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Neuro Anatomy > Week 5 Learning Issues > Flashcards

Week 5 Learning Issues Flashcards

1
Q

path of light to optic nerve

A

light -> photo receptors on retina -> ganglion cells (have axons that create optic nerve) -> optic nerve

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2
Q

fovea or area centralis

A

fovea (primates); area centralis (carnivores); region near central regina where photoreceptors are most densely packed for high acuity vision; area centrals is lateral and slightly dorsal to optic disc

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3
Q

horizontal streak

A

in horses and ruminants corresponding region of retina to area centralis is horizontal streak dorsal to optic disk

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4
Q

receptive field of visual neuron

A

region of visual field from which light will produce active in a neuron

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5
Q

activaty in visual neuron

A

interpreted by brain as indication of visual stimulus in taat neuron’s visual receptive field

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6
Q

activity in visual neuron represents

A

a visual stimulus in that neuron’s receptive field

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7
Q

fixation point

A

place in visual field at which one is “looking”; convergence of eyes causes this location in visual field to be represented at corresponding its on each central retina (ie fovea or area centralis) permitting visual stimuli at fixation point to be analyzed by the most densely packed photoreceptors on retina for highest visual acuity

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8
Q

optic chiasm

A

sits just rostral to hypophysis at junction of rostral and middle cranial fossae more than half of axons coming from each retina cross to enter the contralateral optic tract while rest of the axons enter ipsilateral optic tract

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9
Q

where do axons of in optic tract synapse?

A
  1. Lateral Geniculate Nucleus
  2. Pretectal Nuclei
  3. Rostral Colliculus
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10
Q

primary visual cortex

A

in the occipital lobe; receives information from lateral geniculate nucleus via thalamic relay; axons travel from LGN to occipital lobe via optic radiations

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11
Q

association areas

A

visual info sent from primary visual cortex to association areas in parietal and temporal lobes for more complex visual processing

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12
Q

Retino-Geniculo-COrtical visual pathway responsible for

A

pathway from retina to visual cortical areas, essential for conscious visual perception; in context of neurological exam it is required for menace response, visual following, and visual placing

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13
Q

visual field

A

area of world seen by the eyes when they are a given position;

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14
Q

visual field in animals with more laterally placed eyes

A

larger

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15
Q

right and left visual hemifields

A

specific the regions of the visual field to right or left of the vertical meridian

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16
Q

temporal hemiretina

A

half of the retina closest to the temple; can see binocular zone of contralateral visual hemifield

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17
Q

nasal hemiretina

A

half of the retina closest to the nose; sees all of ipsilateral visual hemifield

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18
Q

retinotopic representation

A

spatial relationships between locations in visual field are maintained in spatial relationships of the retinal neurons that represent that location. When the retinal ganglion cells project to neurons in LGN and rostral colliculus, the spatial relationship of the neurons is maintained such that LGN and rostral colliculus contain “retinotopic” maps of visual field; means that adjacent neurons within these nuclei represent adjacent regions of the visual field; this is maintained in pathway to visual cortex

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19
Q

animals with frontal eyes

A
  • larger binocular zone

- smaller visual field

20
Q

animals with lateral eyes

A
  • smaller binocular zone
  • larger visual field
  • more axons cross in chiasma
21
Q

binocular zone

A

central visual field that is seen by both eyes; this region is the best at depth perception

22
Q

axons from ganglion cells in either temporal hemiretina

A

travel along optic nerve and optic tract to LGN, Rostral Colliculus and Pretectal Nuclei on ipsilateral side of brain

23
Q

axons from ganglion cells in either nasal hemiretina

A

cross at optic chiasma and continue in the contralateral optic tract to contralateral LGN, Rostral Colliculus, and Pretectal Nuclei; Each LGN then projects via internal capsule to ipsilateral primary visual cortex in occipital lobe (ipsilateral to LGN not to eye visual stimuli originally entered through)

