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Structurally, cone cells have a cone-like shape at one end where an opsin specific to the type of cone absorbs incoming light. They are typically 40–50μm long, and their diameter varies from 0.5 to 4.0μm, being smallest and most tightly packed at the center of the eye at the fovea. The S cone spacing is slightly larger than the others.
Both postulated mechanisms depend on the protected environment provided by the invaginating synapses that horizontal cells make onto cones. [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.
Rod bipolar cells do not synapse directly on to ganglion cells. 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 ...
Bipolar cells in the retina are also unusual in that they do not fire impulses like the other cells found within the nervous system. Rather, they pass the information by graded signal changes. Bipolar cells convey impulses from photoreceptors ( rods and cones ) to ganglion cells, [ 6 ] which in turn transport the visual signals to the brain ...
The retina (from Latin rete 'net'; pl. retinae or retinas) is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs.The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then processes that image within the retina and sends nerve impulses along the optic nerve to the visual cortex to create visual perception.
Like cones, rod cells have a synaptic terminal, an inner segment, and an outer segment. The synaptic terminal forms a synapse with another neuron, usually a bipolar cell or a horizontal cell . The inner and outer segments are connected by a cilium , [ 3 ] which lines the distal segment. [ 4 ]
These unique features specialize the ribbon synapse to enable extremely fast, precise and sustained neurotransmission, which is critical for the perception of complex senses such as vision and hearing. Ribbon synapses are found in retinal photoreceptor cells, vestibular organ receptors, cochlear hair cells, retinal bipolar cells, and pinealocytes.
A neural pathway connects one part of the nervous system to another using bundles of axons called tracts. The optic tract that extends from the optic nerve is an example of a neural pathway because it connects the eye to the brain; additional pathways within the brain connect to the visual cortex.