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PART ONE REVISION. > VISION - Visual Pathway > Flashcards

VISION - Visual Pathway Flashcards

1
Q

What defect produces a junctional scotoma defect?

A

Defect in optic nerve near optic chiasm at wilbrands knee –> nasal fibres decussate and bend upwards towards opposte optic and get affected

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2
Q

What field is produced with a central optic chiasm defect?

A

Leads to bitemporal hemianopia (both nasal fibres are affected)
Bitemporal hemianoic paralysis of the pupillary response

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3
Q

What is the visual pathway? (7)

A
  1. Retina
  2. Optic nerve
  3. Optic chiasm
  4. Optic tract
  5. Lateral geniculate body
  6. Optic radiations
  7. Visual cortex
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4
Q

What are the causes of a central optic chiasm lesion (5)

A
  1. Craniopharyngioma
  2. Pituitary tumor
  3. Suprasellar aneurysm
  4. Supresellar meningioma
  5. Third ventricular dilatation due to hydrocephalus
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5
Q

What happens following an optic tract lesion to the fibres? What visual defect?

A

uncrossed temporal fibres lead to nasal defect in ipsilateral eye and crossed nasal fibres lead to temporal defect in opposite eye - homonymous hemianopia

Can cause a third nerve palsy and ipsilateral hemiplegia

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5
Q

What is the outcome of a lateral optic chiasm defect

A

Affects temporal fibres of optic chiasm –> nasal defect
Binasal hemianopia
Binasal hemianopic paralysis of pupillary reflex

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5
Q

What are the main causes of optic tract lesions? (5)

A
  1. Thalamus tumours
  2. Syphilitic meningitis
  3. TB
  4. Posterior cerebral artery aneurysm
  5. Superior cerebellar artery aneurysm
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6
Q

What visual defect is produced with a lateral geniculate body lesions? Pupillary response is present or absent?

A

Homonymous hemianopia with sparing of pupillary reflex as the pupillary fibres have already left the optic tract at the superior folliculus

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7
Q

What visual defect is produced from a lesion in Meyer’s loop (inferior retinal fibres in optic radiation travelling in temporal lobe)

A

Homonymous superior temporal quadrantinopia (pie in the sky)

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8
Q

What visual field defect is produced from a lesion in superior retinal fibres from optic radiations?

A

Homonymous inferior temporal quadrantinopia (pie in the floor)
–> fibres pass through parietal lobe

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9
Q

What is the blood supply of the visual cortex?

A

Posterior cerebral artery
Middle cerebral artery

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10
Q

What visual field lesion is seen in a visual cortex lesion (PCA /MCA stroke)

A

Congruous Homonymous hemianopia with macular sparing (macular spared as receives dual supply from PCA or MCA)

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11
Q

What conditions can affect the first order neurons in the sympathetic pathway in Horner’s syndrome (hypothalamus to spinal centre of budge)

A
  1. CVA
  2. Lateral medullary syndrome
  3. Multiple sclerosis
  4. Neurological disorders and infections
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12
Q

What conditions can affect the second order (preganglionic neurons) from ciliospinal centre of budge to superior cervical ganglion in sympahetic pathway (Horner’s syndrome)

A

Any disease affecting mediastinum and neck
1. Apex lung lesions - Pancoast
2. Subclavian artery injury
3. Brachial plexus injury
4. Mediastinal lymphadenopathy
5. Dental abscess involving mandibular region

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13
Q

What diseases can affect the third order (Superior cervical ganglion to long ciliary nerves) in Horner’s syndrome

A
  1. Carotid cavernous fistula
  2. Carotid artery dissection/aneurysm
  3. Raeder paratrigeminal system
  4. Herpes zoster infection
  5. Temporal arteritis
  6. Cluster headaches or migraines
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14
Q

What is the reason for partial ptosis or reverse/inverse ptosis in Horner’s syndrome?

A
  1. Symphathetic chain supplies superior tarsal plate, responsible for partial elevation of eyelid
  2. Sympathetic chain supplies lower eyelid - lesions leads to upward movement of lower eyelid
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15
Q

What happens to the pupil in Horner’s syndrome?

A

Smaller than other side
Pupillary and accomodation reflex is intact as they are not reliant on sympathetic nerve supply

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16
Q

Right sided visual field is present in which side of the visual pathway?

A

Left side (contralateral)

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17
Q

Nasal fields go on which side of the retina? Nasal or temporal?

A

temporal

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18
Q

Nasal fibres carry which visual field? nasal or temporal?

A

temporal.

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19
Q

Which fibres dessucate in the optic chiasm?

A

The NASAL fibres.

20
Q

Which fibres are carried in the optic tract?

A
  1. Uncrossed (ipislateral) temporal fibres carrying nasal visual field information
  2. crossed (contralateral) nasal fibres carrying temporal visual field information
21
Q

Where is the optic chiasm located?
Superior -
Posterior -
Medial -
Betweeen…

A

superior: the pituitary gland
inferior: lamina terminalis (medial wall of forebrain)
posterior: anterior cerebral arteries and anterior communicating artery
medial: internal carotid and cavernous sinus

between antierior wall and fall of third ventricle

22
Q

How big is the optic chiasm?

