Difference between revisions of "Amacrine Cell"
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==Introduction== | ==Introduction== | ||
| − | + | [[Image:A2.png|thumb|right|240px|A type of amacrine cells, called '''AII''', reconstructed from EyeWire.]] | |
| − | + | Amacrine cells operate at the inner plexiform layer (IPL), the second synaptic retinal layer where [[Bipolar Cell|bipolar cells]] and [[Ganglion Cell|ganglion cells]] form synapses. There are about 40 different types of amacrine cells and are classified by the width of their field of connection, which layer(s) of the stratum in the IPL they are in, and by neurotransmitter type. No single type of amacrine cell predominates; the type with most frequency is observed only 13% of total population, and the remainders are distributed among many types of cell, each making up 5% or less of the total amacrine cell population. The average diameter of dendritic field for each type varies over 34 to 400 microns, and their overall shapes alone are enough to serve as criterion of classification. | |
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| + | There is no clear distinction between dendrites and axons in the processes of most of the amacrine cells, though they are often referred to as dendrites in general. | ||
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| + | Like horizontal cells, amacrine cells work laterally affecting the output from [[Bipolar Cell|bipolar cells]], however, their tasks are often more specialized. Each type of amacrine cell connects with a particular type of [[Bipolar Cell|bipolar cell]], and generally has a particular type of neurotransmitter. One such population, AII, 'piggybacks' rod bipolar cells onto the cone bipolar circuitry. It connects rod bipolar cell output with cone bipolar cell input, and from there the signal can travel to the respective [[Ganglion Cell|ganglion cells]]. | ||
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| + | Most are inhibitory using either GABA or glycine as neurotransmitters. | ||
==Physiology== | ==Physiology== | ||
Revision as of 21:47, 29 March 2012
Amacrine cells are interneurons in the retina. Amacrine cells are responsible for 70% of input to retinal ganglion cells. Bipolar cells, which are responsible for the other 30% of input to retinal ganglia, are regulated by amacrine cells.
Contents
Introduction
Amacrine cells operate at the inner plexiform layer (IPL), the second synaptic retinal layer where bipolar cells and ganglion cells form synapses. There are about 40 different types of amacrine cells and are classified by the width of their field of connection, which layer(s) of the stratum in the IPL they are in, and by neurotransmitter type. No single type of amacrine cell predominates; the type with most frequency is observed only 13% of total population, and the remainders are distributed among many types of cell, each making up 5% or less of the total amacrine cell population. The average diameter of dendritic field for each type varies over 34 to 400 microns, and their overall shapes alone are enough to serve as criterion of classification.
There is no clear distinction between dendrites and axons in the processes of most of the amacrine cells, though they are often referred to as dendrites in general.
Like horizontal cells, amacrine cells work laterally affecting the output from bipolar cells, however, their tasks are often more specialized. Each type of amacrine cell connects with a particular type of bipolar cell, and generally has a particular type of neurotransmitter. One such population, AII, 'piggybacks' rod bipolar cells onto the cone bipolar circuitry. It connects rod bipolar cell output with cone bipolar cell input, and from there the signal can travel to the respective ganglion cells.
Most are inhibitory using either GABA or glycine as neurotransmitters.
Physiology
Visual Response Properties
Cellular Biophysics
Anatomy
Location
Amacrine cells have their cell bodies located in the inner nuclear layer of the retina and have projections in the inner plexiform layer. Different subtypes of amacrine cells project differently in the inner plexiform layer, as shown in the figure to the right depicting different types of narrow-field amacrine cells.
Shape
Amacrine cells send projections from their cell bodies into the inner plexiform layer. These projections arborize differently for different subtypes of amacrine cells. Amacrine cells have these projections distributed rouhgly circularly in the inner plexiform layer, though some subtypes arborize asymmetrically. Most amacrine cells can be classified according to the diameter of their projection arborization: "narrow-field" cells have arbors less than 125 µm in diameter, "medium-field" cell arbors range from 125 to 400 µm in diameter, and "wide-field" cell arbors are larger than 400 µm.
