Visual System Flashcards
What structure performs the following function?
contains nuclei of ganglion cells
ganglion cell layer (GCL)
What are the three parts of the uvea?
choroid, ciliary body, iris
Does the lens have vasculature?
No, it is avascular and with little ECM
What structure performs the following function?
absorbs scattered light
retinal pigment epithelium (RPE)
Are there organelles in the body of the lens?
No, just lens fibers
What is the posterior surface of the iris lined with?
a double layer of pigmented epithelium (absorbs light)
What structure performs the following function?
contains nuclei of bipolar neurons (also nuclei of horizontal and amacrine neurons and Muller glia)
inner nuclear layer (INL)
What determines eye color?
The number of melanocytes int he anterior aspect of the iris
Retinal ganglion cell fibers synapse onto nuclei of the superior colliculus for what purpose?
for orienting the movements of head and eyes and directing the eyes to regions of interest
What structure performs the following function?
outer segment renewal
retinal pigment epithelium (RPE)
What are the three regions of the ciliary body?
vitreous body, sclera, posterior chamber/lens
What structure performs the following function?
secretion of growth factors for maintenance and structural integrity of retina
retinal pigment epithelium (RPE)
What are the three layers of the choroid?
- vessel layer
- chorocapillary layer
- Bruch’s membrane
What is it called when another disease causes or contributes to incresed eye pressure, resulting in optic nerve damage and vison loss?
secondary glaucoma
From where does the central retinal artery emerge?
from the optic nerve and before that the ophthalmic artery
True or false:
The vitreous body contains a large number of cells
False, it is nearly acellular
What is hyperopia and how is it caused?
Farsightedness
Close up objects appear blurry because they are focused on a point beyond the retina
Eye too short
What supports the lens in the eye?
A system of fibers (suspensory ligament or zonules) attached to the ciliary body
What do the outer segments of photoreceptors do?
they are flattened membrane discs with photosensitive visual pigments
Describe rods.
- long, slender outer segments
- numerous except at fovea
- very light sensitive
Which photoreceptor’s outer folds pinch off so the discs become free-floating within the outer segment?
rods
What does the anterior aspect of the iris contain?
- vascularature
- loose CT
- melanocytes
When the ciliary muscles relax, what happens to the lens?
The lens gets thinner, allowing one to focus on distant objects
Describe parasympathetic control of intraocular eye muscles
Parasympathetic stimulation causes the sphincter pupillae muscle to contract its concentric smooth muscle bundles
The pupil constricts
What structure performs the following function?
serves as the basement membrane of Muller glial cells
inner limiting lamina
When the ciliary muscles contract, what happens to the lens?
The lens thickens, allowing one to focus on near objects
What is myopia and how is it caused?
Nearsightedness
Can’t see faraway objects because they are focused in front of the retina
The eye is too long
What structure performs the following function?
contains axons and ganglion cells that converge to form the optic nerve
nerve fiber layer (NFL)
What structure performs the following function?
nutritive function
very transparent structure, 99% water & avascular
vitreous body
What is it called when optic nerve damage has occurred despite a normal intraocular pressure (IOP)?
normal tension glaucoma
What do the inner segments of photoreceptors do?
they have organelles for protein synthesis and energy production
What structure performs the following function?
3-4 micron thick amorphous hyaline membrane that the retinal pigmented epithelia rests upon
Bruch’s membrane
red/yellow melanins
pheomelanin
What structure performs the following function?
covers lens, regulates amount of light reaching the retina
iris
Which type of glaucoma accounts for 80-85% of all cases and is due to an obstruction in the drainage system of the eye?
open-angle or chronic glaucoma
black/brown melanins
eumelanin
Describe cones.
- conical outer segments with membrane discs
- responsible for high acuity and color vision
- peak density at fovea
What type of glaucoma results from poor access to the drainage system in the eye because the angle between the iris and the cornea narrows?
angle-closure glaucoma
What structure performs the following function?
is the location of synapses of rod and cone axons with next layer of neurons (bipolar)
outer plexiform layer (OPL)
When focused on distant objects, the lens is (thinner / thicker)?
thinner
What structure performs the following function?
transports nutrients and ions between photoreceptors & choriocapillaris
retinal pigment epithelium (RPE)
What structure performs the following function?
reisomerization of all-trans retinal
retinal pigment epithelium (RPE)
What structure performs the following function?
spatial buffering of ions in the subretinal space
retinal pigment epithelium (RPE)
Describe sympathetic control of intraocular muscles
Sympathetic stimulation causes the dilator pupillae to contract its radially arranged fibers
Pupil dilation
What are the two layers of the retina?
Neural or sensory retina
Retinal pigment epithelium (RPE)
Blood supply of the retina
outer - choriocapillaries
inner - central retinal artery
What structure performs the following function?
contains nuclei of rods and cones
outer nuclear layer (ONL)
Retinal ganglion cell fibers synapse onto nuclei of the pretectum for what purpose?
for pupillary reflex and control of lens
When focused on near objects, the lens is (thinner / thicker)?
thicker
What structure performs the following function?
contains synapses of bipolar axons with ganglion cells
inner plexiform layer (IPL)
What are the major macromolecules of the vitreous body?
type 2 collagen and hyaluronic acid
How much blood flow does the choroid receive and what other structure does it maintain?
The choroid receives 65-86% of the blood flow (from choriocapillaries) and is vital for the maintenance of the outer retina (particular the photoreceptors)