A

12mm x 8mm

23
Q

Where do the fibres from the LGN go to?

What is the difference in route between the superior and inferior visual field fibres from LGN?

A

Optic radiations into the calcarine fissure in visual cortex

  1. superior visual field: inferior horn of lateral ventricle (MEYER’S LOOP) and travel towards calcarine fissure –> carry impulses from superior visual field.
  2. inferior visual field: travel in parietal lobe and enter into calcarine fissure of visual cortex (BAUM’S LOOP)
24
Q

What are the components of the visual cortex?

A
  1. Primary visual cortex (Broadmann’s area number 17)
  2. Secondary visual cortex
  3. Ventral stream (inferotemporal area)
  4. Dorsal stream (Posterior partial area)
25
Q

What is the ventral stream responsible for?

A

WHAT? of the object - shape, colour

26
Q

Whatis the dorsal stream responsible for?

A

The WHERE of the object

27
Q

What is the order of neurons in the visual pathway?

A
  1. Rod’s and Cones (1st Order)
  2. Bipolar Cells (2nd Order)
  3. Ganglion cells (3rd Order)
  4. LGB (4th Order)
28
Q

What is the role of the pulvinar nucleus?

A

visual attention and motor integration

29
Q

What is the role of the suprachiasmatic nucleus?

A

circadium rhythm

30
Q

What is the role of the pretectal nucleus?

A

pupillary light reflex —-> some fibres break off before reaching LGN and synapse at pretectal nucleus –> pass to edinger westphal nucleus on ipsilateral and contralateral sides –> parasympathetic fibres to CG –> postganglionic fibres travel in short ciliary nerves to constrictor pupillae

31
Q

What is the role of the superior colliculus? (5)

A
  1. visual grasp reflex
  2. automatic scanning of images
  3. visual attention
  4. co-ordination of head/eye movements
  5. auditory/visual association pathways.
32
Q

What is are the two routes of the optic nerve after the optic chiasm?

A

optic tracts —-> lateral geniculate body —-> optic radiation —> terminate at Brodmann area 17 of visual cortex

some fibres bypass LGB and terminate in either:
1) pretectal nucleus (pupillary light reflex)
2) superior colliculus (regulaton of saccadic eye movements)

33
Q

What is are the two routes of the optic nerve after the optic chiasm?

A

optic tracts —-> lateral geniculate body —-> optic radiation —> terminate at Brodmann area 17 of visual cortex

some fibres bypass LGB and terminate in either:
1) pretectal nucleus (pupillary light reflex)
2) superior colliculus (regulaton of saccadic eye movements)

34
Q

Where is inferior visual field information carried in the optic tract?

A

superior retinal fibres - branch around parietal lobe into visual cortex.

35
Q

Where is superior visual field information carried in optic tract?

A

inferior retinal fibers branch around temporal lobe (meyer’s loop)

36
Q

How many layers are there in the LGN?

A

6

37
Q
A
38
Q

What are the layers of optic radiations?

A

1, 4, 6 - contralateral fibres synapse
2, 3, 5 - ipsilateral fibres synapse

39
Q

What type of retinal information is relayed in layers 1-2 of the LGN? Via which pathway?

A

peripheral retinal information - transferred via magnocellular pathway.

40
Q

What type of retinal information is relayed in layers 3-6 of the LGN? Via which pathway?

A

information from fovea, transmitted by parvocellular pathway

41
Q

What are optic radiations? Where do their cell bodies lie? Where do they terminate?

A

Nerve fibre bundles whos cell bodies lie in the LGN and terminate in striate visual corte (area 17)

42
Q

macula information passes directly or widely in optic radiations?

peripheral information is transmitted directly or widely in optic radiations?

A

macula - directly
peripheral - widely.

43
Q

Where does macula information enter the visual cortex?

Where does peripheral information enter the visual cortex?

A

macula - posterior 1/3rd of visual cortex
peripheral - anteriorly.

44
Q

How many layers are there in the visual cortex?

A

6

45
Q

What is the function of layer 2 of the visual cortex?

A

contains cells which synapse with contralateral visual cortex via corpus callosum. Projects to secondary visual cortex.

46
Q

What is the functon of layer 4 (thickest layer) of the visual cortex?

A

receives efferents from LGN and contains stellate cells. It contains fibres from the macula.

47
Q

What is the function of layer 5 of the visual cortex?

A

Relays information to the superior colliculus which connects to MLF which allows ocular movements to be co-ordinated with flashes of light.

48
Q

What is the function of layer 6 of the visual cortex?

A

relays information to the LGN (feed-forward) and contains mostly pyramidal cells.

49
Q

Whats the difference between magnocellular vs parvocellular fibres? 1. Velocity, 2. Type, 3. Location, 4. Length of response.

A
  1. Velocity - Magno fast, parvo slow
  2. Type - Magno - light detection fibres ;
    Parvo - foveal/parafoveal and spatial discrimination fibres
  3. Location - Magno - Layers 1 & 2 of LGN
    - Parvo - Layers 3-6 of LGN
  4. Length of response - Magno - transient, Parvo - sustained

PART ONE REVISION. (84 decks)

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