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SHB - Exam 3 > VISUAL SYSTEM > Flashcards

VISUAL SYSTEM Flashcards

1
Q

What type of photoreceptor is most abundant at the FOVEA?

A

CONES

  • avascular region
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2
Q

Which photoreceptor is found on the peripheral part of the retina, is monolithic, transient, and for low light?

A

RODS

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3
Q

Where do axons of ganglion cells converge to form the optic nerve?

A

OPTIC DISK

  • blind spot
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4
Q

What is the visual pathway from the retina?

A
  1. Optic nerve
  2. Optic Chiasm
    ( nasal retina axons cross)
  3. Optic Tract
  4. Lateral Geniculate
  5. Optic Radiations
  6. Visual Cortex (occipital lobe)
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5
Q

Which parts of the retina cross? Which don’t? Which project medially? Laterally?

A
  1. TEMPORAL PORTIONS of retina DO NOT cross
    - medial vision
  2. Nasal portions cross
    - lateral vision
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6
Q

70% of the visual cortex comes from what region?

A

FOVEA

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7
Q 
Which cells have:
1. Large cell bodies
2. Dense DENDRITES
3. LARGE receptive fields
4. Rapidly adapting
5. respond best to MOVEMENT
Which photoreceptors are these cells composed of?
A

M-Type cells
(Magno-cellular)

  • RODS!!!

(M=man is color blind)

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8
Q

Which cells have:

  1. Small cell bodies
  2. short DENDRITES
  3. SMALL receptive fields
  4. more in FOVEA
  5. respond best to COLOR & FINE DETAIL

Which photoreceptors are these cells composed of?

A

P-Type
(Parvo-cellular)
-CONES!!!

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9
Q

Where does perception begin? Where else does information enter the brainstem?

A

Primary Visual Cortex
(AREA 17 in the Calcarene fissure of Occipital Lobe)

ALSO:

  1. Pretectal Area (pupillary light reflex)
  2. Superior Colliculus (head & neck movements –> descending MLF)
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10
Q

For optic radiations, where do upper fibers travel? Lower?

A

upper = PARIETAL

lower = TEMPORAL

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11
Q

Upper optic radiations end up at which visual field? lower?

A

Upper = INFERIOR

Lower = SUPERIOR

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12
Q

Which fibers makeup Meyer’s loop?

A

LOWER optic Radiations

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13
Q

If you cut the RIGHT optic nerve, what is the result?

A

RIGHT EYE blindness

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14
Q

If you cut the OPTIC CHIASM, what is the result?

A

TUNNEL VISION

  • Bilateral Hemianopeia
  • lateral (nasal) vision is not functioning
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15
Q

If you cut the RIGHT optic TRACT, what is the result?

A

Homonymous Hemianopia in the LEFT

lose temporal vision of LEFT eye, and RIGHT nasal vision of RIGHT eye

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16
Q

If you cut the RIGHT MEYER’s loop, what is the result?

A

(lower fibers = SUPERIOR vision)

Left Homonymous Superior Quadrantanopia (upper)

PIE IN THE SKY!!!

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17
Q

If you cut the RIGHT Lateral Geniculate fibers, what is the result?

A

same as cutting the optic tract

- LEFT homonymous Hemianopia
lose left temporal field, and right nasal field

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18
Q

If you partially lesion the RIGHT Optic Radiation fibers, what is the result?

A

LEFT Homonymous INFERIOR Quadrantinopeia

19
Q

If you lesion all the RIGHT Optic Radiation fibers (either stroke or car accident), what is the result?

A

Left Homonymous Hemianopeia with Macular Sparing

20
Q

What is the direct reflex and the consensual reflex?

A

Direct = light shone into LEFT eye so pupil constricts

Consensual = RIGHT pupil constricts as a result to the light in the left eye

21
Q

Why do both pupils constrict when light is shone into the Right eye?

A

Bilateral Connections to Edinger-Westphal nucleus by optic fibers

  • in SUPERIOR COLLICULUS & PRETECTAL area
22
Q

Which area is responsible for the pupillary right reflex?

A

PRETECTAL area

23
Q

If the RIGHT optic nerve (CN2) is damaged, and light is shown into this eye what is the result? What if light is shined into the eye without the lesion?

A

NEITHER PUPIL constricts

(direct response lacking and consensual)

BOTH PUPIL constrict when shine light into opposite eye (consensual response & direct response in tact)

24
Q

What is the result if light is shined into an eye with CN3 lesioned?

