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Health effects of sunlight exposure. Exposing skin to the ultraviolet radiation in sunlight has both positive and negative health effects. On the positive side, exposure allows for the synthesis of vitamin D 3. Vitamin D has been suggested as having a wide range of positive health effects, which include strengthening bones [ 1] and possibly ...
Eye movements are used by a number of organisms (e.g. primates, rodents, flies, birds, fish, cats, crabs, octopus) to fixate, inspect and track visual objects of interests. A special type of eye movement, rapid eye movement, occurs during REM sleep . The eyes are the visual organs of the human body, and move using a system of six muscles.
A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The great biological importance of photoreceptors is that they convert light (visible electromagnetic radiation) into signals that can stimulate biological processes. To be more specific, photoreceptor proteins in ...
Cats tend to stop growing once they've reached 1 year old. A 12-month-old cat is equivalent in age to a 15-year-old human, according to PetMD. But some cats do continue to grow past the 12-month ...
The speed of movement during each saccade cannot be controlled; the eyes move as fast as they are able. [4] One reason for the saccadic movement of the human eye is that the central part of the retina —known as the fovea —which provides the high-resolution portion of vision is very small in humans, only about 1–2 degrees of vision, but it ...
Health threats from cosmic rays are the dangers posed by cosmic rays to astronauts on interplanetary missions or any missions that venture through the Van-Allen Belts or outside the Earth's magnetosphere. [ 1][ 2] They are one of the greatest barriers standing in the way of plans for interplanetary travel by crewed spacecraft, [ 3][ 4][ 5] but ...
Intermediate directions are controlled by simultaneous actions of multiple muscles. When one shifts the gaze horizontally, one eye will move laterally (toward the side) and the other will move medially (toward the midline). This may be neurally coordinated by the central nervous system, to make the eyes move together and almost involuntarily.
Cosmic ray visual phenomena, or light flashes ( LF ), also known as Astronaut's Eye, are spontaneous flashes of light visually perceived by some astronauts outside the magnetosphere of the Earth, such as during the Apollo program. While LF may be the result of actual photons of visible light being sensed by the retina, [ 1] the LF discussed ...