Dendrite
Dendrite Soma Axon Nucleus Node of Ranvier Axon Terminal Schwann cell Myelin sheath
Structure of a typical neuron

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Dendrites (from Greek dendron, “tree”) are the branched projections of a neuron that act to conduct the electrical stimulation received from other neural cells to the cell body, or soma, of the neuron from which the dendrites project. Electrical stimulation is transmitted onto dendrites by upstream neurons via synapses which are located at various points throughout the dendritic arbor. Dendrites play a critical role in integrating these synaptic inputs and in determining the extent to which action potentials are produced by the neuron. Image File history File links Neuron-no_labels. ... The soma is the bulbous end of a neuron, containing the nucleus. ... An axon or nerve fiber, is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neurons cell body or soma. ... The eukaryotic cell nucleus. ... Nodes of Ranvier are regularly spaced gaps in the myelin sheath around an axon or nerve fiber. ... Nodes of Ranvier are regularly spaced gaps in the myelin sheath around an axon or nerve fiber. ... Illustration of the major elements in a prototypical synapse. ... Named after the German physiologist Theodor Schwann, Schwann cells are a variety of neuroglia that mainly provide myelin insulation to axons in the peripheral nervous system of jawed vertebrates. ... In neuroscience, myelin is an electrically insulating fatty layer that surrounds the axons of many neurons, especially those in the peripheral nervous system. ... Image File history File links Neuro_logo. ... Drawing by Santiago Ramón y Cajal of neurons in the pigeon cerebellum. ... The soma is the bulbous end of a neuron, containing the nucleus. ... Synapses allow nerve cells to communicate with one another through axons and dendrites, converting electrical signals into chemical ones. ... Illustration of the major elements in a prototypical synapse. ... Schematic of an electrophysiological recording of an action potential showing the various phases which occur as the wave passes a point on a cell membrane. ...

Morphology

A human neocortical pyramidal neuron stained via Golgi technique. Notice the apical dendrite extending vertically above the soma and the numerous basal dendrites radiating laterally from the base of the cell body.

Dendrites are made up of dendritic segments which are named according to their relative position to the soma. For example, the initial segment of a dendrite that projects directly from a neuron cell body is called a “first order” segment. When a first order segment branches, its daughter segments are considered “second order” segments. Likewise, daughter segments of second order segments are called “third order” segments. This naming process continues until a dendrite segment ceases to branch. Non-branching dendrites are termed “terminal segments”. In addition, many dendrites contain dendritic spines, small mushroom like protrusions that offer isolated computational compartments on which axon terminals can create synapses. Image File history File links GolgiStainedPyramidalCell. ... Image File history File links GolgiStainedPyramidalCell. ... A pyramidal cell is a multipolar neuron located in the hippocampus and cerebral cortex. ... Drawing by Camillo Golgi of a hippocampus stained with the silver nitrate method Drawing of a Purkinje cell in the cerebellum cortex done by Santiago Ramón y Cajal, clearly demonstrating the power of Golgis staining method to reveal fine detail Golgis method is a nervous tissue staining... The soma is the bulbous end of a neuron, containing the nucleus. ... Close up of the dendrite of a striatal medium spiny neuron. ...

In general, whereas axons may span the length of nearly a meter, dendrites are more localised around the cell body. Two examples are spinal motor neurons with dendritic arbors of a few millimetres in diameter, and retinal amacrine cells, with arbors of only few hundred micrometers in diameter. Dendrites account for the bulk of the surface area of neurons, with as much as 98% of the neuronal phospholipid bilayer membrane devoted to the dendritic arbor. Additionally, excitatory and inhibitory synapses distribute themselves on the dendritic arbor such that excitatory synapses usually occupy more distal locations while inhibitory synapses are typically located more proximally. An axon, or nerve fiber, is a long slender projection of a nerve cell, or neuron, which conducts electrical impulses away from the neurons cell body or soma. ... In vertebrates, motoneurons (also called motor neurons) are efferent neurons that originate in the spinal cord and synapse with muscle fibers to facilitate muscle contraction and with muscle spindles to modify proprioceptive sensitivity. ... Amacrine cell Retinal cell interneuron interacting at the Inner Plexiform Layer (IPL), the second synaptic retinal layer where bipolar cells and ganglion cells synapse. ... A micrometre (American spelling: micrometer, symbol µm) is an SI unit of length equal to one millionth of a metre, or about a tenth of the size of a droplet of mist or fog. ... A diagonal molecular slab from the DPPC lipid bilayer simulation1; color scheme: PO4 - green, N(CH3)3 - violet, water - blue, terminal CH3 - yellow, O - red, glycol C - brown, chain C - grey. ... Synapses allow nerve cells to communicate with one another through axons and dendrites, converting electrical signals into chemical ones. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ...

