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Ocular Block 8 > Visual Pathways > Flashcards

Visual Pathways Flashcards

1
Q

These convert light energy into a neuronal signal via the release of NT in a processes known as phototransduction

A

Photoreceptors

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2
Q

Specialized for vision in dim light (motion detection) and dominate the midperipheral and peripheral retina

A

Rods

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3
Q

Responsible fo day time vision and diffrentailly sensitive to particular wavelengths of light

A

Cones

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4
Q

Where are cones most populated

A

Macula

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5
Q

Where are there only cones

A

Very center of macula

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6
Q

Where are there no rods

A

Very center of macula

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7
Q

The signal from the photoreceptors are passes on to the ____________ and modified

A

Retinal internuerons (bipolar cells, Amacrine cells, and horizontal cells)

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8
Q

Located between the receptor cell layer and the bipolar cell layer. Their processes lie parallel to the plane of the retina. Lateral processing of information between cells

A

Horizontal cells

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9
Q

Receive inputs from photoreceptor cell and project to ganglion cells

A

Bipolar cells

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10
Q

Located between the bipolar cell layer and the ganglion cell layer. These cells modulate activity between the two layers

A

Amacrine cells

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11
Q

Internuerons relay the signal to the _______, the output cells of the retina

A

Retinal ganglion cells

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12
Q

Encoding aspects of visual information such as color, image velocity, movement direction, and contrast

A

Subsets of retinal ganglion cells will selectively encode aspects of visual information such as color, image velocity, movement direction, acuity, and contrast. The ganglion cells are encoding these aspects of vision simultaneously, but through separate channels.

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13
Q

The retinal ganglion cells send their output via axons that collectively will form the ________ to communicate with the brain

A

Optic nerve

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14
Q

Axons of the nerve fiber layer at the optic disc

A

The axons of the nerve fiber layer make a 90 degree turn in the retina at the optic disc and will exit the eye as the optic nerve.

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15
Q

When do the axons of the nerve fiber layer get myelinated

A

After they exit the eye.

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16
Q

Where do 90% of the axonal fibers synapse from the optic nerve

A

In the LGN

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17
Q

Where do 10% of the axonal fibers from the optic nerve go

A

Project to areas involved with pupil responses and circadian rhythm

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18
Q

What kind of VF loss results from a complete transaction of the optic nerve

A

Complete loss of vision in that eye

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19
Q

The optic nerves continue posteriorly giving rise to a rectangular structure, the __________

A

Optic chiasm

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20
Q

What happens on the optic chiasm

A

Visual information from the right and the left eye will cross to the contralateral side of the visual system

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21
Q

How does the visual pathway continue after the optic chiasm

A

Optic tract

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22
Q

What fibers cross to the contralateral side at the optic chiasm

A

The nasal retinal fibers. The temporal fibers remain in ipsilateral tract and do not cross over

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23
Q

What lies above the optic chiasm

A

3rd ventricle

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24
Q

What lies below the optic chiasm

A

Pituitary gland

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25
Q

What is the significance of a pituitary adenoma to the visual system

A

The gland will enlarge and compress the optic chiasm that usually will cause visual deficits seen on VF tests as a bitemporal hemianopsia

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26
Q

What is the visual field defect that typically results from a pituitary adenoma

A

Bitemporal hemianopsia

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27
Q

What kind of VF deficit will result from an internal carotid aneurysm

A

Binasal hemianopsia

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28
Q

Why does the an aneurysm on one ICA cause compression on both sides of the optic chiasm

A

It may compress the temporal fibers of the optic chiasm. In doing so, the optic chiasm is often displaced and compressed against the contralateral ICA, which in turn compresses the temporal fibers on that same side

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29
Q

This is a flat band that extends from the posterolateral corners of the optic chiasm to the LGN

A

Optic tract

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30
Q

90% of all fibers from the optic tract synapse where

A

LGN

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31
Q

10% of the fibers from the optic tract synapse where?

