The Role of Rods and Cones in Vision

Overview of Photoreceptors

• Photoreceptors: Specialized receptors in the retina that detect light.
• Types:
  • Rods
  • Cones

Structure and Function

• Retinal Pigment Epithelium:
  • Located at the back of the eye.
  • Absorbs light using melanin.
  • Causes graded potential in rods and cones.

Rods

• Shape: Named for their rod-like shape.
• Number: More numerous than cones.
• Function:
  • Operate in dim light (e.g., nighttime, dark rooms).
  • Cannot discriminate color (vision is in shades of gray).
• Image Processing:
  • Many rods feed into a few bipolar cells, which then feed into a single ganglion cell.
  • Produces a fuzzy, indistinct image due to averaging of stimuli.

Cones

• Shape: Named for their cone-like shape.
• Number: Less numerous than rods.
• Function:
  • Operate in bright light.
  • Can discriminate colors (red, green, blue).
  • Color vision results from combination and activation of different cones.
• Image Processing:
  • Each cone feeds into a single bipolar cell and a single ganglion cell.
  • Produces sharp, detailed, and high-resolution images.

Summary

• Rods provide vision in low-light conditions but lack color discrimination and produce less distinct images.
• Cones allow for color vision and high-resolution images under bright light conditions.