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NE Exam 2 > Visual Tracts > Flashcards

Visual Tracts Flashcards

1
Q

Photoreceptors

A
  • Rods and Cones of Retina
  • Convert light waves into electrical impulses
  • Create visual image on the retina
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2
Q

3 Neuron Pathway in Primary Visual Cortex

A

(1) First Order Neurons: Bipolar cells of retina
(2) Second Order Neurons: Ganglion cells of retina; their axons converge at the optic disc and form the Optic Nerve
(3) Third Order Neurons: Located in Lateral Geniculate Body; axons terminate in primary visual cortex

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3
Q

Light from the top of an object gets reflected to the ___ part of the retina

A

Lower

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4
Q

Light form the bottom of an object gets reflected to the ___ part of the retina

A

Upper

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5
Q

The optics of the eyes are the reason why an object is seen ___ at the retina

A

Upside-down

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6
Q

Superior visual field is deflected towards the ___ retina

A

Inferior

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7
Q

Inferior visual field is deflected towards the ___ retina

A

Superior

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8
Q

Binocular Vision

A
  • Overlapping area in the center of visual fields
  • Brought to both cerebral hemispheres
  • Important for depth perception, stereoscopic vision
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9
Q

Monocular Blindness

A
  • Blindness in one eye
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10
Q

Hemianopia

A
  • ## Partial blindness/loss of sight in half of the visual field
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11
Q

Quadrantanopia

A
  • Partial blindness in a quadrant of visual field
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12
Q

Homonymous

A
  • Term used to describe lesions that occur after the optic chiasm
  • Losses of the same side (right or left)
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13
Q

Heteronymous

A
  • Losses at different sides of both eyes
  • Can be bitemporal or binasal
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14
Q

Macular Sparing

A
  • Loss of visual field with preserved center of the visual field (macula)
  • Caused by lesion to to primary visual cortex, PCA
  • Anastomosis between the MCA and PCA can result in homonymous hemianopia with preservation of macular function
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15
Q

Scotoma

A

Spot-like defect of visual field

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16
Q

What artery passes thru the Optic Canal with the Optic N (CN II)?

A

Ophthalamic A

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17
Q

Lesion of Optic N leads to:

A

Monocular blindness (Anopia)

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18
Q

Nasal fibers of the Optic N:

A

Cross at the Optic Chiasm

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19
Q

Temporal fibers of the Optic N:

A

Remain uncrossed (ipsilateral)

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20
Q

Lesion of the optic chiasm causes:

A

Heteronymous bitemporal hemianopia

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21
Q

What axons can be impacted by a tumor of the pituitary gland?

A

Nasal axons of the Optic N

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22
Q

Axons from the inferior retina cross ____ in the chiasm, where the superior nasal fibers cross ____ in the chiasm

A
  • anteriorly
  • posteriorly
23
Q

Unilateral lesion impinging on the anterior chiasm can give rise to:

A

Superior Temporal Contralateral Quadrantanopia

24
Q

Meningioma compressing the right optic N and anterior chiasm may result in a:

A

R central scotoma and a L superior temporal visual field defect (junctional scotoma) – due to involvement of the cross inferior nasal retinal fibers from the L eye

25
Q

Axons from the LGB form the:

A

Optic Radiations

26
Q

Optic Radiations

A
  • Originate in the LGB
  • Run along the temporal horn of the lateral ventricle approaching the anterior tip of the temporal lobe then run backwards thru the parietal lobe
  • Pass thru retrolenticular part of the internal capsule
  • LGB –> Temporal horn of lateral ventricle –> parietal lobe –> retrolenticular part of internal capsule –> occipital lobe
27
Q

Axons from superior retinal quadrants (inferior visual field) run thru the ___ lobe

A

Parietal

28
Q

Axons from the inferior retinal quadrants (superior visual field) run thru the ___ lobe

A

Temporal

29
Q

Meyer’s Loop

A

Loop formed by axons from lower retinal quadrants (superior visual field); located in temporal lobe

