Visual Tracts

Question 1

Photoreceptors

Answer 1

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

Question 2

3 Neuron Pathway in Primary Visual Cortex

Answer 2

(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

Question 3

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

Answer 3

Lower

Question 4

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

Answer 4

Upper

Question 5

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

Answer 5

Upside-down

Question 6

Superior visual field is deflected towards the ___ retina

Answer 6

Inferior

Question 7

Inferior visual field is deflected towards the ___ retina

Answer 7

Superior

Question 8

Binocular Vision

Answer 8

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

Question 9

Monocular Blindness

Answer 9

• Blindness in one eye

Question 10

Hemianopia

Answer 10

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

Question 11

Quadrantanopia

Answer 11

• Partial blindness in a quadrant of visual field

Question 12

Homonymous

Answer 12

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

Question 13

Heteronymous

Answer 13

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

Question 14

Macular Sparing

Answer 14

• 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

Question 15

Scotoma

Answer 15

Spot-like defect of visual field

Question 16

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

Answer 16

Ophthalamic A

Question 17

Lesion of Optic N leads to:

Answer 17

Monocular blindness (Anopia)

Question 18

Nasal fibers of the Optic N:

Answer 18

Cross at the Optic Chiasm

Question 19

Temporal fibers of the Optic N:

Answer 19

Remain uncrossed (ipsilateral)

Question 20

Lesion of the optic chiasm causes:

Answer 20

Heteronymous bitemporal hemianopia

Question 21

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

Answer 21

Nasal axons of the Optic N

Question 22

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

Answer 22

• anteriorly
• posteriorly

Question 23

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

Answer 23

Superior Temporal Contralateral Quadrantanopia

Question 24

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

Answer 24

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

Question 25

Axons from the LGB form the:

Answer 25

Optic Radiations

Question 26

Optic Radiations

Answer 26

- 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

Question 27

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

Answer 27

Parietal

Question 28

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

Answer 28

Temporal

Question 29

Meyer's Loop

Answer 29

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

Question 30

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

Answer 30

Homonymous Superior Quadrantanopia ***Temporal produces Top quadrantanopia

Question 31

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

Answer 31

Lower Homonymous Quadrantanopia

Question 32

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

Answer 32

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

Question 33

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

Answer 33

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

Question 34

Primary Visual Cortex V1 (Brodmann's Area 17)

Answer 34

- 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

Question 35

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

Answer 35

1, 4, 6

Question 36

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

Answer 36

2, 3, 5

Question 37

V1: Clinical Anastomosis

Answer 37

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

Question 38

Nerve fibers from macula (fovea) of retina occupy:

Answer 38

- Posterior occipital tip of striate cortex - Larger area

Question 39

Nerve fibers from periphery occupy:

Answer 39

- Anterior aspect of striate cortex - Smaller area

Question 40

Higher Order Visual Pathways: Ventral Stream

Answer 40

- "What" area - Occipital lobe --> Parietal Lobe --> Frontal Lobe - Responsible for object recognition and storage of long-term visual information

Question 41

Higher Order Visual Pathways: Dorsal Stream

Answer 41

- "Where" area - Occipital Lobe --> Temporal Lobe - Associated with the spatial location of objects and perception of motion

Question 42

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

Answer 42

Movement

Question 43

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

Answer 43

Superior Colliculus

Question 44

Superior Colliculus

Answer 44

- 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

Question 45

Two Types of Eye Movements that the Superior Colliculus controls:

Answer 45

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

Question 46

Pupillary Light Reflex

Answer 46

(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

Question 47

Corneal (Blinking) Reflex

Answer 47

(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

Question 48

Lesion of Optic Tract:

Answer 48

Homonymous Hemianopia

Question 49

Lesion of Optic Radiations from Superior Retinal Field:

Answer 49

Lower Homonymous Quadrantanopia

Question 50

Lesion of Optic Radiations from Inferior Retinal Field:

Answer 50

Upper Homonymous Quadrantanopia

Question 51

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

Answer 51

Loss of macular representation of visual fields

Question 52

Bilateral visual cortex lesions:

Answer 52

Cortical blindness

Question 53

Cortical Blindness

Answer 53

Patient can't see but pupillary reflex is still intact