Visual System Flashcards by sophia cordova

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layers of the eye

fibrous
vascular
inner (neural/retinal)

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fibrous layer contains the…

cornea
sclera

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The transparent, curved structure at the
front of the eye that helps to focus light onto the retina.

cornea

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The tough, white outer covering of the eye
that provides structural support and protection

sclera

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contact lens sits on the top of…

cornea

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what provides about 65-75% of eyes focusing power?

cornea

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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

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symptoms of cornea damage

pain, redness, blurred vision, tearing, and
light sensitivity

severe: scarring, vision impairment, infection, or
permanent vision loss if untreated

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vascular layer of the eye contains (3)

choroid
ciliary body
iris

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The layer rich in blood vessels that nourishes the retina and absorbs stray light.

choroid

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Contains muscles that control the shape of the lens for focusing and produces aqueous humor, the fluid in the eye.

ciliary body

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The colored part of the eye that controls the diameter of the pupil, regulating the amount of light that enters the eye.

iris

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what is the largest part of the vascular layer?

choroid

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choroid is firmly attached to the

retina

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choroid is fed by

ciliary branches of ophthalmic artery

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choroid helps supply blood to the

photoreceptors

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choroidal neovascularization

a condition where abnormal blood vessels grow in the choroid layer of the eye

can lead to vision distortion and loss

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ciliary muscle contract…

contract –> lens round –> more refraction –> clear CLOSE vision

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ciliary muscles relax…

relax –> lens flattens –> less refraction –> clear DISTANCE vision

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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.

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circular and radial muscles of the eye

radial: dilator papillae
circular: sphincter pupillae

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contraction of the dilator pupillae m.

pupil opens wide (dim light)

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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?

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

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

1. Light hits retina, photoreceptors activated 2. Sensory input from optic nerve 3. Signal processing in pretectal nucleus (CNS level: midbrain) 4. Bilateral response with signals sent to both right and left Edinger-Westphal nuclei 5. Parasympathetic activation: neurons from Edinger-Westphal nucleus send signals along CN III to ciliary ganglion 6. Activation of sphincter pupillae muscle, causing it to contract 7. 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)