Dendritic morphology, the structural and physical architecture of the dendritic arbor, varies greatly across neuronal type. Dendrites of Purkinje cells, a dominant cell type in the cerebellum, extend from the soma to form a nearly two dimensional arborization. Purkinje cells are stacked in the cerebellum much like dominoes (i.e., with their dendritic arbors parallel to each other) allowing the afferent connections of parallel fibers to run orthogonally through the Purkinje cell dendrites. Pyramidal neurons, the most prevalent excitatory neuron in the cerebral cortex harbour two different classes of dendrites. The apical dendrites extend vertically from the apex of the pyramidally shaped soma and project toward the pial surface of the cerebral hemispheres. The basal dendrites of pyramidal neurons project laterally from the base of the soma. The giant pyramidal Betz cells possess perisomatic dendrites, which come from almost any part of the soma. The distinction between different dendrite classes is particularly important for pyramidal neurons as apical dendrites typically receive afferent input from distant sources such as the thalamus while the basal dendrites receive inputs from nearby cortical areas. The term morphology in biology refers to the outward appearance (shape, structure, colour, pattern) of an organism or taxon and its component parts. ... ... Figure 1a: A human brain, with the cerebellum in purple. ... Figure 1a: A human brain, with the cerebellum in purple. ... In nervous systems, afferent signals or nerve fibers carry information toward the brain. ... Parallel fibers arise from granule cells in the cerebellar cortex. ... In mathematics, orthogonal is synonymous with perpendicular when used as a simple adjective that is not part of any longer phrase with a standard definition. ... A pyramidal cell (or pyramidal neuron) is a multipolar neuron located in the hippocampus and cerebral cortex. ... Location of the cerebral cortex Slice of the cerebral cortex, ca. ... An apical dendrite is a dendrite that emerges from the apex of a pyramidal cell. ... [www. ... A basal dendrite is a dendrite that emerges from the base of a pyramidal cell. ... Betz cells are pyramidal cell neurons located within the fifth layer of the grey matter in the primary motor cortex. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Location of the cerebral cortex Slice of the cerebral cortex, ca. ...

A sketch of a cerebellar Purkinje cell drawn by Santiago Ramon y Cajal highlighting the dendrites' intricate branching pattern and two dimensional architecture.

Image File history File links PurkinjeCellCajal. ... Image File history File links PurkinjeCellCajal. ... Drawing of pigeon Purkinje cells (A) by Santiago Ramon y Cajal Purkinje cells are a class of GABAergic neuron located in the cerebellar cortex. ... Santiago Ramon y Cajal Santiago Ramón y Cajal (May 1, 1852 - October 17/18, 1934) was a famous Spanish histologist and father of neuroscience. ...

Electrical properties of dendrites

The structure and branching of a neuron's dendrites, as well as the availability and variation in voltage-gated ion conductances, strongly influences how it integrates the input from other neurons, particularly those that input only weakly. This integration is both "temporal" -- involving the summation of stimuli that arrive in rapid succession -- as well as "spatial" -- entailing the aggregation of excitatory and inhibitory inputs from separate branches. Voltage-gated ion channel is a ion channel that is specifically activated, or gated, by the surrounding potential difference near the channel (or near the cell, neuron or synapse). ...

Dendrites were once believed to merely convey stimulation passively. In this example voltage changes measured at the cell body result from activations of distal synapses propagating to the soma without the aid of voltage-gated ion channels. Passive cable theory describes how voltage changes at a particular location on a dendrite transmit this electrical signal through a system of converging dendrite segments of different diameters, lengths, and electrical properties. Based on passive cable theory one can track how changes in a neuron’s dendritic morphology changes the membrane voltage at the soma, and thus how variation in dendrite architectures affects the overall output characteristics of the neuron. International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ... Voltage-gated ion channel is a ion channel that is specifically activated, or gated, by the surrounding potential difference near the channel (or near the cell, neuron or synapse). ... // [edit] Overview Figure. ...

