Visual System Flashcards
What are the three layers of the eyeball?
fibrous tubic, vascular tunic, and retina
What does the fibrous tunic serve as (function)?
as an attachment of extraocular muscles
What is the fibrous tunic made up of?
dense connective tissue
What structures are part of the fibrous tunic?
the sclera and cornea
Why is the cornea transparent?
because the stroma is regularly arranged
Are there nerves or blood vessels in the cornea or both?
there are only nerves in the cornea
What is keratitis?
inflammation of the cornea
What is the difference between ulcerative keratitis and keratitis?
in ulcerative keratitis the corneal stroma is also affected
What are the structures of the vascular tunic?
chorid, ciliary body, and iris
What is the function of the chorid?
it provides nutritive function to the outer retina
What is the chorid made out of?
loose connective tissue
The choroid is pigmented, what does that allow it to do?
absorb stray photons of light
What part of the choroid is not pigmented?
the tapetum lucidim
What is the function of the tapetum lucidum?
it reflects light enhancing low light vision
Where is the tapetum lucidim located?
in the dorsal portion of the choroid
What is the choriocapillary layer and where is it located?
it is a bed of capillaries adjacent to the retina
What does the ciliary epithelium do?
secretes aqueous humor
What do the ciliary processes of the ciliary body do?
they hold the lens in place
What are the ciliary processes attached to the lens with?
zonular fibers
What is the ciliary muscle innervated by?
the ciliary ganglion
What is the function of the ciliary muscle?
it focuses light by changing thickness of the lens
What does the contraction of the ciliary muscle do?
it releases pressure on the lense
What does relaxation of the ciliary muscle do?
it stretches the lens
Where is the iris located?
rostral to the lens
What does the iris form?
the pupil
What does the iris deterine?
eye color
What muscles are located in the iris?
pupillary constrictors and dilators
What type of innervation controls pupillary constriction?
parasympathetic innervation from the occulomotor
What type of innervation controls pupillary dilation?
sympathetic innervation from the trigeminal nerve
What type of arrangement is the pupillary constrictor?
it is circularly arranged
What type of arrangement is the pupillary dilator?
it is radially arranged
Where is the retina located?
it is the innermost tunic of the globe
What are the layers of the retina?
rods and cones, outer nuclear, inner nuclear, and ganglion
What does the outer nuclear layer contain?
photoreceptors
What does the inner nuclear layer contain?
inner retinal neurons
What does the ganglino layer contain?
retinal ganglion cells
Where is the blind spot of the eye?
where the optic nerve head is
What is located in the optic nerve head?
the optic disk
What provides blood supply to the inner retina?
vessels that enter and exit through the optic nerve head
What provides blood supply to the outer retina?
the choroid
What are the chambers of the eye?
anterior chamber, posterior chamber, and posterior segment
Which chamber is filled with aqueous humor?
the anterior and posterior chamber
What chamber is filled with vitreous humor?
the posterior segment
What provides intraocular pressure?
intraocular fluid
What causes glaucoma?
increased intraocular pressure which leads to death of retinal ganglion cells
What are the outersegments like for rods?
long
What are the outersegments like for cones?
short and cone-like
Why do rods and cones have different pigments?
because they absorb light at different wavelengths
Do cones work better in the light or dark and why?
in the light because in the dark there is not enough light to activate them
Do rods work in light?
nope
What does high acuity vision require?
a high concentration of cones
What is the fovea or area centralis?
where cones bunch together closely
Are there more rods or cones in the eye?
rods
What is phototransduction?
the process of a photon of light being transduced into something the brain can understand
Where can the nucelus of a cell body of the rod/cone be found in?
the outer nuclear layer
What is rhodopsin?
opsin plus chromaphore
What is rhodopsin involved in?
phototransduction
How does rhodopsin work in phototransduction?
the chromophore in rhodopsin absorbs light and then isomerizes
What can cause retinal degeneration?
retinal detachment, vitamin A deficiency, inhereted recessive genes, tauring deficiency, and mutations in the retinal pigment epithelium (RPE 65)
How do you evaluate retinal function?
electroretinography, fundus images, or optical coherence tomography
What is the track of visual projection?
lights leave the retina via the optic nerve, go to the optic chiasm, and then go to the optic tract
What are the major visual targets?
lateral geniculate nucleus of the thalamus, pretectal nucleus, and rostral colliculus
What is the lateral geniculate nucleus of the thalamus in charge of?
conscious perception
What does the lateral geniculate nucleus relay information to?
the cortex
What does the pretectal nucleus project to?
the parasympathetic nucleus of III
What reflex is the pretectal nucleus in charge of?
the pupillary light reflex
Where is the rostral colliculus located?
caudal to the pretectal nucleus in the tectum of the midbrain
What does the rostral colliculus mediate?
visual reflexes from both eyes
What descending tracts are associated with the rostral colliculus?
the contralateral tectospinal and tectotegmentospinal tract
What reflex is the rostral colliculus associated with?
the body ocular reflex
What is the body ocular reflex?
when the eyes and upper body orient towards the object that suddenly enters the visual field
What does the rostral colliculus project to?
the motor nuclei of III, IV, VI, the tectospinal tract, the motor nucleus of XI, and spinal nerves from the cervical cord
What is the direct response of the pupillary light reflex?
when the pupil contracts in the eye that the light is shown in
What is the consensual response of the pupillary light reflex?
when the pupil contracts in the eye that light is not shown in
What structures are involved in pupillary dilation?
rostral colliculus and descending tract of the lateral funiculus
