🌟 Cues

• Structure of the retina
• Rods vs. Cones
• Visual pathway
• Phototransduction
• Retinal adaptation

🗒️ Notes

Retina: The innermost layer of the eye, containing 55 types of cells and 70% of sensory receptors. It consists of 10 histological layers, but 4 layers are physiologically important: pigment cells, rods and cones, bipolar cells, and ganglion cells.

Rods vs. Cones:

• Rods: 120 million, located in the periphery, sensitive to low light, responsible for night vision, and cannot detect color.
• Cones: 6 million, concentrated in the fovea, responsible for color vision and high-acuity vision, functioning primarily in daylight.

Phototransduction: A process where light activates photoreceptors (rods and cones), leading to hyperpolarization and reduced glutamate release, initiating visual signals.

Visual Pathway: Photoreceptors → bipolar cells → ganglion cells → optic nerve → optic chiasma (nasal fibers cross) → optic tract → lateral geniculate body → visual cortex.

Retinal Adaptation:

• Dark Adaptation: Increased sensitivity of rods and cones in low light, taking 30 minutes for full rod adaptation.
• Light Adaptation: Decreased sensitivity in bright light, breakdown of photopigments, and increased visual acuity.

📝 Summary

The physiology of vision involves multiple layers of the retina and complex interactions between photoreceptors, bipolar cells, and ganglion cells. Rods are responsible for night vision, while cones manage color and sharp daytime vision. The visual pathway transmits signals from the retina to the brain’s visual cortex, and the retina adapts to varying light conditions through processes of dark and light adaptation. Phototransduction plays a key role in converting light into visual signals, while the retina’s structure enables detailed visual processing.