Unit 2: Visual System Flashcards by Beck Forsland

What is the structure that makes up the visual center?

Macula lutea

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What receptors is the macula lutea comprised of?

Cones because it’s the area of high visual acuity

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What is the structures that is a depression in the center of the macula lutea?

Fovea centralis

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The fovea centralis is made of what?

Foveola (cones only)

Because this is where visual acuity of foveola that is the highest

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What is the peripheral border of the functional retina called?

Ora serrata

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There is an area of convergence of fibers of ganglion cells that form the optic nerve. What is this area called?

Optic papilla or the optic disc

This is medial (nasal) and superior to the macula

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What is the retinal “blind spot” that has no rods or cones?

The optic papilla or optic disc.

This is where the fibers of ganglion cells converge to form the optic nerve. That’s why there are no rods or cones.

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What is the name of the neurons of the retina?

Bipolar cells

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The convergence of many rods to one bipolar cell results in:

Summation

The rod system provides for vision of low resolution/acuity and also provides for vision in low light conditions.

10 rods/bipolar cell near macula lutea
100 rods/bipolar cell near ora serrata

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Neurons that innervate bipolar cells are called:

Ganglion cells

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What part of the retina is best suited for low resolution vision, low light vision?

Peripheral retina

Because it mostly contains rods

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What part of the retina is best suited for color vision, high resolution vision?

Macular retina

Because it is comprised mostly of cones and very little or no convergence of bipolar cells on rods.

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What do axons of ganglion cells of the retina form?

Optic nerves

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Fibers from nasal halves of each retina decussate here (temporal fibers, which do not decussate)

Optic chiasm

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Fibers within this structure carry visual data from contralateral visual field:

Optic tracts

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The right optic tract carries visual data from the ___ visual field

Left

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Fibers within the right optic tract are from ganglion cells located in the:

Right (nasal) half of the left retina

Right (temporal) half of the right retina

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Optic tracts project into the:

Lateral geniculate body/nucleus (LGB/LGB) of the thalamus

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What nucleus relays neurons for visual data?

LGB/LGN (thalamus)

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What is the pathway of vision to the cortex from the optic tracts?

LGB neurons send axons to posterior limb of internal capsule and then to the cerebral cortex on the medial aspect of the occipital lobe

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Meyer’s loop relays visual information from the ________ of the visual field

Contralateral upper quandrant

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What initiates the processing of visual data?

Primary visual cortex (V1)

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where is the primary visual cortex (V1) located?

Upper and lower banks of calcarine sulcus (occipital lobe)

Corresponds with Brodmann map area 17

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Primary Visual Cortex maintains retinotopic organization. Where is the macular visual field located in the Primary Visual Cortex (v1)?

Posterior 1/3 of visual cortex

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Primary Visual Cortex maintains retinotopic organization. Where is the peripheral visual field located in the Primary Visual Cortex (v1)?

Anterior 2/3 of visual cortex

Primary Visual Cortex maintains retinotopic organization. Where is the contralateral lower quadrant of the Primary Visual Cortex (v1)?

Upper banks fo calcarine sulcus

Primary Visual Cortex maintains retinotopic organization. Where is the contralateral upper quadrant in the Primary Visual Cortex (v1)?

Lower banks of calcarine sulcus

What is the thing that functions to allow for conscious awareness of visual stimuli?

Primary Visual Cortex (v1)

What would a lesion of the cortex adjacent to calcarine sulcus (v1)?

Cortical blindness

What would a unilateral lesion to the Calcarine Sulcus (v1) do? (One side of cortex is damaged)

Loss of vision in the contralateral half of the visual field in both eyes

Where is the visual association cortex located?

Medial/lateral portion of occipital lobe (Also the inferolateral temporal and som areas of posterior parietal) Corresponds with Brodmann map areas 18, 19

Which gyri process the visual association cortex?

Cuneate Gyrus and Lingual Gyrus

What receives input from 1˚ visual cortex & other brain regions and integrates current visual data with previous experiences with visual data? Ie recognize objects, faces, shapes, colors and appreciate motions, relations, and computations mediated in movement

Visual Association Cortex

If the primary visual association cortex is intact, a lesion of the visual association cortex may result in:

Visual agnosia or facial agnosia | No blindness

Visual agnosia

Inability to appreciate significant of visual information

Facial agnosia

Inability to identify familiar faces May have difficulty distinguishing biological sex, age, emotional state

What coordinates activities controlled by the hypothalamus that are dependent on circadian rhythms?