A

PUPIL in neither eye responds to the light (regardless of damaged eye)

25
Q

What are the sympots of Horner’s syndrome? What has been lesioned?

A
  1. Meiosis
  2. Ptosis
  3. Anhydrosis
  • lesion of Superior Cervical Ganglion
26
Q

What are the 3 results in changing gaze to focus on a nearby object?

A
  1. Vergeance of eyes (contract medial recti)
  2. Ciliary muscle constrict (lens thickens since tension released on zonulr fibers)
  3. Constriction of both pupils (to reduce light and improve optical performance)
27
Q

What is the corneal eye blink reflex mediated by?

A
  1. Free nerve endings in cornea
  2. Spinal Trigeminal (pain)Tract or Chief Sensory (touch)
  3. Interneurons
  4. Motor neurons in CN 7
  5. Orbicularis oculi
28
Q

What distributes information from each cornea during the CORNEAL BLINK REFLEX bilaterally to Facial Motor Neurons?

A

Reticular Formation Interneurons

(relay station)

  • eye blink is consensual = happen to both eye
29
Q

The corneal blink reflex directly involves with 2 cranial nerves?

A

CNV1 (ophthalmic division)

CN 7 - Orbicularis Oculi

(CN 8 also, since responding to loud sounds can cause us to blink, CN 3 = respond to bright light)

30
Q

Which layer of the primary visual cortex is most expanded?

A

IV

31
Q

What are the 3 specialized hyper columns and their main functions?

A
  1. Orientation –> spatial (vertical, horizontal perception)
  2. Blobs –> color specificity
  3. Occular DOminance - LEFT vs RIGHT
32
Q

Which cells are responsible for motion and spatial relationships or WHERE an object is?

A

MAGNOCELLULAR

33
Q

Which cells are responsible for depth and form, stationary objects & shapes?

A

PARVOCELLULAR cells

  • interblob = depth and form
  • blob = color sensitivity
34
Q

Which cortex (temporal or Parietal) is responsible for where an object is? What an object is?

A

Parietal (dorsal stream, non-color discriminative info) = WHERE

TEMPORAL (ventral stream from color & non) = WHAT AN OBJECT IS

35
Q

What are the 2 ways to detect motion o an object?

A
  1. Image moves temporally across retina (eye =stationary)

2. Head & eyes move to fix image on FOVEA

36
Q

Where is movements best represented?

A

Middle Temporal area of V5 (Medial Superior Temporal area)

37
Q

If the head is not moving, what kind of detection is used?

A

TEMPORAL

38
Q

How does the cortex perceive color?

A

Compares the differences in brightness & output, thus assigned a COLOR to that particular combo

39
Q

What kind of color cones are missing in the fovea?

A

BLUE

40
Q

How many cone systems does a human have?

A

3

Red
Bue
Green

41
Q 
On presentation to the emergency room, the pupillary light reflexes are tested on an unconscious patient.  The direct response to stimulation of the right eye is normal, as is the consensual response.  Both the direct and consensual responses are absent when light is shown in the left eye.  Where is the deficit in this patient?
Optic chiasm
Right optic tract
Left optic nerve
Left oculomotor nerve
Right calcarine sulcus
A

C) Left Optic N.

42
Q

A 79-year-old woman complains to her physician that she is having trouble seeing. She has no previous history of visual problems. Visual field examination reveals a right, superior quadrantanopia. Ophthalmoscopic examination shows no abnormalities with the optic disc, retinal vasculature or signs of retinal detachment. Which one of the following represents the most likely location of the lesion in this woman?

a) Left lateral geniculate nucleus (inferior quadrantinopea)
b) Left Meyer’s loop
c) Left calcarine gyrus
d) Right Meyer’s loop
e) Right optic tract

A

B) Left Meyer’s Loop

43
Q

. A visit to her physician confirms a partial visual loss, and MRI reveals a vascular lesion in the right hemisphere in the upper Calcarene sulcus. What deficits is the woman experiencing?

a) Left homonymous hemianopia
b) Left inferior quadrantanopia
c) Left superior quadrantanopia
d) Right inferior quadrantanopia
e) Right superior quadrantanopia

A

b) Left Inferior Quadrantanopia

SHB - Exam 3 (21 decks)

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