Rods
Rods (medicine)
Rods (/rɒdz/), in the field of medicine, are one of the two types of light-sensitive cells in the retina of the eye. They are responsible for vision at low light levels (scotopic vision). They do not mediate color vision, and have a low spatial acuity.
Etymology
The term "rod" comes from the Old English "rodd", meaning "a straight and slender piece of a substance". This is in reference to the rod-like shape of these cells.
Function
Rods are more sensitive to light than the other type of photoreceptor, cones, and allow for vision in dim lighting. However, they are not sensitive to color. The increased sensitivity of rods, compared to cones, is due to their high levels of a pigment called rhodopsin, which absorbs light.
Related Terms
- Photoreceptor cell: A type of neuron in the retina that converts light into signals that can be processed by the brain.
- Rhodopsin: A pigment found in the rods of the retina that is responsible for the formation of the photoreceptor cells.
- Scotopic vision: The vision of the eye under low-light levels, which is primarily mediated by rods.
- Cones: The other type of photoreceptor in the retina, responsible for color vision and high spatial acuity.
External links
- Medical encyclopedia article on Rods
- Wikipedia's article - Rods
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