rod cells are located in the retina in the eye.
rod cells are located in the retina in the eye.
where are rod cells located in the eye?
in the retina
there are two types of photoreceptor cells, rods and cones, which are sensitive to different aspects of light. rod cells are sensitive to the intensity of light over a wide frequency range, thus are responsible for black-and-white vision. rod cells are not present on the fovea, the area of the retina responsible for central vision, and are not as responsive as cone cells to spatial and temporal changes in light. there are, however, twenty times more rod cells than cone cells in the retina because the rod cells are present across a wider area. because of their wider distribution, rods are responsible for peripheral vision.
optics
the importance and versatility of depolarization within cells can be seen in the relationship between rod cells in the eye and their associated neurons. when rod cells are in the dark, they are depolarized. in the rod cells, this depolarization is maintained by ion channels that remain open due to the higher voltage of the rod cell in the depolarized state. the ion channels allow calcium and sodium to pass freely into the cell, maintaining the depolarized state. rod cells in the depolarized state constantly release neurotransmitters which in turn stimulate the nerves associated with rod cells. this cycle is broken when rod cells are exposed to light; the absorption of light by the rod cell causes the channels that had facilitated the entry of sodium and calcium into the rod cell to close. when these channels close, the rod cell produces less neurotransmitter, which is perceived by the brain as light. in the case of rod cells and neurons, depolarization actually prevents a signal from reaching the brain as opposed to stimulating the transmission of the signal.
depolarization