photorécepteurs

Photorécepteurs are specialized cells in the retina of the eye that are responsible for converting light into electrical signals. These signals are then transmitted to the brain, where they are interpreted as vision. There are two main types of photoreceptors in the human eye: rods and cones.

Rods are highly sensitive to light and are primarily responsible for vision in low-light conditions, also known as scotopic vision. They do not perceive color and provide black-and-white vision. Rods are more numerous than cones and are distributed throughout the retina, with a higher concentration in the peripheral regions.

Cones are less sensitive to light than rods and are responsible for color vision and sharp, detailed vision in bright light, known as photopic vision. There are three types of cones, each sensitive to different wavelengths of light: red, green, and blue. The brain combines the signals from these three types of cones to perceive the full spectrum of colors. Cones are concentrated in the fovea, the central part of the retina, which is responsible for our sharpest vision.

The process of phototransduction, by which light is converted into an electrical signal, occurs within the photoreceptor cells. When light strikes a photopigment molecule within the photoreceptor, it triggers a cascade of biochemical reactions that ultimately lead to a change in the cell's membrane potential. This electrical signal is then passed on to other neurons in the retina, which relay it to the brain via the optic nerve. Damage or degeneration of photoreceptors can lead to various visual impairments, including night blindness, color blindness, and even complete vision loss.