Packet 20 Chapter 49 Structure of the Eye The Retina Contains two types of photoreceptors Rods Black and white vision Cones Color vision These photoreceptors connect to a series of neurons that ultimately lead to the optic nerve which ultimately leads to the brain ID: 733566
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Slide1
The Eye & The Action (Receptor) Potential
Packet #20
Chapter #49Slide2
Structure of the EyeSlide3
The Retina
Contains two types of photoreceptors
Rods
Black and white vision
Cones
Color visionThese photoreceptors connect to a series of neurons that ultimately lead to the optic nerve which ultimately leads to the brain.Slide4
The Structure of the Rod
Contains disks that has the protein called
rhodopsin
within the disk’s membrane.
Rhodopsin
Contains two polypeptide chains called retinal and opsin
.Slide5
Retinal
Exists in two forms
Cis
isomer
Exists when there is absence of light
Trans isomerExists when there is a presence of lightSlide6
The Production of a Receptor Potential in a Rod Cell
Light isomerizes retinal, which activates
rhodopsin
.
What
type of enzyme would be used to make the change?Retinal changes from the
cis
form to the
trans
form.
Ultimately causes
rhodopsin
to
become active.Slide7
Production of a Receptor Potential I
Light isomerizes retinal, which activate
rhodopsin
.Slide8
Production of a Receptor Potential II
Active
rhodopsin
in turn activate a G protein called
transducin
.Slide9
Production of a Receptor Potential III
Transducin
activates the enzyme
phodiesterase
(PDE).Slide10
Production of a Receptor Potential IV
Activated PDE detaches cyclic
guanosine
monophosphate
(cGMP) from Na+ channels in the plasma membrane by hydrolyzing
cGMP
to GMP.Slide11
Production of a Receptor Potential IV
The sodium channels close when
cGMP
detaches. The membrane’s permeability to Na
+
decreases, and the rod hyperpolarizes.Slide12
The Big PictureSlide13
Production of a Receptor Potential VI
The action potential moves along a series of nerve cells.
Horizontal
Bipolar
Amacrine
Ganglion cellThe message ultimately reaches the optic nerve fibers which lead to the brain.Slide14
Homework
Know how the eye focuses.
Know the cause of near and far sightedness.