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25 Cards in this Set

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What is the strongest refractive part of the eye?
The cornea
What muscles change the shape of the lens?
Ciliary muscles

Relaxed when flat
During accommodation, are the ciliary muscles relaxed or contracted?
Contracts
In myopia (near sighted), where do the light rays converge?
INSIDE/BEFORE the retina
In hyperopia, where do the light rays converge?
BEHIND the retina
Where do the light rays converge in an astigmatism?
Point behind the retina and dispersed to create a blurred image
What are the 3 layers of the retina (from outside to inside)?
1. Ganglion cell layer

2. Inner Nuclear Layer

3. Outer Nuclear Layer
What are the only cells in the retina that actually produce AP's?
ganglion Cells
What layer contains the photoreceptors?
Outer Nuclear layer
Inner Nuclear Layer contains what type of cells?
Horizontal cells, Bipolar cells, amacrine cells
What are the 2 characteristics of the fovea that allows to increase visual acuity?
1. No blood vessels

2. Inner nuclear and ganglion cell layers removed so only photreceptors (outer nuclear layer) is present
The fovea only contains what type of photoreceptor?
Cones
What are the 3 colors of cones?
Red, Green, Blue
What is the protein that captures photons?
Rhodopsin
What is the signal cascade when a rod absorbs a photon?
1. Rhodopsin activate G protein

2. G protiein activates enzyme that degrades cGMP to GMP

3. Removal of cGMP CLOSES cCMP gates Na+ channel and HYPERPOLARIZES cell
In the dark, what is the state of photreceptors in terms of release of NT and polarization?
DEPOLARIZED are CONSTANTLY releasing glutamate
What cell synapses on photoreceptors?
2 Bi-polar cells (one off/one on) on each photoreceptor
What are the 2 types of bi-polar cells?
1. On-bipolar - glutamate is inhibitory. Become depolarized as light INCREASES

2. Off-bipolar - glutamate i excitatory. Become hyperpolarized in the light
What cells compose the 2 major LATERAL pathways in the retina?
1. Amacrine (inner plexiform layer)

2. Horizontal Cells (outer plexiform layer)
What are Horizontal cells in terms of NT and action?
GABAergic and their action is always OPPOSITE to that of the photoreceptor input
What is the relationship between photreceptor input and H-cell input?
ANTAGONISTIC
Receptive fields have what type of organization?
Center-surround
What is the function of the ganglion cells?
Merely recode the bipolar signal into spikes

Have ON-ganglion cells and OFF-gaglion cells
What are the 2 main types of ganglion cells?
1. Midget - receive from single bi-polar cells. Tiny RF's, good acuity, small dendritic tree.

2. Parasol - Receive from many bi-polar cells. Large RF, poor acuity, SENSE MOTION
M cells are what?

P cells are what?
M cells = parasol

P cells = midget