Unit 2: Visual System Flashcards
What is the structure that makes up the visual center?
Macula lutea
What receptors is the macula lutea comprised of?
Cones because it’s the area of high visual acuity
What is the structures that is a depression in the center of the macula lutea?
Fovea centralis
The fovea centralis is made of what?
Foveola (cones only)
Because this is where visual acuity of foveola that is the highest
What is the peripheral border of the functional retina called?
Ora serrata
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
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.
What is the name of the neurons of the retina?
Bipolar cells
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
Neurons that innervate bipolar cells are called:
Ganglion cells
What part of the retina is best suited for low resolution vision, low light vision?
Peripheral retina
Because it mostly contains rods
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.
What do axons of ganglion cells of the retina form?
Optic nerves
Fibers from nasal halves of each retina decussate here (temporal fibers, which do not decussate)
Optic chiasm
Fibers within this structure carry visual data from contralateral visual field:
Optic tracts
The right optic tract carries visual data from the ___ visual field
Left
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
Optic tracts project into the:
Lateral geniculate body/nucleus (LGB/LGB) of the thalamus
What nucleus relays neurons for visual data?
LGB/LGN (thalamus)
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
Meyer’s loop relays visual information from the ________ of the visual field
Contralateral upper quandrant
What initiates the processing of visual data?
Primary visual cortex (V1)
where is the primary visual cortex (V1) located?
Upper and lower banks of calcarine sulcus (occipital lobe)
Corresponds with Brodmann map area 17
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
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?
- Start from optic tract.
- Travels through superior brachium.
- Synapses on superior colliculus.
- 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
