively interacting neurons.

The closed organization of the nervous system is apparent in its changes of state. In fact, aperationally the nervous syatem is a closed network of interacting neurons such that a change in the state of relative activity of a group of neurons always leads to a change in the state of relative activitiy of other groups of neurons, either directly through synaptic action, or indirectly through the participation of some physical or chemical intervening element. Therefore, the organization of the nervous system as a finite neuronal network is defined by relations of closeness in the neuronal interactions generated in the network. Sensory and effector neurons, as they would be described by an observer who sees an organism in an environment, are not an exception to this because all sensory activity in an organism leads to activity in its effector surfaces, and all effector activity in turn leads to changes in its sensory surfaces. That at this point an observer should see environmental elements intervening between the effector and the sensory sufaces of the organism is irrelevant because the nervous system is defined as a network of neuronal interactions by the interactions of its component neurons regardless of any intervening elements. (CS 461)


This page was last updated on June 26, 1996, by Rob Sable.