What is "dendrite"

Dendrite \Den"drite\, n. [Gr. dendri`ths, fem. dendri^tis, of a tree, fr. de`ndron a tree: cf. F. dendrite.] (Min.) A stone or mineral on or in which are branching figures resembling shrubs or trees, produced by a foreign mineral, usually an oxide of manganese, as in the moss agate; also, a crystallized mineral having an arborescent form, e. g., gold or silver; an arborization.

mid-18c., from Greek dendrites "of or pertaining to a tree," from dendron "tree" (see dendro-). The mineral so called for its markings.

n. 1 (context cytology English) A slender projection of a nerve cell which conducts nerve impulses from a synapse to the body of the cell; a dendron. 2 (context cytology English) Slender cell process emanating from the cell bodies of dendritic cells and follicular dendritic cells of the immune system. 3 (context crystallography metallurgy English) tree-like structure of crystals growing as material crystallizes 4 A hermit who lived in a tree

n. short fiber that conducts toward the cell body of the neuron

Dendrites (from Greek δένδρον déndron, "tree") (also dendron) are the branched projections of a neuron that act to propagate the electrochemical 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 (usually their axons) via synapses which are located at various points throughout the dendritic tree. Dendrites play a critical role in integrating these synaptic inputs and in determining the extent to which action potentials are produced by the neuron.

Dendrites are one of two types of protoplasmic protrusions that extrude from the cell body of a neuron, the other type being an axon. Axons can be distinguished from dendrites by several features including shape, length, and function. Dendrites often taper off in shape and are shorter, while axons tend to maintain a constant radius and be relatively long. Typically, axons transmit electrochemical signals and dendrites receive the electrochemical signals. Although, some types of neurons in certain species lack axons and simply transmit signals via their dendrites. Dendrites provide an enlarged surface area to receive signals from the terminal buttons of other axons, and the axon also commonly divides at its far end into many branches, each of which ends in a nerve terminal, allowing for a chemical signal to pass simultaneously to many target cells. Synapses involving dendrites can be axodendritic, involving an axon signaling to a dendrite, or dendrodendritic, involving signaling between dendrites. Dendritic branching is also called "dendritic arborization" and "dendritic ramification." (The term "dendritic arborization" describes the branching of dendrites as looking like the many branches of a tree.)

When an electrochemical signal stimulates a neuron it causes changes in the electrical potential across the neuron’s plasma membrane. This change in the membrane potential will passively spread across the dendrite but becomes weaker with distance without an action potential. The action potential propagates the electrical activity along the membrane of the dendrite to the cell body and then afferently down the axon to the terminal buttons where it crosses the synapse.

Certain classes of dendrites contain small projections referred to as dendritic spines that increase receptive properties of dendrites to isolate signal specificity. Increased neural activity and the establishment of long-term potentiation at dendritic spines change the size, shape, and conduction. This ability for dendritic growth is thought to play a role in learning and memory formation. There can be as many as 15,000 spines per cell, each of which serves as a postsynaptic process for individual presynaptic axons. Dendritic branching can be extensive and in some cases is sufficient to receive as many as 100,000 inputs to a single neuron.

There are three main types of neurons; multipolar, bipolar, and unipolar. Multipolar neurons, such as the one shown in the image, are composed of one axon and many dendritic trees. Pyramidal cells are multipolar cortical neurons with pyramid shaped cell bodies and large dendrites called apical dendrites that extend to the surface of the cortex. Bipolar neurons have one axon and one dendritic tree at opposing ends of the cell body. Unipolar neurons have a stalk that extends from the cell body that separates into two branches with one containing the dendrites and the other with the terminal buttons. Unipolar dendrites are used to detect sensory stimuli such as touch or temperature.

The morphology of dendrites such as branch density and grouping patterns are highly correlated to the function of the neuron. Malformation of dendrites is also tightly correlated to impaired nervous system function.

In mathematics, a dendrite is a certain type of topological space that may be characterized either as a locally connected dendroid or equivalently as a locally connected continuum that contains no simple closed curves.

Dendrites may be used to model certain types of Julia set. For example, if 0 is pre-periodic, but not periodic, under the function f(z) = z + c, then the Julia set of f is a dendrite.

Dendrite is a contact adhesive and rubber cement brand marketed in India and South Asia, mainly in Eastern India, Bangladesh and Bhutan.

