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Neuroscience > Lab 9 Structures > Flashcards

Lab 9 Structures Flashcards

1
Q

what is the visual field? what are the 2 parts?

A

what we “see”
* right/left fields for each eye

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2
Q

what is the retinal field? what are the 2 parts?

A

“flipped” version of what we see that’s projected onto retina of eye
* temporal field → lateral
* nasal field → medial

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3
Q

how does the information that falls on top/bottom of visual field reflect onto the retinal field?

A
  • objects within bottom of visual field fall on top of retinal field
  • objects within top of visual field fall on bottom of retinal field
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4
Q

how does info that falls on retinal field land on the primary visual cortex?

A
  • objects within bottom of retinal field will remain on bottom throughout course to visual cortex
  • objects within top of retinal field will remain on top throughout course to visual cortex
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5
Q

what information does optic nerve carry?

A

all visual field information from single eye

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6
Q

what happens if optic nerve is lesioned?

A

monocular info loss (all info from ipsilateral eye)

1 on diagram
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7
Q

where does info go after optic nerve? what info does it carry at this point?

A

optic chiasm
* visual info from nasal retina only crosses to other side

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8
Q

what happens if optic chiasm is lesioned?

A

heteronymous hemianopsia (bitemporal hemianopsia)

2 on diagram
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9
Q

where does the info go after the optic chiasm? what type of info does it carry at this point?

A

optic tract
* same visual field of each eye travels together via optic tract
* (ex.) left optic tract carries right sided visual field info from BOTH eyes
* (ex.) right optic tract carries left sided visual field info from BOTH eyes

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10
Q

what happens if optic tract is lesioned?

A

homonymous hemianopsia
* same visual field is affected for BOTH eyes

3 on diagram
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11
Q

where does the info go after the optic tract?

A

lateral geniculate nucleus (LGN)

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12
Q

what happens if optic radiation (LGN → primary visual cortex) is lesioned?

A

homonymous quadrantnopsia
parietal lobe → inferior quadrantnopsia
temporal lobe → superior quadrantnopsia (Meyer’s loop)
lesion in upper loop → lower visual field info from BOTH eyes lost
lesion in lower loop → upper visual field info from BOTH eyes lost

4 on diagram
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13
Q

what visual info terminates in upper portion of LGN?

A

visual field info carried from upper retina

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14
Q

what visual info terminates in lower portion of LGN?

A

visual field info carried from lower retina

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15
Q

what info is carried within given tract that travels between optic chiasm to LGN?

A

all aspects of visual info (peripheral, central, upper, lower)
* (ex.) left optic tract carries central vision, peripheral vision, upper and lower visual field info of right visual field of BOTH eyes
* (ex.) right optic tract carries central vision, peripheral vision, upper and lower visual field info of left visual field of BOTH eyes

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16
Q

where does info go after LGN?

A

visual info splits to take an upper and lower visual pathway to primary visual cortex in occipital lobe

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17
Q

where do the upper loop fibers travel? what info does it carry?

A

travels through parietal lobe → terminate in upper primary visual cortex (above calcarine sulcus)
* fibers carrying visual field info from upper RETINAL field (lower VISUAL field)

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18
Q

where do the lower loop fibers travel? what info does it carry?

A

travels through temporal lobe → terminate in lower primary visual cortex (below calcarine sulcus)
* fibers carrying visual field info from lower RETINAL field (upper VISUAL field)

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19
Q

how is visual info organized in primary visual cortex?

A

peripheral and central vision are represented in separate regions
* central vision dispersed over relatively large region

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20
Q

what is central vision sparing?

A
  • caused by focal/localized lesions in the visual cortex
  • since most of cortex associated with central vision is likely spared
21
Q

what happens if occipital lobe is lesioned?

A

homonymous quadrantnopsia with central vision spared

5 and 6 on diagram
22
Q

eye movement of CN III? if lesioned, what position does eye rest at?

A
  • up, down, in, up/in
  • if lesioned → out/down
23
Q

eye movement of CN IV? if lesioned, what position does eye rest at?

A
  • down/in
  • if lesioned → up/out
24
Q

eye movement of CN VI? if lesioned, what position does eye rest at?

A
  • lateral
  • if lesioned → medially
25
Q

lesion of eye movement cranial nerves leads to what type of vision?

A

double vision

26
Q

what is the name of the center that coordinates activation of conjugate gaze? what 2 main structures are included in it?

