8.2.1 Photoreceptors in the Eye

• What are photoreceptors and where are they located?

  Specialized sensory cells in the retina
• Photoreceptors convert light into electrical signals
• There are two main types of photoreceptors: rods and cones
• What is the sensitivity of rods compared to cones?

  High sensitivity
• Match the type of photoreceptor with its function:

  Rods ↔️ Night vision

  Cones ↔️ Color vision
• Rods are primarily located in the peripheral retina.
• Cones have high visual acuity
• What transmits the electrical signals from photoreceptors to the brain?

  Optic nerve
• What conditions are rods responsible for vision in?

  Dim light
• Cones require brighter light to perceive colors
• What is found in the outer segment of photoreceptors?

  Photopigments
• The inner segment of photoreceptors contains the cell's organelles
• Steps in the structure of a photoreceptor (from outer to inner)

  1️⃣ Outer segment with photopigments

  2️⃣ Inner segment with organelles

  3️⃣ Cell body

  4️⃣ Synaptic terminal
• What is the function of the synaptic terminal in photoreceptors?

  Transmit signals
• Rods contain the photopigment rhodopsin.
• Cones have folds of membrane containing opsins in their outer segment
• Why do rods contain many discs with rhodopsin in their outer segment?

  High sensitivity
• Match the type of photoreceptor with its associated photopigment:

  Rods ↔️ Rhodopsin

  Cones ↔️ Opsins
• Cones enable us to see colors in bright light.
• Rods have low visual acuity
• What are photoreceptors?

  Specialized sensory cells
• Rods have high sensitivity and are used for night vision
• Match the type of photoreceptor with its primary function:

  Rods ↔️ Night vision

  Cones ↔️ Color vision
• When light strikes photoreceptors, it triggers chemical reactions that produce electrical signals.
• Where are cones primarily located in the retina?

  Central fovea
• Cones have low sensitivity but high visual acuity
• What type of photoreceptor allows us to see fine details in bright light?

  Cones
• Rods are more sensitive to light than cones.
• Match the part of a photoreceptor with its description:

  Outer segment ↔️ Contains photopigments

  Inner segment ↔️ Contains cell organelles

  Synaptic terminal ↔️ Transmits signals
• What is the photopigment found in rods?

  Rhodopsin
• In rods, light activates rhodopsin, which then activates transducin
• Steps of phototransduction in rods

  1️⃣ Light strikes rhodopsin

  2️⃣ Transducin is activated

  3️⃣ PDE hydrolyzes cGMP

  4️⃣ Sodium channels close
• What are the three types of opsins in cones sensitive to?

  Red, green, blue light
• Cones require brighter light levels to initiate phototransduction
• What are the two types of photoreceptors in the retina?

  Rods and cones
• Rods are more sensitive to light than cones.
• Cones are responsible for color vision
• Where are rods primarily located in the retina?

  Peripheral retina
• Cones have high sensitivity to light.

  False
• Match the photoreceptor type with its primary location:

  Rods ↔️ Peripheral retina

  Cones ↔️ Central fovea