30
Q

Lesion of the Inferior optic radiations in the temporal lobe (Meyer’s Loop) result in:

A

Homonymous Superior Quadrantanopia

***Temporal produces Top quadrantanopia

31
Q

Lesion of the Superior optic radiations in the parietal lobe result in:

A

Lower Homonymous Quadrantanopia

32
Q

Disease affecting the posterior visual pathway (radiations or visual cortex) result in:

A

Scotomas that are extremely congrous (i.e same shape in each eye – this is b/c as nerve fibers travel back in the visual pathway they become more organized and perfectly aligned

33
Q

Blood supply of the Primary Visual Cortex V1 (Brodmann’s Area 17)

A

Mostly from the Posterior Cerebral A – Middle Cerebral A also contributes

34
Q

Primary Visual Cortex V1 (Brodmann’s Area 17)

A
  • Basic visual images are created here (color, shape, size of object)
  • Located predominantly on the medial surface of the hemisphere above and below the calcarine sulcus
35
Q

Contralateral nasal axons synapse in layers ___, ___, and ___ of the LGB

A

1, 4, 6

36
Q

Ipsilateral temporal axons synapse in layers ___, ___, and ___ of the LGB

A

2, 3, 5

37
Q

V1: Clinical Anastomosis

A
  • Anastomosis between PCA and MCA
  • Occlusion PCA -> homonymous hemianopia w/ macular sparing d/t MCA contribution
38
Q

Nerve fibers from macula (fovea) of retina occupy:

A
  • Posterior occipital tip of striate cortex
  • Larger area
39
Q

Nerve fibers from periphery occupy:

A
  • Anterior aspect of striate cortex
  • Smaller area
40
Q

Higher Order Visual Pathways: Ventral Stream

A
  • “What” area
  • Occipital lobe –> Parietal Lobe –> Frontal Lobe
  • Responsible for object recognition and storage of long-term visual information
41
Q

Higher Order Visual Pathways: Dorsal Stream

A
  • “Where” area
  • Occipital Lobe –> Temporal Lobe
  • Associated with the spatial location of objects and perception of motion
42
Q

Peripheral Rods, although not high in acuity, are particularly sensitive to:

A

Movement

43
Q

Ability to detect movement is central to the function of the:

A

Superior Colliculus

44
Q

Superior Colliculus

A
  • Detects movement
  • Receives visual information that has already been processed by the primary visual cortex
  • Involved in the control of two types of eye movements
45
Q

Two Types of Eye Movements that the Superior Colliculus controls:

A

(1) Saccades: rapid eye movements between fixation points
(2) Pursuit: slow movements that are used for tracking moving visual targets

46
Q

Pupillary Light Reflex

A

(1) Light shines in one eye and stimulates CN II
(2) Signal sent to Pretectal Area in Midbrain
(3) Projections sent bilaterally in Posterior Commissure to Edinger-Westphal Nuclei
(4) EWN sends preganglionic PS to CN III
(5) Ciliary Ganglion
(6) Postganglionic PS in short ciliary
(7) Sphincter Pupillae stimulated
(8) Bilateral pupil constriction

47
Q

Corneal (Blinking) Reflex

A

(1) Free nerve endings in Cornea detect touch
(2) CN V synapses in Trigeminal Sensory Nucleus and Spinal Trigeminal Nucleus
(3) Synapse bilaterally on CN VII motor nuclei
(4) Neuron in Facial N causes eye to blink

48
Q

Lesion of Optic Tract:

A

Homonymous Hemianopia

49
Q

Lesion of Optic Radiations from Superior Retinal Field:

A

Lower Homonymous Quadrantanopia

50
Q

Lesion of Optic Radiations from Inferior Retinal Field:

A

Upper Homonymous Quadrantanopia

51
Q

Blows to back of head or blockage occipital branches middle cerebral artery:

A

Loss of macular representation of visual fields

52
Q

Bilateral visual cortex lesions:

A

Cortical blindness

53
Q

Cortical Blindness

A

Patient can’t see but pupillary reflex is still intact

NE Exam 2 (19 decks)

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