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Neuroscience III (Sara) > Visual System & Diencephalon > Flashcards

Visual System & Diencephalon Flashcards

1
Q

Retina

A

-Neural element of the eye

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2
Q

Fovea

A
  • Point of fixation
  • Highest visual acuity
  • Highest concentration of cones
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3
Q

Rods and Cones

A
  • Rods = more peripheral

- Cones = more central

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4
Q

When optic nerve leaves retina, it is

A

Visual blind spot

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5
Q

Visual field

A
  • What each eye sees

- Visual fields overlap ~60% of the time

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6
Q

Explain the visual field pathway

A

Light from the TEMPORAL visual field falls on the NASAL retina & light from the NASAL visual field falls on the TEMPORAL retina
-CN II fibers from nasal retina cross in optic chiasm so fibers of optic tract and radiation carry info about the contralateral visual field

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7
Q

Lateral geniculate nucleus

A

Relay nucleus of the thalamus

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8
Q

Optic Radiations

A
  • -Fibers that arise from lateral geniculate nucleus
  • Travel to the cortex
  • Retintopically organized so superior fibers represent inferior part of visual field and Meyer’s loop represents superior part of visual field
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9
Q

Visual Cortex

A
  • Area 17 - primary visual cortex

- Area 18 and 19 - visual association cortices

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10
Q

Hemianopia

A

Loss of half of visual field

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11
Q

Quadranopia

A

Loss of one quadrant of visual field

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12
Q

Homonymous

A

Refers to overlapping visual fields

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13
Q

Heteronymous

A

Refers to non-overlapping field from each eye

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14
Q

Retina or optic nerve lesion

A

Blindness in same side of lesion

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15
Q

Medial optic chiasm lesion

A

Bilateral temporal hemianopia

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16
Q

Lateral optic chiasm lesion

A

Same sided medial/nasal hemianopia

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17
Q

Optic radiation lesion

A
  • Most common visual field loss

- Homonymous Hemianopia - loss of nasal portion of same side and temporal portion of opposite side

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18
Q

Meyer’s Loop lesion

A

Opposite sided homonymous superior quadranopia

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19
Q

Superior optic radiation lesion

A

Opposite sided Homonymous inferior quadrinopia

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20
Q

Occipital lobe lesion

A

Cortical blindeness

21
Q

Superior Colliculus Inputs

A
  • Direct from retina and area 17

- Receives somatosensory and auditory input

22
Q

Superior Colliculus Projection

A
  • Reticular formation to generate saccades

- Cervical spinal cord via tectospinal tract to orient head

23
Q

Superior Colliculus Function

A

Orient head and eyes to visual, somatosensory, and auditory stimulus

24
Q

Superior Colliculus Lesion

A

Inability to orient to contralateral visual system

25
Retinohypothalamic fibers
- Directly from retina | - Influences circadian rhythms and cycles
26
Pupillary Light Reflex
- Tests integrity of connection between diencephalon/retina and midbrain - Requires CN II and CN III - Retina --> CN II --> midbrain --> CN III --> Direct & Consensual responses
27
Direct and Consensual responses
- Direct = shine light in eye and pupil constricts | - Consensual = shine light in eye and pupil in opposite eye also constricts
28
Information after Occipital Cortex
Occipital cortex (area 17) --> area 18 & 19 --> dorsal stream (motor control) or ventral stream (conscious awareness of visual experience)
29
Dorsal stream "Where"
- TO posterior parietal cortex - Ambient vision - Operates on information from fovea & retinal periphery - Information used to guide actions - Information about object characteristics
30
Ventral stream "What"
- To inferotemporal cortex - Focal vision - Depends on information from fovea - Conscious perceptual experience of vision - Recognition of objects
31
Ventral & Dorsal stream Lesions
- Ventral: Visual Agnosia | - Dorsal: Optical Ataxia
32
4 parts of diencephalon
1. Epithalamus 2. Subthalamus 3. Hypothalamus 4. Thalamus
33
Thalamus
- Comprises 80% of diencephalon - Almost all sensory pathways relay in thalamus - Motor from Cb and BG - Input from limbic areas - Relay information to cortex - through VA and VL - Receive feedback information from cortex which they project
34
Ventral anterior (VA)/Ventral lateral (VL)
- Afferents: BG & Cb | - Efferents: Supplemental and premotor motor areas
35
VPL
- Afferents: DCML, spinothalamic tracts | - Efferents: Area 3, 1, 2; primary somatosensory cortex
36
VPM
- Afferents: Trigeminal system | - Efferents: Area 3, 1, 2; primary somatosensory cortex
37
Lateral Geniculate
- Afferents: Optic tract | - Efferents: Area 17 - primary visual cortex
38
Medial Geniculate
- Afferents: Brainstem auditory tract | - Efferents: Area 41, primary auditory cortex
39
Intralaminar nuclei
- Afferents: Spinothalamic/RF/ARAS (ascending reticular activating system) - Efferents: All areas of cortex, striatum
40
Internal capsule
Between thalamus and caudate (medial) and lentiform nucleus (lateral)
41
Anterior limb of internal capsule
- Between lenticular nucleus and head of caudate | - Carries fibers to frontal cortex from limbic portions of thalamus
42
Posterior limb of internal capsule
- Between lenticular nucleus and thalamus | - Ascending motor and sensory fibers (VA, VL (BG & CB), VPL, VPM) and descending corticobulbar and corticospinal fibers
43
Genu of internal capsule
Between anterior and posterior limbs
44
Retrolenticular portion of internal capsule
Optic radiations
45
Sublenticular portion of internal capsule
Remainder of optic radiations
46
Posterior Limb Internal Capsule Stroke
- Hemiparesis and hemianesthesia - NO COGNITIVE deficits - Contralateral pure motor hemiplegia; contralateral pure hemi-sensory syndrome, contralateral homonymous hemianopia
47
Blood supply of Internal Capsule
Lenticulostriate arteries - penetrating branches of mostly middle cerebral artery
48
Smaller area posterior limb internal capsule stroke
Dysarthria and clumsy hand

Neuroscience III (Sara) (4 decks)

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