FACTOID # 21: 15% of Army recruits from South Dakota are Native American, which is roughly the same percentage for female Army recruits in the state.
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
   
 
WHAT'S NEW
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Giant retinal ganglion cells

Giant retinal ganglion cells were discovered in the human and macaque retina by Dacey et al. (2005). They gave them this name because their dendritic trees were the biggest ever recorded of retinal ganglion cells. Giant retinal ganglion cells contain a visual pigment, melanopsin, allowing them to respond directly to light. They also receive connections from rods and cones, allowing them to encode colour and spatial information. Dacey et al. found the giants’ receptive field sizes to be about three times the diameter of those of parasol ganglion cells. There are only about 3000 giant retinal ganglion cells in each retina, comprising about 0.2% of the total number of retinal ganglion cells. When a giant is responding directly to light, Dacey et al. found its spectral sensitivity function to be similar in shape to those of rods and cones, but with a peak at 482 nm, in between S cones and rods. Dacey et al. also found giants’ dynamic range to be 3-4 log units, far larger than any other photoreceptor type's and covering nearly the entire range of illuminations of natural daylight. Under naturalistic lighting conditions, responses to their rods and cones are superimposed on the melanopsin response of giant retinal ganglion cells. Giants encode colour via an S-Off, (L + M)-On opponency. Their spatial modulation transfer function is low-pass, with an upper limit of about 0.6 cycles per degree. Dacey et al. propose that the giants subserve circadian functions and pupillary diameter, and via the rod and cone inputs, help mediate conscious perception of irradiance. Binomial name Homo sapiens Linnaeus, 1758 Subspecies Homo sapiens idaltu (extinct) Homo sapiens sapiens Human beings define themselves in biological, social, and spiritual terms. ... Species see text The macaques form the genus Macaca of Old World monkeys. ... A ganglion cell (or sometimes called a gangliocyte) is a type of neuron located in the retina that receives visual information from photoreceptors via various intermediate cells such as bipolar cells, amacrine cells, and horizontal cells. ... Melanopsin is a photopigment found in the ganglion cells of the retina that is involved in the regulation of Circadian rhythms. ... Normalised absoption spectra of human rod (R) and cone (S,M,L) cells. ... Normalised absorption spectra of human cone (S,M,L) and rod (R) cells Cone cells, or cones, are cells in the retina which only function in relatively bright light. ... Color is an important part of the visual arts. ... Receptive fields are areas of the retina, producing a change in the firing of cells in the visual system. ... The circadian rhythm is a name given to the internal body clock that regulates the (roughly) 24 hour cycle of biological processes in animals and plants. ... Irradiance, in physics, is the density of radiant flux incident on a given area, typically measured as a unit of power per unit area (for example watts per square metre). ...


References

  • Dacey, D. M., Liao, H.-W., Peterson, B. B., Robinson, F. R., Smith, V. C., Pokorny, J., et al. (2005). Melanopsin-expressing ganglion cells in primate retina signal colour and irradiance and project to the LGN. Nature, 433, 749-754.

  Results from FactBites:
 
Ganglion cell - Wikipedia, the free encyclopedia (501 words)
A ganglion cell (or sometimes called a gangliocyte) is a type of neuron located in the retina that receives visual information from photoreceptors via various intermediate cells such as bipolar cells, amacrine cells, and horizontal cells.
These cells are also known as midget retinal ganglion cells, confusingly abbreviated to M, based on the small sizes of their dendritic trees and cell bodies.
These cells are also known as parasol retinal ganglion cells, confusingly abbreviated to P, based on the large sizes of their dendritic trees and cell bodies.
  More results at FactBites »

 
 

COMMENTARY     


Share your thoughts, questions and commentary here
Your name
Your comments

Want to know more?
Search encyclopedia, statistics and forums:

 


Press Releases |  Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m