The simplest proto-cell (stem-cell) differentiates into a series of major cell types. The neurons of the neurosecretory system are one of these major groups. The neurosecretory family have the responsibility of communications within the organism for purposes of growth, metabolism, external and internal sensing and locomotion. The endocrine system, in conjunction with the vascular system, is used for low priority signaling over long distances. The paracrine system is used for low priority signaling over short distances and relies largely upon diffusion within the local tissue. It is the neural system that has developed to support high priority, fast signaling over long distances.
The neurological community of the 20th Century settled on a paracrine method of signaling (#3A) as fundamental to neural signaling. Spaargarden, et. al. labeled this method endocrine because of its frequent imprecise usage within the community. The putative signaling agents were labeled neurotransmitters. This work will show that this is not the actual method of signaling used in the neural system and the chemicals labeled neurotransmitters play an entirely different (crucial) role.
By returning to the views held by many during the first half of the 20th Century, a much broader understanding of the operation of the neural system can be obtained. This understanding relies upon the Electrolytic Theory of the Neuron. Under this theory, signals within the neural system are carried by electrons. Electrons carry the information within neurons and through synapses connecting neurons.
All neurons fall into one of two architectural types. Those neurons that perform only signaling are described in modality #3B. The photoreceptor cells, and other sensory neurons, rely upon a secretory function to create their disks and hairs. These cells are placed under modality #3C because of this difference.
By expanding the varieties of neurons into categories #3B and #3C, it becomes possible to describe the variety of neurons found in any organism by their function and their location in the signaling chain. Under the label #3C are found the signal sensing neurons of stage 1. The photoreceptor cells are the only #3C neurons found in the visual system. Under the #3B label are found the signal processing, stages 2 & 4, neurons and the signal projection , stage 3, neurons of the visual system.
The specific cell types found under the above labels include:
Stage 1--Signal detection, Chapter 12.
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