Difference between axon and dendrite2/18/2023 There are, however, exceptions to these general rules of neuronal organization. There are some dendrites that also serve as output systems (see dendro dendritic synapses by G. The axon conducts propagating electrochemical signals termed action potentials (usually initiated at the axon hillock, green in Figure 2B) away from the soma. the output pole, called the axon (coined in 1896 by Rudolph Albert von Kolliker red in Figure 1), arises as a single structure from the soma (and occasionally from a dendrite).With invertebrate neurons the dendrites arise most commonly from the axon (see Figure 3). the receiving or input pole generally consists of extensively branching tree-like extensions of the soma membrane known as dendrites (coined in 1889 by William His from dendros (Greek) meaning tree) which arise in vertebrate neurons directly from the cell body (the body is also a receiving site in most neurons).The point being that neurons can have many types of branching or, in fact, no branches at all. These bald neurons may be found in present day forms as receptors cells in, for instance, the carotid glomus, in gustatory system in vertebrate tongue or as photoreceptors in the retina. Early in the evolution of CNS, and during development, such cells were devoid of any plasmalemmal extensions. In general terms neurons are viewed as having an input and an output pole. Polarization of a developing spinal motor neuron that accompanies the clustering of sodium channels near the axon hillock (red). Spinal motor neuron labeled with antibodies to sodium channels at the axon initial segment (green) and neurofilaments (red) ( reproduced with permission). Avian optic lobe neuron showing axon emerging from dendrite (Cajal). 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.Īssociated with the plasmalemma (but also with other intracellular elements) are transmembrane macromolecules that control the functionality of nerve cells (voltage and ligand activated ionic channels, ionic pumps, non-gated ‘leakage’ channels) and the machinery that keeps the cells alive by continuously taking up and replacing the molecular modules that constitute the cell’s functional matrix.įigure 2: A. The soma houses the cell nucleus and most of the genomic expression and synthetic machinery that elaborates the proteins, lipids, and sugars that constitute the neuronal cytoplasm and membranes. Neurons are generically characterized by a central cell body or soma that comes in different shapes.
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