8.4 Vision Flashcards
What produces the aqueous humor?
cilliary processes
Functions of aqueous humor?
- provides nutrients for the lens and cornea
- creates refractive power of the eye
Vascular part of the eye includes
Choroid
ciliary body
iris
What gives the majority of refractive power of the eye
What controlls the ciliary muscles?
Parasympathetic NS
Describe the müller cells
Long glial cells
maintain extracellular environment by regulating K+ levels
NT uptake
glycogen storage
Who is more sensitive to light and why
Rods
bcs. In cones only a few synaps on a bipolar cell
Difference in activation of rods and cones?
rods have more Rhodopsin so less photons are needed for the activation of it (only one photn is needed)
What does Rhodopsin contain
Opsin and Retinal
Draw a diagram of photoreception
Define what is near point
the point nearest the eye at which an object is accurately focused on the retina when the maximum degree of accommodation is employed
How does the eyeball look like im hyperopia?
short eyeball
corrected by convex lens
How does the eyeball look like im myopia?
Long eye
fixed with concave lenses
What is the pressure inside the eyeball?
22 mmHg (Bernandlevi)
Describe the flow of the aqueous humor
What is the major refractive element of the eye?
Cornea (43 diopter)
What holds the lens in place?
Describe the layers of the retina
The eye can dist. 2 aspects of light
______
______
What are cones responsible for?
Best in day light, color vision
Main visual pathway in thalamus is ______
LGB
Lens equation
Focal power of resting and accommodation (what cahnges?)
What is astigmatisms?
Unequal focal power on different directions
What is the intraocular pressure?
15mmHg
What happens in glaucoma?
Intraocular pressur increases -> optic nerve damage -> vision loss
Distribution of rods and cons in the retina
Three types pf vision
Scotopic (only rods)
mesopic (both)
photopic (only cones)
What is Rhodopsin?
Visual pigment
GPCR for light
Rhodopsib = opsin (7TM protein) + 11-cis retinal
What happens in vit A deff?
Night blindness
Phototransduction of rods in light
Light ► Rhodopsin (changes to metarhodopsin II) ►
Gt activation (transducin) ► at acrivstes cGMP Phosphodiesterase (PDE) ► cGMP decreases ►
CNG (Cyclic Nucleotide Gated) channels close (Na, Ca influx decreases) ► hyperpolarization ► Glu release decreases
Describe the dark current of photoreceptors
CGMP is always produced and not broken down so CNG channels are open and influx of Na and Ca happens ► depol ► Glu release
What does light evokes in photoreceptors?
Define Critical Flicker Fusion Frequency
the frequency at which a flickering light is perceived as continuous
When does Rhodopsin form?
Two things can happen when hypopolarization of the photoreceptor membrane
There are two types of receptors on _____ and _____cells
- _____
- _____
There are two types of receptors on bipolar and horizontal cells
- Ionotropic
- Metabotropic
ionotropic receptors, which are depolarizing (excitatory), and metabo- tropic receptors, which are hyperpolarizing (inhibitory)
ionotropic receptors, which are depolarizing (excitatory), and metabo- tropic receptors, which are hyperpolarizing (inhibitory)
Draw the optic pathway
Why are horizontal cells important?
Explain of herman grid illusion
3 types of cones:
1) blue S (short)
2) green M (medium)
3) red L (large)
by wavelength
3 layers of the eye
- outer fibrous (sclera, cornea)
2.
