Pálcikasejtek

Pálcikasejtek, also known as rod cells or rods, are photoreceptor cells in the retina of the eye. They are responsible for vision in low light conditions and do not contribute to color perception. Rods are highly sensitive to light and can detect a single photon. They contain a pigment called rhodopsin, which is a light-sensitive molecule that undergoes a conformational change when exposed to light. This change triggers a cascade of events that ultimately leads to a signal being sent to the brain, allowing us to see in dim light.

Rods are more numerous than cones, another type of photoreceptor cell, and are distributed throughout the retina, with a higher concentration in the periphery. This distribution explains why our peripheral vision is better in low light than our central vision. Unlike cones, which are concentrated in the fovea, the central part of the retina responsible for sharp, detailed vision, rods are less concentrated there. This is why we often have to look slightly away from a faint object to see it clearly in dim light, a phenomenon known as the rod-based "night vision" effect.

The number of rods in the human retina is estimated to be around 120 million. They are essential for tasks such as navigating in the dark, detecting movement in low light, and seeing in twilight conditions. Damage or degeneration of rod cells can lead to various vision impairments, including nyctalopia, or night blindness.