Visual System Flashcards
layers of the eye
fibrous
vascular
inner (neural/retinal)
fibrous layer contains the…
cornea
sclera
The transparent, curved structure at the
front of the eye that helps to focus light onto the retina.
cornea
The tough, white outer covering of the eye
that provides structural support and protection
sclera
contact lens sits on the top of…
cornea
what provides about 65-75% of eyes focusing power?
cornea
how does the cornea become damaged? (5)
Physical trauma (like scratches or foreign
objects)
infections
excessive exposure to UV light
chemical exposure
long-term dryness of the eyes
symptoms of cornea damage
pain, redness, blurred vision, tearing, and
light sensitivity
severe: scarring, vision impairment, infection, or
permanent vision loss if untreated
vascular layer of the eye contains (3)
choroid
ciliary body
iris
The layer rich in blood vessels that nourishes the retina and absorbs stray light.
choroid
Contains muscles that control the shape of the lens for focusing and produces aqueous humor, the fluid in the eye.
ciliary body
The colored part of the eye that controls the diameter of the pupil, regulating the amount of light that enters the eye.
iris
what is the largest part of the vascular layer?
choroid
choroid is firmly attached to the
retina
choroid is fed by
ciliary branches of ophthalmic artery
choroid helps supply blood to the
photoreceptors
choroidal neovascularization
a condition where abnormal blood vessels grow in the choroid layer of the eye
can lead to vision distortion and loss
ciliary muscle contract…
contract –> lens round –> more refraction –> clear CLOSE vision
ciliary muscles relax…
relax –> lens flattens –> less refraction –> clear DISTANCE vision
The eye flips the image due to the refraction of light through the
cornea and lens, projecting an inverted image onto the ____,
which the brain then processes and interprets as upright
The eye flips the image due to the refraction of light through the cornea and lens, projecting an inverted image onto the retina, which the brain then processes and interprets as upright.
circular and radial muscles of the eye
radial: dilator papillae
circular: sphincter pupillae
contraction of the dilator pupillae m.
pupil opens wide (dim light)
contraction of the sphincter pupillae m.
pupil reduces in size (bright light)
what does the eye contract in dim and bright light?
dim: dilator pupillae (dilate)
bright: sphincter pupillae (shrink)
inner layer of eye contains… (3)
retina
optic disc
fovea
The central area of the retina with a high concentration of cones, providing sharp central vision, with the fovea being the
point of highest visual acuity
fovea
The spot where the optic nerve exits the eye, often referred to as the “blind spot” due to the absence of photoreceptors
optic disc
Contains photoreceptor cells (rods and cones) that convert light into neural signals for vision.
retina
specialized cells in the retina that convert light into electrical signals
Phototransducers (rods and cones)
rods: function, characteristics, distribution
Function: Responsible for vision in low light (scotopic vision).
Characteristics: High sensitivity to light but do not detect color.
Distribution: Concentrated in the peripheral regions of the retina.
cones: function, characteristics, distribution
Function: Enable color vision and detailed visual acuity (photopic vision).
Characteristics: Three types (S, M, and L cones) sensitive to short (blue), medium (green), and long (red) wavelengths.
Distribution: Densely packed in the fovea, where high-resolution vision occurs
The axons of the ganglion cells are
found in the ____ ____ layer and all
run toward the optic disc where they
become the __ ___.
nerve fiber
optic nerve
does the optic disc have photoreceptors?
no
fovea is the “ “
central vision
fovea has the highest
aquity
the fovea contains only
cones
(no rods)
The fovea covers only about __% of the retina but accounts for over __% of the visual cortex’s processing.
1%
50%
the LGN receives projections from __% of
retinal ganglion cell axons
90
the LGN is composed of __ layers, each
maintaining a ____ ____
six
retinotopic map
*layers receive input from one eye
the optic radiations are responsible for…
carrying the entire visual field information to the visual cortex
Meyer’s loop is a subset of the
optic radiations
*fibers that project through the temporal lobe
Meyer’s Loop curves around the ___ ___ of the lateral ventricle before projecting to the visual cortex in the occipital lobe
temporal horn
V1 or Brodmann area 17 AKA
primary visual cortex
the primary visual cortex is located
in the occipital lobe at the back
of the brain
calcarine sulcus
Separates the superior and inferior portions of the primary visual cortex
vision goes above/below the calcarine sulcus
upper vision: below sulcus
lower vision: above sulcus
why test pupillary reflex?
If you shine a light in one eye, both pupils should constrict at the same time.
*consensual response
pupillary reflex in words
- Light hits retina, photoreceptors activated
- Sensory input from optic nerve
- Signal processing in pretectal nucleus (CNS level: midbrain)
- Bilateral response with signals sent to both right and left Edinger-Westphal nuclei
- Parasympathetic activation: neurons from Edinger-Westphal nucleus send signals along CN III to ciliary ganglion
- Activation of sphincter pupillae muscle, causing it to contract
- Pupil constriction
pupillary reflex neural pathway
pupillary dilation sympathetic pathway (1st, 2nd, 3rd order neurons)
First-Order Neurons: The process begins
in the hypothalamus, where the first-order
neurons originate. These neurons travel
down through the brainstem and synapse
in the spinal cord at levels C8-T2.
Second-Order Neurons: Exit the spinal
cord and ascend through the sympathetic
chain to the superior cervical ganglion,
located near the carotid artery.
Third-Order Neurons: After synapsing in the superior
cervical ganglion, third-order neurons travel alongside
the internal carotid artery, following its pathway into the
skull. They then continue to the eye, following branches
of the ophthalmic division of the trigeminal nerve
pupillary dilation sympathetic pathway diagram
horner syndrome
Loss of sympathetic
innervation, characterized by 3 main features:
1. Miosis — constricted pupil (loss of dilator)
2. Ptosis — drooping of upper eye lid (loss of superior tarsal muscle)
3. Anhydrous — loss of sweating
eye muscles sympathetic vs parasympathetic response
symp: dilator pupillae (dilates pupil)
parasymp: sphincter pupillae (narrows pupil)
A. right CN II (optic nerve)
D. left CN III (oculomotor nerve)
