Melanopsin

Melanopsin

Melanopsin (pronounced: mel-uh-NOP-sin) is a type of photopigment found in specialized photosensitive cells in the retina of the eye. It is known to play a key role in the regulation of circadian rhythms, pupillary light reflex, and other light-related functions.

Etymology

The term "Melanopsin" is derived from the Greek words "melas", meaning black, and "opsin", meaning sight or vision. It was first identified in the skin of the African clawed frog in 1998.

Function

Melanopsin is found in intrinsically photosensitive retinal ganglion cells (ipRGCs), which are a type of neuron in the retina of the eye. These cells respond to light without the need for input from rods or cones, the cells typically responsible for vision. When these cells detect light, they send signals to different parts of the brain to regulate various biological functions.

Role in Circadian Rhythms

One of the key roles of melanopsin is in the regulation of circadian rhythms. These are physical, mental, and behavioral changes that follow a daily cycle. They are influenced by light and darkness in an organism's environment. Melanopsin-containing cells in the retina send light information to the suprachiasmatic nucleus (SCN), the body's "master clock", which helps regulate sleep-wake cycles, hormone release, and other daily rhythms.

Role in Pupillary Light Reflex

Melanopsin also plays a role in the pupillary light reflex, the process by which the pupil of the eye adjusts in response to changes in light intensity. When the retina detects bright light, signals are sent to the brain to constrict the pupil and limit the amount of light entering the eye. Conversely, in low light conditions, the pupil dilates to allow more light in. Melanopsin-containing cells are particularly sensitive to blue light, which is why blue light can cause the pupils to constrict more than other types of light.

Related Terms

• Photopigment
• Photosensitive
• Retina
• Circadian rhythms
• Pupillary light reflex
• Intrinsically photosensitive retinal ganglion cells
• Rods
• Cones
• Suprachiasmatic nucleus
• Pupil

External links

• Medical encyclopedia article on Melanopsin
• Wikipedia's article - Melanopsin

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