Rods and Cones: Photoreceptors in the retina responsible for detecting light and converting it into neural signals.
Structure
Rods
Shape: Elongated cell body, rod-shaped
Components: Contain multiple "optic discs"
Protein: Rhodopsin
Cones
Shape: Cone-shaped
Components: Also contain "optic discs"
Protein: Photopsin
Function
Phototransduction Cascade: Both rods and cones trigger phototransduction when light hits their respective proteins (rhodopsin in rods, photopsin in cones).
Differences
Quantity
Rods: ~120 million per retina
Cones: ~6 million per retina
Location
Rods: Located in the periphery of the retina
Cones: Concentrated near the fovea
Vision Type
Rods: Responsible for black and white vision, night vision
Cones: Responsible for color vision
Sensitivity
Rods: Highly sensitive to light; 1,000 times more sensitive than cones
Cones: Less sensitive to light but essential for color detection
Types of Cones
Red Cones: 60% of all cones
Green Cones: 30% of all cones
Blue Cones: 10% of all cones
Recovery Time
Rods: Slow recovery time after activation
Cones: Fast recovery time
Practical Examples
Rods: Adjust slowly to darkness, causing the initial difficulty in seeing when moving from a well-lit area to a dark one
Cones: Enable quick adaptation to changes in illumination, like moving from bright outdoor light to indoor light without much difficulty