Vision I (part 2)

What is the process where photoreceptors convert electromagnetic radiation into neural signals?

How are the photopigments in disks membranes called?

How are the photopigments in disks membranes called?

• cCAMP

• Opsin

• Rhodopsin

• Transducin

• Retinal

What does opsin contain?

• cCAMP

• Opsin

• Rhodopsin

• Transducin

• Retinal

What is the name of the prebound agonist located in the opsin?

• cCAMP

• Opsin

• Rhodopsin

• Transducin

• Retinal

Retinal is a _______ _______ contained in the opsin.

• Prebound, agonist

• Prebound, antagonist

• Freebound, agonist

• Freebound, antagonist

Light absorption by the photoreceptors causes a change in the ________ conformation. Which causes the the ______ to bleach.

What are the steps of phototransduction?

Answer explanation

1. Light is absorbed by photoreceptor

2. Light causes change in the conformation of retinal (prebound antagonist) located in the rhodopsin

3. This causes te opsin to activate (bleaches it) which activates th transducins (G-protein)

4) Transducins activate the PDE (phosphodiesterase)

5) This reduces the level of cGMP which causes Na+ channels to close

6) Closer of NA+ causes hyperpolarization which decrease the release of glutamate

Under which conditions are photoreceptors depolarize?

• Dark

• Light

• Extreme light

• Slight changes in light

What is called the dark current?