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Structure of a typical neuron

Soma
Dendrite Soma Axon Nucleus Node of Ranvier Axon Terminal Schwann cell Myelin sheath

The soma (pl. somata or somas), or cyton or perikaryon (pl. perikarya), is the bulbous end of a neuron, containing the cell nucleus. The word soma is Greek, meaning "body"; the soma of a neuron is often called the "cell body". There are many different specialized types of neurons and the size of the soma can range from about 3 micrometres to over 1 millimetre for some of the largest neurons of invertebrates.

The cell nucleus is a key feature of the soma. The nucleus is the source of most of the RNA that is produced in neurons and most proteins are produced from mRNAs that do not travel far from the nucleus. This creates a challenge for supplying new proteins to axon endings that can be a meter or more away from the soma. Axons contain microtubule-associated motor proteins that transport protein-containing vesicles between the soma and the synapses at the axon terminals. Such transport of molecules towards and away from the soma maintains critical cell functions.

The survival of some sensory neurons depends on axon endings making contact with sources of survival factors that prevent apoptosis. The survival factors are neurotrophic factors, including molecules such as nerve growth factor (NGF). NGF interacts with receptors at axon terminals, and this produces a signal that must be transported up the length of the axon to the nucleus. A current theory of how such survival signals are sent from axon endings to the soma includes the idea that NGF receptors are endocytosed from the surface of axon tips and that such endocytotic vesicles are transported up the axon. [1]

[edit] External links

• Histology at OU 3_09 - "Slide 3 Spinal cord"

v • d • e Histology: nervous tissue (TA A14.2.00, GA 9.849) Neurons (grey matter) Parts soma axon (axon hillock, axon terminals, axoplasm, axolemma, neurofibril/neurofilament) dendrite (Nissl body, dendritic spine, apical dendrite, basal dendrite) Types bipolar · pseudounipolar · multipolar · pyramidal · Purkinje · granule Afferent nerve fiber/ Sensory nerve GSA · GVA · SSA · SVA fibers (Ia, Ib or Golgi, II or Aβ, III or Aδ or fast pain, IV or C or slow pain) Efferent nerve fiber/ Motor nerve GSE · GVE · SVE Upper motor neuron · Lower motor neuron (α motorneuron, γ motorneuron) Termination Synapses neuropil · synaptic vesicle Interneuron (Renshaw) · neuromuscular junction · electrical synapse Sensory receptors Meissner's corpuscle · Merkel nerve ending · Pacinian corpuscle · Ruffini ending · Muscle spindle · Free nerve ending · Olfactory receptor neuron · Photoreceptor cell · Hair cell · Taste bud Support Glial cells Astrocyte (Radial glia) · Oligodendrocyte · Ependymal cells (Tanycytes) · Microglia Myelination (white matter) CNS: Oligodendrocyte PNS: Schwann cell · Neurolemma · Nodes of Ranvier/Internode · Schmidt-Lanterman incisures Related connective tissues epineurium · perineurium · endoneurium · nerve fascicle · meninges Other Posterior (Root, Ganglion, Ramus) · Anterior (Root, Ramus) · rami communicantes (Gray, White) · Preganglionic fibers · Postganglionic fibers · Lemniscus · Funiculus · Fasciculus · Decussation · Commissure Projection fibers · Association fiber · Commissural fiber peripheral nervous system navs: anat/histo/physio/dev, noncongen PNS somatic/autonomic/congen/neoplasia, symptoms+signs/eponymous, proc

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