Suprachiasmatic nucleus

Where is the retinohypothalamic tract going?

Ganglia from retina go to suprachiasmatic nucleus in the hypothalamus

What fibers influence pupillary light reflex/respons?

Retinotectal fibers

What influences avoidance reflex (involuntary/reflexive movement in response to object in visual field traveling at high velocity)?

Retinotectal fibers

Where are retinotectal fibers going?

1. Start from optic tract. 2. Travels through superior brachium. 3. Synapses on superior colliculus. 4. To the tectum

What fibers coordinate visually-dependent involuntary reflexes of the eyes such as tracking a moving object across the visual field?

Corticotectal fibers

Tell me the tract of cortico-tectal fibers

``` Start at the occipital cortex Travels in the geniculocalcarine tract Traverses the superior brachium (Does NOT go through thalamus) Synapses in superior colliculus (tectum) ```

Anopsia (anoxia)

Loss of vision

Hemianopsia (hemianopia)

Loss of vision in the 1/2 of the visual field

Quadrantanopsia (quadrantanopia)

Loss of vision in 1/4 of the visual field

Homonymous

Same

Example: right homonymous hemianopsia

Same deficit in both eyes and the deficit is in the right half of visual field

Lesion of R optic nerve Which eye (R/L/Both) and what part of visual field is affected?

Right Eye Visualization on page 29

Lesion of R optic nerve What is our deficit?

Entire visual field for right eye = right eye blindness = right eye anopia Pg 29

Lesion of the optic chiasm at midline Which eye (R/L/Both) and what part of visual field is affected?

Left half of visual field for left eye Right half of visual field for right eye Pg 30

Lesion of optic chiasm at midline (pituitary tumor) What is our deficit?

Bilateral hemianopsia Pg 30

Lesion: compression of right lateral margin of optic chiasm (aneurysm of internal carotid artery) Which eye (R/L/Both) and what part of visual field is affected?

Right eye, left/nasal/medial visual field Pg 32

Lesion: compression of right lateral margin of optic chiasm What is the deficit?

Nasal hemianopsia of the right eye Pg 32

Lesion of the right optic tract OR right optic radiations OR right 1˚ visual cortex Which eye (R/L/Both) and what part of visual field is affected?

Both eyes and left visual field Pg 33

Lesion of the right optic tract OR right optic radiations OR right 1˚ visual cortex What is the deficit?

Left homononymous hemianopsia Pg 33

Lesion of right Meyer’s loop (possible temporal lobe tumor) Which eye (R/L/Both) and what part of visual field is affected?

Both eyes. Left half of the visual field, and the superior quarter of that field. Pg 33

Lesion of right Meyer’s loop (possible temporal lobe tumor) What is the deficit?

Left superior homonymous quadrantanopia Pg 33

ratio of ganglion cells | to bipolar cells in fovea

1:1

Ratio of cones to bipolar cells in the fovea

1:1

rods to bipolar cell ratio | near the macula lutea

10:1

rods to bipolar cell ratio | near the ora serrata

100:1

Lesion of the visual association cortex could result in:

Facial agnosia

Where are fibers from the retinotectal fibers going?

From the retina to the tectum via superior brachial (“arm” of superior colliculus)

The image of an object projected onto the retina will be___________ and _____________.

Inverted and reversed

area seen by both eyes = ___________

Total visual field

an image from the upper left quadrant of the visual field will project onto what part of the retina in each eye?

left retina - the lower right (nasal) quadrant | Right retina - the lower right (temporal) quadrant

How is visual data organized throughout the central pathway?

Retinotopic Example: visual data from the right halves of both retina (left visual field data) will project to the right side of the brain

LGB axons form optic radiations that called ________.

geniculocalcarine tract

The geniculocalcarine tract passes around the_________ and _________ of the lateral ventricle.

collateral trigone, inferior horn

fibers of the geniculocalcarine tract that loop around the inferior horn of the lateral ventricle (temporal lobe) and synapse on lower banks of calcarine sulcus comprises ___________.

Meyer’s loop

Most of the functional area of the primary visual cortex is located where within the calcarine sulcus?

deep within sulcus, minimal amount on medial surface

Where is the photosensitive chemical rhodopsin found and how does it work?

It is found in the rod cells of the neural layer of the retina. Light changes the configuration of rhodopsin which results in a change in the membrane potential of the rod cell to allow for transduction of light information into visual data

There are three types of cone receptors which include one of three photosensitive pigments that absorb either ______, ______ or _______ light.

Red, green, blue