A

In other structures. The afferent pupillomotor reflex fibers will leave the optic tract before reaching the LGN and synapse in the pretectal nucleus of the midbrain

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32
Q

What kind of fibers are in each optic tract

A

Fibers from the temporal retina of the ipsilateral eye and fibers from the nasal retina of the contralateral eye

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33
Q

What kind of information do the temporal retinal fibers carry

A

Visual information regarding the nasal VF

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34
Q

What kind of information do the nasal retinal fibers carry

A

Visual information associated with the temporal VF

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35
Q

What is the VF deficit that would result from right optic tract transaction?

A

Left hemianopsia

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36
Q

Where is visual information from the optic tracts related

A

LGN

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37
Q

What is the largest and most important primary visual nucleus in humans

A

LGN

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38
Q

Where is the LGN located

A

In the dorsolateral aspect of the thalamus

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39
Q

This is a cone shaped structure that is multilaminar

A

LGN

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40
Q

LGN and layers

A

It is 6-layered, each layer containing the same type of cells. The retinal ganglion cells that project to a specific layer each have their own distinct characteristics

41
Q

The axons leaving the LGN are known as

A

Optic radiations

42
Q

How do the optic radiations course

A

Sweep laterally and inferiorly around the anterior tip of the temporal horns of the lateral ventricle.

43
Q

What optic radiations loop into the temporal lobe on their way to the occipital lobe

A

Meyers loop

44
Q

A lesion where would give you superior quandrantonopia (pie in the sky)?

A

Meyers loop (temporal lobe)

45
Q

What are the optic radiations that course through the parietal lobe called

A

Baum’s loop

46
Q

What forms the superior radiations

A

Fibers leaving the medial LGN

47
Q

What kind of information is carried in the Meyers loop?

A

Inferior retinal fibers (superior VF)

48
Q

What kind of information carried in Baum’s loop

A

Superior retinal fibers (inferior VF)

49
Q

What is another name for the primary visual cortex

A

V1 or Broadmann area 17

50
Q

Where is the primary visual cortex located

A

Predominantly on the medial surface of the occipital lobe with just a small bit extending around the posterior pole onto the lateral surface

51
Q

What divides the parietal lobes from the occipital lobes

A

The parieto-occipital sulcus

52
Q

What is the upper portion of the visual cortex

A

Cuneus

53
Q

What goes to the cuneus?

A

Superior retinal fibers (inferior VF)

54
Q

What is the lower part of the visual cortex

A

Lingual

55
Q

What goes to the lingual gyrus

A

Inferior retinal fibers (superior VF)

56
Q

What separates the cuneus and the lingual gyri

A

Calcarine sulcus

57
Q

Horizontal layers of the visual cortex

A

Most superficial is layer I and that which is most inward is layer VI. Each layer has a specific function

58
Q

What horizontal layer of the visual cortex contains the white myelinated fiber layer known as the strip of gennari?

A

Layer IV

This is where the term striate cortex comes from

59
Q

What is the striate cortex involved in

A

Binocular vision and contour analysis, which depend on both horizontal and vertical organization of the striate cortex

60
Q

Where do the superior optic radiations terminate?

A

In the striate cortex superior to the calcarine fissure (cuneus gyrus)

61
Q

Where do the inferior optic radiations terminate

A

In the striate cortex below the calcarine fissure (lingual gyrus)

62
Q

VF defect with lesion at cuneate gyrus

A

Contralteral lower quadrantonopia

63
Q

VF defect with lesion at lingual gyrus

A

Contralateral upper quadrantonopia

64
Q

What are the areas of higher visual association that analyze, recognize, and interpret environment?

A 
Area 18 (parastriate)
Area 19 (peristriate)
And others
65
Q

How are areas in one hemisphere connected to the other hemisphere

A

Posterior commissure

66
Q

Visual information is ultimately analyzed in the

A

Dominant parietal lobe

67
Q

What has to happen when visual information is analyzed in the dominant parietal lobe

A

Visual information arriving in the right occipital cortex must be passed through the corpus callosum to the left parietal lobe to the recognized and interpreted.

