The article and the illustrations are good (although it is hard to read the text on some figures). A few minor edits are performed in the document itself. My general suggestions for improvement are listed below.
Short introductory definition
Is it really just morphology that defines neurons? Some neurons don’t have axons and some don’t have dendrites; some have neither, so you can’t use that criterion. Many glial cells have processes that resemble dendrites. Action potentials aren’t a good criterion for neurons either, since cells like retinal neurons (most) lack them. Is it the presence of synapses (input and/or output) that defines a neuron? If it is unclear, then this should perhaps be mentioned.
Glia should probably be mentioned somewhere in the article, since they outnumber neurons (by about 10x) but there are important differences. Regarding the claim that neurons “underlie the function of the nervous system”, it could also be noted that neuronal function also depends on properly functioning glia. Perhaps a good way to put it is that neurons are the central mediators of nervous system function while glia support neuronal function in many ways. Although the article is not about glia, but it seems that a good way to define neurons is to mention both as the cells that comprise the nervous system and describe what distinguishes neurons from glia.
The link to “action potential” takes the reader to an as-yet-unwritten article on “Neuronal Excitability”. I think there should be a separate article on the action potential itself. Arguably there should also be a figure of an action potential in this article, as it is the signature functional feature of most neurons.
This section should also mention that some neurons (e.g. rods) do not have axons, dendrites, or action potentials. This raises the question of what makes them neurons? Is it because they develop from the neural plate?
Note that the term “dendro dendritic synapse” is introduced here prior to any mention or definition of synapses.
Minor edits also applied to this section.
Before referring to “electrophysiological properties”, I think it would be useful to define explicitly that the principal function of neurons is to generate electrical signals (usually action potentials) and to communicate with other neurons or muscle cells via synapses.
A general description of synapses and at least passing mention of the principles of synaptic transmission (even if discussed more extensively in other entries) is needed before introducing other terms like long term potentiation and long term depression.
Passive electrical properties
The link to “gated channels” goes to an as-yet-unwritten article on gating currents, which is not quite the same thing.
Minor edits also applied to this section.
Active electrical properties
Minor edits applied to this section.
No suggestions for this section.
I suggest that this section be re-titled “Axonal action potential propagation” and that some mention is made of the function of myelination.
Someone else has added a parenthetical note that needs to be deleted (although it contains a good suggestion).
The last sentence is in conflict with the conclusions of Goldstein and Rall (1974).
Intrinsic electrical properties and subthreshold oscillations
Minor edits were applied to this section.
Nonuniformity in channels density
The last sentence needs more explanation (or a reference to further reading).
A little history
No suggestions for this section except that “Figs. xxx” needs to be completed.
This section needs revision. I didn’t really understand the part about subjectivity.
It seems to me that many readers might like to know more about the relationship between the neuron and diseases of the nervous system. Examples would include neurodegenerative diseases like Parkinson’s or even myelination disorders like multiple sclerosis.
Cajal paper title
I would like to comment on the title of the original Cajal paper reference, it's title was probably "Estructura de los centros nerviosos de las aves".
For Scholarpedia: Neuron, by Rodolfo Llinas
This is a colourful, informative article, exactly what the interested non-specialist expects to find in an encyclopedia. If anything, it might seem a bit heavy because of the terminology which is not always explained to the layman. Already on line 4: “ the membranous system bounds and defines different intracellular compartments and includes the outer cell membrane (the plasmalemma) that encompasses the global compartment defining cellularity itself.” Personally, I would need some explaning. But then, the reader might well find somewhere else in Scholarpedia a definition of “intracellular compartments”, of “plasmalemma” or of “cellularity”.
The illustrations are appetizing and well chosen.
The text, obviously, cannot deal exhaustively with the enormous amount of knowledge accumulated over the last hundred and more years on this central topic of neural science. It would be unfair to call it incomplete because here and there it deals only summarily with one or the other aspect of neuron physiology, anatomy or biochemistry. To me the aspects it deals with are well chosen and central.
Nobody will be offended if I make some minor observations. In the chapter on Passive electrical properties, line 2: I think it should be milieu, not melieu. Line 4: an electric field and a voltage difference: Isn’t that the same thing? Chapter on Axonal Spike: to call the telodendrion the distal dendrite is dangerous, to say the least, because a dendrite it is not and the reader might get confused, especially if he did not learn ancient Greek at school. “Terminal ramification” would be better. Toward the end of Intrinsic Electrical Properties: “bellow 1 Hz” is rather funny. Non Uniformity in Channels Density, line 3, an example of rather off-putting jargon: “voltage, ligand, second messenger and metabotropic conductances supported by specialized ionic plasma membrane bound channels”. A little History: line 5. I am not sure that the neurons that send fibers to the glands should be called motor neurons. Line 9: gangliosen zellen sounds wrong, but then Purkinje was Czech by birth. Later the standard expression was “Ganglienzellen”. After Thoughts: I think the last lines are strictly an outcome of Rodolfo’s subjectivity!