A crystal dendrite is a crystal that develops with a typical multi-branching tree-like form. Dendritic crystal growth is very common and illustrated by snowflake formation and frost patterns on a window. Dendritic crystallization forms a natural fractal pattern. Dendritic crystals can grow into a supercooled pure liquid or form from growth instabilities that occur when the growth rate is limited by the rate of diffusion of solute atoms to the interface. In the latter case, there must be a concentration gradient from the supersaturated value in the solution to the concentration in equilibrium with the crystal at the surface. Any protuberance that develops is accompanied by a steeper concentration gradients at its tip. This increases the diffusion rate to the tip. In opposition to this is the action of the surface tension tending to flatten the protuberance and setting up a flux of solute atoms from the protuberance out to the sides. However, overall, the protuberance becomes amplified. This process occurs again and again until a dendrite is produced.

The term "dendrite" comes from the Greek word dendron, which means "tree".

A dendrite in metallurgy is a characteristic tree-like structure of crystals growing as molten metal freezes, the shape produced by faster growth along energetically favourable crystallographic directions. This dendritic growth has large consequences in regard to material properties.

Dendrites form in unary (one-component) systems as well as multi-component systems. The requirement is that the liquid (the molten material) be undercooled, aka supercooled, below the freezing point of the solid. Initially, a spherical solid nucleus grows in the undercooled melt. As the sphere grows, the spherical morphology becomes unstable and its shape becomes perturbed. The solid shape begins to express the preferred growth directions of the crystal. This growth direction may be due to anisotropy in the surface energy of the solid–liquid interface, or to the ease of attachment of atoms to the interface on different crystallographic planes, or both (for an example of the latter, see hopper crystal). In metallic systems, interface attachment kinetics is usually negligible (for non-negligible cases, see dendrite (crystal)). In metallic systems, the solid then attempts to minimize the area of those surfaces with the highest surface energy. The dendrite thus exhibits a sharper and sharper tip as it grows. If the anisotropy is large enough, the dendrite may present a faceted morphology. The microstructural length scale is determined by the interplay or balance between the surface energy and the temperature gradient (which drives the heat/solute diffusion) in the liquid at the interface.

As solidification proceeds, an increasing number of atoms lose their kinetic energy, making the process exothermic. For a pure material, latent heat is released at the solid–liquid interface so that the temperature remains constant until the melt has completely solidified. The growth rate of the resultant crystalline substance will depend on how fast this latent heat can be conducted away. A dendrite growing in an undercooled melt can be approximated as a parabolic needle-like crystal that grows in a shape-preserving manner at constant velocity. Nucleation and growth determine the grain size in equiaxed solidification while the competition between adjacent dendrites decides the primary spacing in columnar growth. Generally, if the melt is cooled slowly, nucleation of new crystals will be less than at large undercooling. The dendritic growth will result in dendrites of a large size. Conversely, a rapid cooling cycle with a large undercooling will increase the number of nuclei and thus reduce the size of the resulting dendrites (and often lead to small grains).

Smaller dendrites generally lead to higher ductility of the product. One application where dendritic growth and resulting material properties can be seen is the process of welding. The dendrites are also common in cast products, where they may become visible by etching of a polished specimen.

As dendrites develop further into the liquid metal, they get hotter because they continue to extract heat. If they get too hot, they will remelt. This remelting of the dendrites is called recalescence.

Dendrites also form during the freezing of many nonmetallic substances such as ice.

Dendrites usually form under non-equilibrium conditions.

A common dendritic metal material is nickel carbonyl, where the particles have a classical "spiky" morphology.

An application of dendritic growth in directional solidification is gas engine turbine blades which are used at high temperatures and must handle high stresses along the major axes. At high temperatures, grain boundaries are weaker than grains. In order to minimize the effect on properties, grain boundaries are aligned parallel to the dendrites. The first alloy used in this application was a nickel-based alloy (MAR M-200) with 12.5% tungsten, which accumulated in the dendrites during solidification. This resulted in blades with high strength and creep resistance extending along the length of the casting giving improved properties compared to the traditionally-cast equivalent.

The word dendrite derives from the Greek word "dendron" meaning "tree".

A dendrite is a branched projection of a neuron.

Dendrite may also refer to:

• dendrite (non-neuronal), branching projections of certain skin cells and immune cells
• dendrite (metal), a characteristic tree-like structure of crystals growing as molten metal freezes
• dendrite (mathematics), a locally connected continuum that contains no simple closed curves
• dendrite (crystal), a crystal that develops with a typical multi-branching tree-like form
• Dendrite (adhesive), a brand of contact cement from India and South Asia

A dendrite is a branching projection of the cytoplasm of a cell. While the term is most commonly used to refer to the branching projections of neurons, it can also be used to refer to features of other types of cells that, while having a similar appearance, are actually quite distinct structures.

Non-neuronal cells that have dendrites:

• Dendritic cells, part of the mammalian immune system
• Melanocytes, pigment-producing cells located in the skin
• Merkel cells, receptor-cells in the skin associated with the sense of touch