Although passive cable theory offers insights regarding input propagation along dendrite segments, it is important to remember that dendrite membranes are host to a cornucopia of proteins some of which may help amplify or attenuate synaptic input. Sodium, calcium, and potassium channels are all implicated in contributing to input modulation. It is possible that each of these ion species has a family of channel types each with its own biophysical characteristics relevant to synaptic input modulation. Such characteristics include the latency of channel opening, the electrical conductance of the ion pore, the activation voltage, and the activation duration. In this way, a weak input from a distal synapse can be amplified by sodium and calcium currents en route to the soma so that the effects of distal synapse are no less robust than those of a proximal synapse. A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Atomic mass 22. ... General Name, Symbol, Number calcium, Ca, 20 Chemical series alkaline earth metals Group, Period, Block 2, 4, s Appearance silvery white Atomic mass 40. ... General Name, Symbol, Number potassium, K, 19 Chemical series alkali metals Group, Period, Block 1, 4, s Appearance silvery white Atomic mass 39. ... “Multivalent” redirects here. ... Latency is the time a message takes to traverse a system. ... Electrical conductance is the reciprocal of electrical resistance. ...

One important feature of dendrites, endowed by their active voltage gated conductances, is their ability to send action potentials back into the dendritic arbor. Known as backpropagating action potentials, these signals depolarize the dendritic arbor and provide a crucial component toward synapse modulation and long-term potentiation. In addition, a train of backpropagating action potentials induced artificially at the soma induce a calcium action potential at the dendritic initiation zone in certain types of neurons. If this mechanism is of physiological importance must remain open. An example of long-term potentiation (LTP). ...

Dendrite development

Despite the critical role that dendrites play in the computational tendencies of neurons, very little is known about the process by which dendrites orient themselves in vivo and are compelled to create the intricate branching pattern unique to each specific neuronal class. It is likely that a complex array of extracellular and intracellular cues modulate dendrite development. Early candidates include: Sema3A, Notch, CREST, and Dasm1. Sema3A may act as a dendritic chemoattractant that aids cortical pyramidal neurons in orienting their apical dendrites to the pial surface. Notch acts as a neurotrophic factor in aiding dendrite growth and branching, while CREST may play an important role in regulating calcium dependent growth signals. Dasm1 (Dendrite arborization and synapse maturation 1) expression appears to be highly localized to dendrites and may have substantial influence on dendrite (but not axon) development. In vivo (Latin for (with)in the living). ... In cell biology, molecular biology and related fields, the word extracellular means outside the cell. It is used in contrast to intracellular (inside the cell). ... In cell biology, molecular biology and related fields, the word intracellular means inside the cell. It is used in contrast to extracellular (outside the cell). ... Neurotrophins are a family of molecules that encourage survival of nervous tissue. ...

See also

• Neuron
• Dendritic spine
• Axon
• Synapse
• Purkinje cell
• Pyramidal neuron

Drawing by Santiago Ramón y Cajal of neurons in the pigeon cerebellum. ... Close up of the dendrite of a striatal medium spiny neuron. ... An axon or nerve fiber, is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neurons cell body or soma. ... Illustration of the major elements in a prototypical synapse. ... Drawing of pigeon Purkinje cells (A) by Santiago Ramon y Cajal Purkinje cells are a class of GABAergic neuron located in the cerebellar cortex. ... A pyramidal cell is a multipolar neuron located in the hippocampus and cerebral cortex. ...

References

• Kandel ER, Schwartz JH, Jessell TM. Principles of Neural Science, 4th ed. McGraw-Hill, New York (2000). ISBN 0-8385-7701-6
• Koch C. Biophysics of Computation, Oxford University Press, Oxford (1999). ISBN 0-19-510491-9
• Stuart G, Spruston N, Hausser M. Dendrites, Oxford University Press, USA (2000). ISBN 0-19-850488-8

Eric Richard Kandel (born November 7, 1929) is a neuroscientist who won a Nobel Prize in the year 2000 for his research on the physiological basis of memory storage in neurons. ... Principles of Nerual Science cover First published in 1981, Principles of Neural Science is a neuroscience textbook edited by Eric R. Kandel, James Schwartz, and Thomas Jessell. ... Christof Koch (born November 13, 1956) is an American neuroscientist. ...

External links

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