visual purple


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purple

 [pur´p'l]
1. a color between blue and red.
2. a substance of this color used as a dye or indicator.
visual purple rhodopsin.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

rho·dop·sin

(rō-dop'sin), [MIM*180380]
A purplish-red thermolabile protein, MW about 40,000, found in the external segments of the rods of the retina; consists of opsin combined with 11-cis retinal; it is bleached by the action of light, which converts it to opsin and all-trans-retinal, and is restored in the dark by rhodogenesis; the dominant protein in the plasma membrane of rod cells.
Synonym(s): visual purple
Farlex Partner Medical Dictionary © Farlex 2012

visual purple

n.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

rho·dop·sin

(rō-dop'sin)
A red thermolabile protein found in the rods of the retina; it is bleached by the action of light, which converts it to opsin and all-trans-retinal, and is restored in the dark by rhodogenesis; the dominant protein in the plasma membrane of rod cells.
Synonym(s): visual purple.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

visual purple

Rhodopsin. A light-sensitive pigment in the rods of the retina that is chemically changed on exposure to light and in the process stimulates production of a nerve impulse. Visual purple is reformed in the dark.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

rhodopsin 

Visual pigment contained in the outer segments of the rod cells of the retina and involved in scotopic vision. When light stimulates the retina, the chromophore of the pigment molecule '11-cis' retinal (which is vitamin A aldehyde) isomerizes to 'all-trans' retinal. This leads to other chemical transformations which carry on even in the absence of light. The first stage is prelumirhodopsin, then lumirhodopsin and finally metarhodopsin (of which there are two types). This last transformation may lead to the breakdown of the molecule into retinal and opsin. The molecule is regenerated by recombining retinal and opsin with some enzymes. The absorption spectrum of rhodopsin has a maximum around 498 nm. The isomerization from '11-cis' to 'all-trans' also gives rise to the process of transduction in which the membrane potential covering the pigment molecules in the outer segment changes towards a hyperpolarization of the cell. This is the first step in the nervous response to a light stimulation of the retina. Syn. visual purple (not used any more); erythropsin. See dark adaptation; bleaching; receptor potential; absorption spectrum; transduction.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann

rho·dop·sin

(rō-dop'sin) [MIM*180380]
A red thermolabile protein found in the rods of the retina.
Synonym(s): visual purple.
Medical Dictionary for the Dental Professions © Farlex 2012