68
Q

Lesions of the left angular gyrus

A

Result in faulty integration of visual information despite intact primary visual pathway

69
Q

Gives rise to LMN supplying EOMs (levator palpebrae superioris, superior rectus, inferior rectus, medial rectus and inferior oblique)

A

Oculomotor nucleus

70
Q

Gives rise to preganglionic parasympathetic neurons to ultimately supply sphincter pupillae and ciliary muscles

A

EW nucleus

71
Q

Fives rise to LMN supplying EOMS (superior oblique)

A

Trochlear nucleus

72
Q

Gives rise to LMN supplying EOMS (lateral rectus )

A

Abducens nucleus

73
Q

Accommodative pathway

A
  • area 19 (visual association cortex) receives feedback from area 17 (primary visual cortex)
  • area 19 projects to pretectal nucleus
  • pretectal nucleus projects bilaterally to EW nucleus
  • preganglionic fibers synapse in the ciliary ganglion
  • postganglionic fibers supply the sphincter pupillae muscle to constrict the pupil and the ciliary muscle to thicken the lens
  • CNIII also carries out convergence of the eyes
74
Q

Accommodative triad

A

Accommodation
Pupillary constriction
Convergence

75
Q

Pupillary dilation pathway (sympathetic innervation)

A
  • post hypothalamus projects to intermediolateral cell column of the spinal cord at the upper thoracic levels
  • preganglionic fibers synapse onto postganglionic neurons in the superior cervical ganglion
  • postganglionic fibers form the ICA plexus and follow the ICA and its branches
  • postganglionic fibers supply the dilator pupillae muscles via the long ciliary nerve
76
Q

General schematics of primary visual pathway

A

Retina-optic nerve-chiasm-optic tract-LGN-optic radiations-visual cortex-visual association areas

77
Q

Retinal fibers and the horizontal raphe

A

They don’t cross over it

78
Q

Are peripheral or central retinal axons more superficial

A

Peripheral

79
Q

What si the organization of the retinal nerve fibers at the optic disc

A
  • inferonasal and inferotemporal take up 1/3
  • macular fibers take up 1/3
  • superonasal retinal fibers and superotemporal retinal fibers take up 1/3
80
Q

What is the anterior knee of Willbrand

A

At the chiasm, when the nasal fibers cross over, the inferior nasal fibers will shot straight over and kind of bend upward before going down into the contralteral tract

81
Q

What is the posterior knee of willbrand

A

The superior nasal fiber crossing the optic chiasm will go way down, almost into the ipsilateral optic tract and then come back up a little and shoot across the optic chiasm to contralateral tract

82
Q

What layers of the LGN do the magnocellular fibers synapse

A

Layers 1 and 2

83
Q

What layers of the LGN do the parvocellular fibers synapse in

A

Layers 3,4,6

84
Q

What layers of the LGN synapse ipsilateral fibers

A

2,3,5 same side

85
Q

What layers of the LGN synapse contralteral fibers

A

1,4,6

86
Q

Lesion of the left inferior optic radiations (Meyers loop)

A

Right homonomyous superior quadrantonopia (pie in the sky)

87
Q

Lesion of the superior optic radiation in the left parietal lobe (baums)

A

Right homonomyous inferior quadrantonopia

88
Q

PITS

A

Parietal inferior temporal superior (referring to VF not retinal fibers)

89
Q

Dorsal or parietal visual stream

A

Where

90
Q

Ventral or temporal stream

A

What

91
Q

Normal patient with the pupillary light reflex

A

Direct and consensual response to light shined in OD

92
Q

Afferent pupillary defect OD

A
  • No direct or consensual response to light shined in OD

- direct and consensual response to light shined OS

93
Q

Blood supply to central visual structures

A

Vertebrobasilar

94
Q

Difference between wet and dry AMD

A
  • dry is essentially drusen in Bruch’s layer
  • wet is where the RPE is sick, metabolic waste builds here, new vessels try to grow here from choroid and they are leaky
  • VEGF is what causes the new vessels to form
95
Q

Optic nerve transecting VF loss

A

Blindness in ipsilateral eye

96
Q

Optic tract transection VF loss

A

Contralteral hemianopsia

97
Q

Optic chiasm midsaggital transection

A

Bitemporal hemianopsia

98
Q

Horners syndrome

A
  • pupil constriction
  • ptosis
  • redness of skin
  • facial anhydrosis

Ocular Block 8 (6 decks)

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