A

horizontal/pontine gaze center = abducnes nucleus + PPRF

27
Q

which gaze center is stimulated for the side you want to look at?

A

ipsilateral
* (ex.) left pontine gaze center activated → eyes move left

28
Q

which abducens nucleus is stimulated by the horizontal gaze center?

A

ipsilateral

29
Q

what happens once abducens nucleus is stimulated?

A

CN VI controls lateral rectus to move eye laterally

30
Q

which oculomotor nucleus is stimulated by the horizontal gaze center?

A

contralateral

31
Q

what happens once oculomotor nucleus is stimulated?

A

CN III controls medial rectus to move eye medially

32
Q

medial longitudinal fasciculus (MLF) connects what 2 structures?

A

highway for communication from abducens nucleus → contralateral oculomotor nucleus

33
Q

which way do eyes move in relation to gaze center?

A

eyes move toward activated gaze center (abducens nucleus)

34
Q

what 3 things can elicit conjugate gaze?

A
  • voluntary tracking (vision/interest) via cerebral cortex → smooth pursuit
  • head movement (vestibulo-ocular reflex)
  • moving object in visual field (optokinetic reflex) → finding/tracking
35
Q

how does voluntary tracking elicit conjugate gaze?

A

activation of frontal eye fields (Area 8) → stimulate contralateral abducens nucleus (PPRF) → conjugate gaze for voluntary tracking

36
Q

how does head movement elicit conjugate gaze?

A
  • semicircular canals elicits involuntary movement of eyes
  • semicircular canals stimulated → sends signals to medial/superior vestibular nucleus → stimulates contralateral abducens nucleus → involuntary conjugate gaze
  • vestibulo-ocular reflex stabilizes eyes for rapid turning/onset of head motion
37
Q

how does moving object in visual field elicit conjugate gaze?

A
  • optic nerve → optic tract → pretectal nucleus → medial vestibular nucleus → contralateral abducens nucleus
  • neurons in LGN, Area 17, middle/med sup temporal cortex can also be involved
  • optokinetic reflex: slower effect than vestibulo-ocular reflex but sustains stabilizing objects on retina for longer duration of head movement → picks up where vestibular system leaves off
38
Q

lesion of MLF

A
  • dysconjugate gaze: 2 eyes don’t move together
  • CN III and CN VI function intact
39
Q

lesion of CN III, CN VI, occulomotor nucleus

A
  • dysconjugate gaze: 2 eyes don’t move together
40
Q

what is the pupillary light reflex?

A

results in reflexive constriction of both pupils when light falls on one eye
* parasympathetic
* 2 pathways

41
Q

what is the pathway of the afferent limb of pupillary light reflex?

A

light enters eye → travels in optic nerve → ipsilateral pretectal nuclei → posterior commissure → connection to contralateral pretectal nuclei → Edinger-Westphal nuclei → bilateral response

42
Q

what is the pathway of the efferent limb of pupillary light reflex?

A

neurons exit Edinger-Westphal nuclei → travels towards eye alongside oculomotor nerve → ciliary ganglion (pre-ganglionic parasympathetics) → leaves ganglion → terminates in pupillary constrictor muscles of pupil (post-ganglionic parasympathetics)

43
Q

direct response to pupillary light reflex

A

constriction of pupil ipsilateral to pupil exposed to light

44
Q

consensual response to pupillary light reflex

A

constriction of pupil contralateral to pupil exposed to light

45
Q

what is the pupillary dilation (ciliospinal) reflex?

A

individual pupil dilation in darkened environment
* sympathetic
* separate pathway for each eye

46
Q

descending path of pupillary dilation reflex

A

light reduction signal → hypothalamic neuron → hypothalamus → intermediolateral cell column T1 segment → preganglionic sympathetic neuron → superior cervical ganglion

47
Q

ascending path of pupillary dilation reflex

A

post-ganglionc neuron from superior cervical ganglion (travels with internal carotid artery) → dilator muscle of pupil AND smooth muscle (Mueller’s muscle) of upper eyelid

48
Q

what is Horner’s Syndrome?

A

lesion of sympathetic path to head/neck

49
Q

what are the 3 signs/symptoms of Horner’s Syndrome?

A
  1. persistent pupillary constriction
  2. ptosis of upper eyelid
  3. loss of sweating on involved side of face

Neuroscience (9 decks)

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