vision Flashcards
Uveal tract- 3 parts
Choroid, Ciliary body, Iris
Choroid
lots of capillaries that supply
the photoreceptor cells; contains melanin (absorbs light)
Ciliary body
: encircles the lens. Muscular component refractive power of lens Vascular component
Sclera
tough, white fibrous tissue
surrounding most of the eye
Vitreous humor:
thick, gelatinous substance that fills the space
between the lens and the retina
Anterior chamber of the eye
between cornea and lens(contains aqueus humor)
Posterior chamber
between the lens and the iris(Aqueous humor is produced here and flows out through the pupil
Aqueous Humor gets replaced X times a day
12
Glaucoma
increased intraocular pressure reduce blood supply to the
eye damage to retinal neurons
Cataracts
Opacities in the lens
Accommodation
dynamic changes in the shape of the lens
Ametropia
having some sort of refractive error
Near-sighted (myopia)
unable to bring distant objects into focus
Far-sighted (hyperopic)
unable to bring close objects into focus
Fundus
surface of the retina
Optic disk (optic papilla)
blood supply enters and exits from here; also where
retinal axons exit
Macula lutea
circular; near center of the
retina, Supports high visual acuity
Photoreceptors
rods and cones,Outer segment contains membranous
disks that contain light-sensitive
pigments
pigment epithelium
Eat (phagocytose) old membranous disks filled
with pigment (lifespan of disk= 12 days) Regenerate photopigment molecules after
exposure to light
Rods
mediate vision in low light
conditions (scotopic vision
Cones
mediate vision in normal or higher
lighting conditions (photopic vision);
responsible for color vision; high spatial
acuity
mesopic vision
during mid-
light (dusk/dawn) conditions
photopic vision
normal or higher
lighting conditions
scotopic vision
low light
conditions
How do we “return things to normal” after light hits a photoreceptor
arrestin;Converted to all-trans retinol
Who sends axons from the retina to the brain?
ganglion cells
optic nerve
retinal ganglion cells exit
through the optic disk and bundle
together
optic chiasm
The optic nerves from each side of the
head meet; some cross over
optic tract
after chiasm contains info from both eyes
Targets of Optic Tract
Dorsolateral geniculate nucleus, Pretectum,Suprachiasmatic nucleus, Superior colliculus
Dorsolateral geniculate nucleus(Lateral Geniculate Nucleus)
Send their axons through part of the
internal capsule (optic radiation) to
the primary visual cortex
Pretectum
Coordination center for the pupillary light reflex
Receives bilateral input (info from both eyes)
Pupillary Light Reflex
Use to test the function of the eye, the motor outflow to the pupil, and the
paths in between
* Normal: both pupils will respond the same even if you shine the light in
one eye
Suprachiasmatic nucleus
Receives equal input from right and left eyes via the
retinohypothalamic pathway
photoentrainment and circadian rhythms
Superior Colliculus
Coordinates head and eye movements
to visual targets
Anopsias(Optic nerve damage)
no
vision from that eye
Anopsias(Optic chiasm damage)
involves both eyes
(peripheral usually
Anopsias(Optic tract damage)
both
eyes, but generally from the
same side of field
Anopsias(Optic radiation damage)
more specified field of view
missing, but can depend on
where it is
M ganglion cells
larger receptive fields,
larger cell bodies, and larger diameter axons
(faster) than P ganglion cells
P ganglion cells
can transmit color
information and M ganglion cells cannot, but
both receive input from cones
Koniocellular
important for
some aspects of color vision and project
to Layers 2/3 instead of 4
Dorsal stream
Information from the primary visual cortex to the posterior parietal cortex. It’s responsible for localizing objects in space and guiding actions.
ventral stream
Visual information from the primary visual cortex to the temporal lobe.carries information related to object form and recognition.
