Answered: What occurs during phototransduction of…

Principles Of Radiographic Imaging: An Art And A Science

6th Edition

ISBN:9781337711067

Author:Richard R. Carlton, Arlene M. Adler, Vesna Balac

Publisher:Richard R. Carlton, Arlene M. Adler, Vesna Balac

Chapter33: Fluoroscopy

Section: Chapter Questions

Problem 5RQ

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Question

What occurs during phototransduction of light?

Expert Solution

Introduction

The process by which light's primary particles called the photons are converted into the electrical signals is known as phototransduction. The photoreceptor cells lying in the eye's retinal called the rods and cones are the cells through which visual phototransduction occurs.

Explanation

Steps for phototransduction:

When light enters the eye, it activates the opsin molecule as on photon absorption the cis retinal forms are converted to all-trans forms by isomerization. This causes rhodopsin activation.
Rhodopsin in activated form causes a decrease in the intracellular cyclic GMP (cGMP) concentration via transducin and cGMP phosphodiesterase activity.
The cGMP gated ion channels will close in response to low cGMP levels, and the photoreceptors' membrane, which was depolarised in the dark will become hyperpolarized.
Hyperpolarization of the membrane results in a decrease in the neurotransmitter amount, which was released onto the downstream neurons by the photoreceptors. Thus, the light stimulus is encoded by the photoreceptor cells in the chemical stimulus.