Photoreceptor+cells

Photoreceptor cells are neurons modified so they are sensitive to light. {Aubusson, Eileen Kennedy Peter. //Biology in Context: the Spectrum of Life//. Victoria : Oxford Uni. Press., 2001. Print.} There are two different types of photoreceptor cells within the eye Rod cells and Cone cells. Rod cells are photoreceptor cells sensitive to light but do not distinguish between colours. Cone cells are photoreceptor cells which are not very sensitive to light but are sensitive to colour. Within both rods and cones there is a light sensitive pigment unique to either. Rods have Rhodopsins and cones have Photopsins Light is focused on the fovea, where there is a high concentration of cones. The light is absorbed by the rods and cones and after a serier of steps the electrochemical signal is sent to the brain through the optic nerve for interpretations as the sodium and potassium ions move across the cell membrane of the neurone.

Aubusson, Eileen Kennedy Peter. //Biology in Context: the Spectrum of Life//. Victoria : Oxford Uni. Press., 2001. Print. "HSC Online." //NSW HSC Online//. N.p., n.d. Web. 25 June 2010. . "Lesson Ideas: Optics: Worksheet 2." //Worksheet 2: The Human Eye - structure and function.//. N.p., n.d. Web. 25 June 2010. .