Cells in retina

視桿細胞是視網膜中兩類感光細胞之一。光子撞擊視桿細胞，觸發神經遞質傳輸和電脈衝釋出，繼而傳送至中樞神經系統……它們無法感知顏色和細節，而由視錐細胞補充此功能。比起視錐細胞，視桿細胞對光更敏感，數量也更多。人眼包含約1.3億個視桿細胞和約700萬個視錐細胞。

Rod is one of two types of photoreceptive cells in the retina. Rod cells function as specialized neurons that convert visual stimuli in the form of photons into chemical and electrical stimuli that can be processed by the central nervous system...They do not perceive color and fine detail, tasks performed by the other major type of light-sensitive cell, the cone. Rod cells are much more sensitive to light than cones and are also much more numerous. The human eye contains about 130 million rods and about 7 million cones.

視錐細胞在視網膜中呈圓錐形凸出物，與彩色視覺和精細視覺有關。視錐細胞對暗光的敏感度遠小於眼睛的視桿細胞。視錐細胞大多集中在視網膜中央，其中包含中央凹（視網膜凹陷），其中不存在視桿細胞。相反，視網膜的外邊緣包含很少的視錐細胞和許多視桿細胞。當光撞擊視錐細胞時發生的化學變化最終會作為脈衝，經視神經纖維傳遞進大腦。

Cone, light-sensitive cell with a conical projection in the retina, associated with color vision and perception of fine detail. Far fewer than the eye’s rods, cones are less sensitive to dim light. Cones are mostly concentrated within the central retina, which contains the fovea (depression in the retina), where no rods are present. In contrast, the outer edges of the retina contain few cones and many rods. Chemical changes that occur when light strikes the cones are ultimately relayed as impulses to optic-nerve fibers that enter the brain.

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