Editing Neuron (section)

===Histology and internal structure===
[[File:Gyrus Dentatus 40x.jpg|thumb|[[Golgi stain|Golgi-stained]] neurons in human [[hippocampal]] tissue]]
[[File:SUM 110913 Cort Neurons 2.5d in vitro 488 Phalloidin no perm 4 cmle-2.png|thumb|Actin filaments in a mouse cortical neuron in culture]]

Numerous microscopic clumps called [[Nissl body|Nissl bodies]] (or Nissl substance) are seen when nerve cell bodies are stained with a basophilic ("base-loving") dye. These structures consist of [[Endoplasmic reticulum#Rough endoplasmic reticulum|rough endoplasmic reticulum]] and associated [[ribosomal RNA]]. Named after German psychiatrist and neuropathologist [[Franz Nissl]] (1860–1919), they are involved in protein synthesis and their prominence can be explained by the fact that nerve cells are very metabolically active. Basophilic dyes such as [[aniline]] or (weakly) [[hematoxylin]]<ref>{{cite book|title=State Hospitals Bulletin|url={{google books |plainurl=y |id=Wp8CAAAAYAAJ|page=378}}|year=1897|publisher=State Commission in Lunacy.|page=378}}</ref> highlight negatively charged components, and so bind to the phosphate backbone of the ribosomal RNA.

The cell body of a neuron is supported by a complex mesh of structural proteins called [[neurofilament]]s, which together with [[neurotubule]]s (neuronal microtubules) are assembled into larger neurofibrils.<ref name="Webster">{{cite web |title=Medical Definition of Neurotubules |url=https://www.merriam-webster.com/medical/neurotubules |website=www.merriam-webster.com}}</ref> Some neurons also contain pigment granules, such as [[neuromelanin]] (a brownish-black pigment that is byproduct of synthesis of [[catecholamine]]s), and [[lipofuscin]] (a yellowish-brown pigment), both of which accumulate with age.<ref>{{cite journal | vauthors = Zecca L, Gallorini M, Schünemann V, Trautwein AX, Gerlach M, Riederer P, Vezzoni P, Tampellini D | title = Iron, neuromelanin and ferritin content in the substantia nigra of normal subjects at different ages: consequences for iron storage and neurodegenerative processes | journal = Journal of Neurochemistry | volume = 76 | issue = 6 | pages = 1766–73 | date = March 2001 | pmid = 11259494 | doi = 10.1046/j.1471-4159.2001.00186.x | s2cid = 31301135 }}</ref><ref>{{cite journal | vauthors = Herrero MT, Hirsch EC, Kastner A, Luquin MR, Javoy-Agid F, Gonzalo LM, Obeso JA, Agid Y | title = Neuromelanin accumulation with age in catecholaminergic neurons from Macaca fascicularis brainstem | journal = Developmental Neuroscience | volume = 15 | issue = 1 | pages = 37–48 | date = 1993 | pmid = 7505739 | doi = 10.1159/000111315 }}</ref><ref>{{cite journal | vauthors = Brunk UT, Terman A | title = Lipofuscin: mechanisms of age-related accumulation and influence on cell function | journal = Free Radical Biology & Medicine | volume = 33 | issue = 5 | pages = 611–9 | date = September 2002 | pmid = 12208347 | doi = 10.1016/s0891-5849(02)00959-0 }}</ref> Other structural proteins that are important for neuronal function are [[actin]] and the [[tubulin]] of [[microtubule]]s. [[Class III β-tubulin]] is found almost exclusively in neurons. Actin is predominately found at the tips of axons and dendrites during neuronal development. There the actin dynamics can be modulated via an interplay with microtubule.<ref>{{cite journal | vauthors = Zhao B, Meka DP, Schellenberg R, König T, Schwanke B, Kobler O, Windhorst S, Kreutz MR, Mikhaylova M, Calderon de Anda F | title = Microtubules Modulate F-actin Dynamics during Neuronal Polarization | journal = Scientific Reports | volume = 7 | issue = 1 | pages = 9583 | date = August 2017 | pmid = 28851982 | pmc = 5575062 | doi = 10.1038/s41598-017-09832-8 | bibcode = 2017NatSR...7.9583Z }}</ref>

There are different internal structural characteristics between axons and dendrites. Typical axons seldom contain [[ribosomes]], except some in the initial segment. Dendrites contain granular endoplasmic reticulum or ribosomes, in diminishing amounts as the distance from the cell body increases.