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Instead, rod bipolar cells synapse on to a Retina amacrine cell, which in turn excite cone ON bipolar cells (via gap junctions) and inhibit cone OFF bipolar cells (via glycine-mediated inhibitory synapses) thereby overtaking the cone pathway in order to send signals to ganglion cells at scotopic (low) ambient light conditions. [2]
In the anatomy of the eye, amacrine cells are interneurons in the retina. [1] They are named from Greek a– 'non' makr– 'long' and in– 'fiber', because of their short neuronal processes. Amacrine cells are inhibitory neurons which project their dendritic arbors onto the inner plexiform layer (IPL).
[4] [9] The first postulated mechanism is a very fast ephaptic mechanism that has no synaptic delay, making it one of the fastest inhibitory synapses known. [ 4 ] [ 10 ] [ 11 ] The second postulated mechanism is relatively slow with a time constant of about 200 ms and depends on ATP release via Pannexin 1 channels located on horizontal cell ...
In addition to responding directly to light, these cells may receive excitatory and inhibitory influences from rods and cones by way of synaptic connections in the retina. The axons from these ganglia innervate regions of the brain related to object recognition, including the superior colliculus and dorsal lateral geniculate nucleus .
A retinal ganglion cell (RGC) is a type of neuron located near the inner surface (the ganglion cell layer) of the retina of the eye.It receives visual information from photoreceptors via two intermediate neuron types: bipolar cells and retina amacrine cells.
In the nervous system, a synapse [1] is a structure that allows a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or a target effector cell. Synapses can be classified as either chemical or electrical, depending on the mechanism of signal transmission between neurons.
Asymmetric synapses are typically excitatory. Symmetric synapses in contrast have flattened or elongated vesicles, and do not contain a prominent postsynaptic density. Symmetric synapses are typically inhibitory. The synaptic cleft—also called synaptic gap—is a gap between the pre- and postsynaptic cells that is about 20 nm (0.02 μ) wide. [12]
Once at the synapse, synaptic vesicles are loaded with a neurotransmitter. Loading of transmitter is an active process requiring a neurotransmitter transporter and a proton pump ATPase that provides an electrochemical gradient. These transporters are selective for different classes of transmitters.