Chapter 10.3, Problem 10.5.2QC

Summary Introduction

To write:

About the cGMP levels greatest in photoreceptors- when they are exposed to light or when they are exposed to dark and the effects cGMP has on sodium channels in the external/outer segment of the photoreceptors.

Introduction:

Retina- situated the backside of the eye is made up of photoreceptive cells known as the Rods and Cones. It is responsible for the transduction of light into nervous impulses. Rods contain a chromophore 11-cis retinal which is attached to the cell membrane protein, opsin.

G-proteins act as mediators of cell signaling pathways and require signaling molecules which are called the second messengers. Cyclic-GMP is a G-protein signaling cascade in photo transduction.

There is a biological change of a photon into an electrical signal in the retina. This process is carried out by the G-protein coupled receptors called opsins. The photons are absorbed by the rhodopsin and converted into electrical current.