24
Q

PLR is not

A

a test of vision bc it is a reflex response mediated by brainstem circuitry

25
Q

any lesion beyond optic chiams

A

knocks out entire contralateral visual hemifield

26
Q

optic chiasm desication and eye position

A

the more lateral the eyes the more axons that decussate in optic chiasm

27
Q

most common component tested by menace response

A

most commonly medial (nasal) hemiretina of each eye is tested by menacing from the visual hemifield on the same side as the stimulated eye

28
Q

lesion of one eyeball, retina, or optic nerve

A

may cause a deficit in the menace response to stimuli directed at eye on the side of lesion

29
Q

lesion of optic tract, LGN, optic radiations, or cerebral cortex

A

may cause deficit in menace response to stimuli coming from visual hemifield contralateral to the lesion

30
Q

lesion affecting cerebellum and facial nuclei or nerves

A

can produce deficits in mince response

31
Q

loss of one eye or damage to optic nerve on one side will result in

A

loss of vision in peripheral, monocular zone of ipsilateral visual hemifield (visual hemifield ipsilateral to the lesion); animal will still be able to see the central region of ipsilateral visual hemifield as well as entire contralateral visual hemifield with remaining eye

32
Q

loss of one eye or damage to optic nerve on one side will result in PLR

A

no direct or consensual PLR when light is shined in damaged eye, but direct and consensual PLR will be normal when light is shined in other eye

33
Q

loss of one eye or damage to optic nerve on one side will result in, menace

A

menace response will be absent when stimulus is directed at the eye on the affected side

34
Q

lesion interrupting fibers that cross at optic chiasm

A

would produce loss of peripheral vision in both hemifields; more dramatic in animals with laterally placed eyes bc higher percentage of retinal axons cross in these species

35
Q

lesion interrupting fibers that cross at optic chiasm PLR

A

little/ no deficit in PLR bc pretectal nuclei will still receive input form non-crossing retinal axons

36
Q

lesion interrupting fibers that cross at optic chiasm, menace

A

menace would be compromised for stimuli directed at nasal hemiretina of both eyes

37
Q

lesion of retino-geniculo-cortical pathway beyond chiasm (ie optic tract, LGN, optic radiations, or visual cortex)

A

will result in loss of conscious vision in contralateral visual hemifield

38
Q

lesion of retino-geniculo-cortical pathway beyond chiasm (ie optic tract, LGN, optic radiations, or visual cortex) menace

A

menace will be absent when contralateral eye is stimulated (when you stimulate nasal hemiretina of eye contralateral to the lesion) until you hit cerebellum then ipsilateral representation again

39
Q

lesion of retino-geniculo-cortical pathway beyond chiasm (ie optic tract, LGN, optic radiations, or visual cortex) PLR

A

don’t usually produce PLR deficit bc pretectal nuclei project bilaterally onto parasympathetic nucleus CN III so long as PTN on one side of brain receives visual input PLR would be intact

40
Q

lesions beyond optic tract/ LGN PLR

A

should not produce deficit in PLR

41
Q

menace response pathway (starting L nasal hemiretina)

A
  1. L nasal hemiretina
  2. L Optic Nerve
  3. Optic Chiasm
  4. Optic Tract
  5. LGN
  6. Internal capusle
  7. R occipital lobe
  8. Parietal and motor cortex
  9. Pontine nuclei
  10. Middle cerebellar peduncle
  11. Cerebellum
  12. Facial nuclei in medulla
  13. Facial nerve
  14. Orbicularis oculi muscles
42
Q

retino-geniculo-coritical pathway

A
  1. Retina
  2. Optic Nerve
  3. Optic Chiasm
  4. Optic Tract
  5. LGN (thalamus)
  6. Optic radiations (w/ in internal capsule)
  7. primary visual cortex (occipital lobe)
  8. Cortical association areas (parietal and temporal lobes)
43
Q

parietal lobe

A

role in visuomotor transformations

44
Q

temporal lobe

A

role in visual recognition

45
Q

retiono-geniculo-cortical pathway needed for

A

menace response, visual following, visual placing

PLR unaffected by this pathway

Neuro Anatomy (17 decks)

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