Rod and cone cells

Question 1

Where are the photoreceptors found?

Answer 1

The retina

Question 2

Describe rod cells (5)

Answer 2

1. The pigment inside the rod cells (rhodopsin) is broken down by light energy.
2. As more than one rod cell is connected to a singular bipolar cell, the threshold to create a generator potential is easily reached. This is why rod cells can detect light in low levels of light. (Retinal convergence causes summation).
3. When enough rhodopsin has been broken down, this creates a generator potential.
4. Rod cells can only detect black and white as they cannot distinguish different wavelengths of light.
5. Because they are connected to one bipolar cell, this creates low visual acuity, as the retinal convergence means the brain cannot distinguish between the separate sources of light.

Question 3

Describe cone cells

Answer 3

1. There are three different types of cone cells, with different types of iodopsin. They each absorb different wavelengths of light. (Red, blue and green).
2. Depending on the proportion of each type cone cell that is stimulated, we perceive colour images.
3. Iodopsin can only be broken down when there is a higher light intensity as there is only a singular bipolar cell attached to the cone cell.
4. As there is only one bipolar cell attached to each cone cell, this creates higher visual acuity.

Question 4

distribution of rod and cone cells

Answer 4

High concentration of cone cells in the fovea for high visual acuity
Rod cells are distributed around the peripheral area of the eyes