Rod


Rod
/rod/, n.
a male given name, form of Roderick or Rodney.

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(as used in expressions)
Carew Rod

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      old English measure of distance equal to 16.5 feet (5.029 metres), with variations from 9 to 28 feet (2.743 to 8.534 metres) also being used. It was also called a perch or pole. The word rod derives from Old English rodd and is akin to Old Norse rudda (“club”). Etymologically rod is also akin to the Dutch rood which referred to a land area of 40 square rods, equal to one-quarter acre, or 10,890 square feet (1,012 square metres). It also denoted just one square rod, or 272.25 square feet (25.29 square metres). The rood also was a British linear unit, containing 660 feet (201.2 metres).

▪ retinal cell
      one of two types of photoreceptive cells in the retina of the eye in vertebrate animals. Rod cells function as specialized neurons that convert visual stimuli in the form of photons (particles of light) into chemical and electrical stimuli that can be processed by the central nervous system. Rod cells are stimulated by light over a wide range of intensities and are responsible for perceiving the size, shape, and brightness of visual images. They do not perceive colour and fine detail, tasks performed by the other major type of light-sensitive cell, the cone. Rod cells are much more sensitive to light than cones and are also much more numerous. The human eye contains about 130 million rods and about 7 million cones.

      Rod cells have an elongated structure and consist of four distinct regions: an outer segment, an inner segment, the cell body, and the synaptic region. The outer segment contains the phototransduction apparatus. It is composed of a series of closely packed membrane disks that contain the photoreceptor molecule rhodopsin. Genetic mutations in the rhodopsin molecule have been shown to produce certain forms of retinitis pigmentosa, an inherited degenerative disease of the retinal pigments. The synaptic region is the site where the rod cell relays its information to intermediate neurons in the retina. These neurons connect with ganglion neurons whose axons form the approximately one million fibres of the optic nerve.

      Rhodopsin is made up of a protein called opsin and a photosensitive chemical derived from vitamin A, -retinaldehyde. Photons of light entering the eye cause the 11-cis-retinaldehyde to undergo isomerization (a change in configuration), forming all-trans-retinaldehyde. This isomerization activates the opsin protein, which then interacts with and activates a small protein called transducin. The association of opsin with transducin couples the external stimulus of light to an internal biochemical pathway that ultimately alters the release of neurotransmitters from the synaptic region of the cell. This changes the firing of the intermediate retinal neurons and affects the electrical impulses sent along the optic nerve to the brain. Such a complicated relay system allows for some integration and fine-tuning of these signals.

      Rhodopsin molecules are broken down in sunlight or other bright viewing conditions. This breakdown prevents the overstimulation of the rod cells and makes them less sensitive to a bright environment. In dim light there is little breakdown of rhodopsin, and its persisting high concentration allows for better vision in a dark environment. Dark-adapted vision in humans is basically devoid of colour because it depends almost entirely on the functioning of rods. Compare cone cells.

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Universalium. 2010.

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  • Rod — may mean: *Rod (geometry), a straight and slender stick; a wand; a cylinder; hence, any slender bar *Rod cell, a cell found in the retina that is sensitive to light/dark (black/white) *Rod (length), an Imperial unit of length, also known as the… …   Wikipedia

  • rod — rȏd m <G rȍda, N mn ròdovi> DEFINICIJA 1. a. ono što je rođeno; porod, potomstvo, vrsta b. obitelj, obiteljska loza, soj c. rodbina, srodnici (ob. krvni, po ocu i majci) d. svojta [biti rod] 2. urod, plod, plodovi (voća, krumpira) 3. a.… …   Hrvatski jezični portal

  • Rod — bezeichnet: eine Längeneinheit, siehe Rute (Einheit) ein altdeutsches Wort (auch Rodt) für die Stelle einer Rodung zum Zwecke der Felderweiterung oder Siedlung einen Hot Rod, ein speziell getunter Oldtimer die Ausführung aus massivem Metall… …   Deutsch Wikipedia

  • rod — ROD, roade, s.n. 1. Nume generic dat produselor vegetale obţinute de la plantele cultivate, în special fructelor; fruct. ♢ loc. adj. Cu rod = roditor, fructifer. ♢ Compuse: rodul pământului = plantă erbacee veninoasă, cu frunze mari, late şi… …   Dicționar Român

  • rod — [rɔd US ra:d] n [: Old English; Origin: rodd] 1.) a long thin pole or bar steel/iron/wooden etc rod ▪ The walls are reinforced with steel rods. ▪ a measuring rod ↑basket, ↑net, ↑reel, ↑rod 2.) …   Dictionary of contemporary English

  • Rod — Saltar a navegación, búsqueda El término Rod puede tener diferentes significados: Unidad de medida anglosajona (Unidad longitud Rod) Rod (criptozoología y ufología), supuestos fenómenos o criaturas pseudocríptidas. Siglas de una serie de novelas… …   Wikipedia Español

  • rod — ► NOUN 1) a thin straight bar, especially of wood or metal. 2) a fishing rod. 3) a slender straight stick or shoot growing on or cut from a tree or bush. 4) (the rod) the use of a stick for caning or flogging. 5) Anatomy one of two types of light …   English terms dictionary

  • rod — [räd] n. [ME rodde < OE rodd, akin to ON rudda, club, prob. < IE base * rēt , *rōt , bar, beam > L retae, trees on a river bank] 1. a straight, slender shoot or stem cut from, or still part of, a bush or tree 2. Bible an offshoot or… …   English World dictionary

  • Rod — Rod, n. [The same word as rood. See {Rood}.] 1. A straight and slender stick; a wand; hence, any slender bar, as of wood or metal (applied to various purposes). Specifically: (a) An instrument of punishment or correction; figuratively,… …   The Collaborative International Dictionary of English

  • rôd — m 〈G rȍda, N mn ròdovi〉 1. {{001f}}a. {{001f}}ono što je rođeno; porod, potomstvo, vrsta b. {{001f}}obitelj, obiteljska loza, soj c. {{001f}}rodbina, srodnici (ob. krvni, po ocu i majci) d. {{001f}}svojta [biti ∼] 2. {{001f}}urod, plod, plodovi… …   Veliki rječnik hrvatskoga jezika


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