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MD1 Neuroscience > Visual Pathway > Flashcards

Visual Pathway Flashcards

1
Q

What kind of glutamate receptors can bipolar cells express?

A

Metabotropic

Ionotropic

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2
Q

Why are there different types of ganglion cells?

A

Each type provides info for different stream of vision

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3
Q

What are two types of ganglion cells?

A

M/parasol

P/midget

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4
Q

Are M and P ganglion cells ON or OFF ganglion cells?

A

Each type has ON and OFF type

  • M ON
  • M OFF
  • P ON
  • P OFF
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5
Q

Describe M ganglion cells

A 
Motion
Large cell bodies
Long processes
Covers large area of retina
10-15% of ganglion cells
Especially prone to disease
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6
Q

Describe P ganglion cells

A 
Colour vision
Visual acuity
Small cell bodies
Short processes
80% of ganglion cells
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7
Q

What are the targets of ganglion cell axons?

A 
Lateral geniculate nucleus (LGN) in thalams
Pretectum in midbrain
Suprachiasmatic nucleus in hypothalamus
Superior colliculus
Various other nuclei of thalamus
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8
Q

Why do ganglion cell axons project to the LGN?

A

Major target of most ganglion cells

Visual pathway

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9
Q

Why do ganglion cell axons project to the pretectum?

A

Pupil responses

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10
Q

Why do ganglion cell axons project to the suprachiasmatic nucleus?

A

Circadian rhythm

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11
Q

Why do ganglion cell axons project to the superior colliculus?

A

Eye movements

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12
Q

Why do ganglion cell axons project to the nuclei in the thalamus other than the LGN?

A

Photophobia

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13
Q

What is the optic chiasm?

A

Fibres from right and left optic nerves combine

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14
Q

How many ganglion fibres cross at the optic chiasm?

A

Half

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15
Q

Where is the optic chiasm?

A

Base of brain anterior to pituitary

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16
Q

From which hemifield does the nasal retina receive light information?

A

Temporal hemifield

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17
Q

From which hemifield does the temporal retina receive light information?

A

Nasal hemifield

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18
Q

Which fibres cross at the optic chiasm?

A

Nasal fibres

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19
Q

Which hemisphere views each hemifield?

A

Right visual hemifield viewed by left hemisphere

Left visual hemifield viewed by right hemisphere

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20
Q

What part of the visual field does a stroke affect when it’s in the visual cortex?

A

Half of each field in each eye, rather than one entire eye

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21
Q

What is the name of the tract after the optic chiasm?

A

Optic tract

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22
Q

Where do ganglion cell axons in the optic tract synapse?

A

LGN

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23
Q

How many neurons are there in the visual pathway?

A

2

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24
Q

Why is the anatomical position of the optic chiasm relevant to pathology?

A

Pituitary gland just below

Condition affecting it can affect chiasm; eg: in pituitary macroadenoma

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25
Q

What is the classic presentation of a person’s visual field when they have a pituitary macroadenoma?

A

Bitemporal hemianopia

26
Q

Which hemifields are affected in bitemporal hemianopia?

A

Temporal hemifields

27
Q

Where do second order neurons in the visual pathway arise from?

A

LGN

28
Q

How is information in the LGN segregated?

A

By eye and ganglion cell type

29
Q

How many layers are there in the LGN?

A

6

30
Q

What are the types of cells in the LGN?

A

Magnocellular

Parvocellular

31
Q

Where do M ganglion cells synapse?

A

Magnocellular layers: 1 and 2

32
Q

Where do P ganglion cells synapse?

A

Parvocellular layers: 3-6

33
Q

Which layers receive input from the right eye?

A

2, 3, 5

34
Q

Which layers receive input from the left eye?

A

1, 4, 6

35
Q

Where do LGN neurons project to?

A

Primary visual cortex (V1)

36
Q

What is the Broddman’s area of V1?

A

Area 17

37
Q

Where in the brain is the primary visual cortex?

A

Occipital lobe around calcarine fissure

  • On medial aspect
  • Upper and lower banks around fissure
38
Q

How is information organised in the primary visual cortex?

A

Retinotopic organisation = neighbouring cells within retina project to neighbouring cells in LGN and visual cortex

39
Q

Which part of the visual cortex receives information from the macula?

A

Most posterior part = macular cortex

40
Q

Which part of the visual cortex receives information from the peripheral retina?

A

Anterior parts

41
Q

What visual field is affected when there’s a lesion in the right optic nerve?

A

Right eye visual field

42
Q

What visual field is affected when there’s a lesion at the optic chiasm?

A

Temporal hemifields

43
Q

What visual field is affected when there’s a lesion in the right optic tract?

A

Left visual hemifields

44
Q

What visual field is affected when there’s a lesion in the right optic radiation?

A

Upper left quadrant of visual fields of both eyes

45
Q

How can the visual field of the macula be spared when there’s a lesion in the right visual cortex?

A

Only happens with vascular event
Macular cortex supplied by different blood supply than rest of occipital lobe
If infarct in vessel supplying rest of occipital lobe, then macular vision spared

46
Q

What is the tract from the LGN to the primary visual cortex called?

A

Optic radiation

47
Q

What are intrinsically photosensitive ganglion cells?

A

Small population of ganglion cells containing visual pigment = melanopsin
Light activation of melanopsin > intrinsically photosensitive ganglion cells depolarise

48
Q

What are the functions of intrinsically photosensitive ganglion cells?

A 
Circadian rhythm
Sleep regulation
Pupil responses
General info about light levels
Light allodynia
49
Q

What is light allodynia?

A

Photophobia associated with

  • Migraine
  • Ocular injury
  • Infection
50
Q

What do pupil responses depend on?

A

Being able to detect light

Functioning iris

51
Q

What are the two muscles of the iris?

A

Dilator pupillae

Sphincter pupillae

52
Q

Where is one projection of melanopsin ganglion cells?

A

Optical pretectal nucleus (OPN)

53
Q

Where do ganglion fibres heading to the OPN diverge from the visual pathway?

A

After optic chiasm

Before thalamus

54
Q

Where do neurons from the OPN synapse with to control pupil responses?

A

Edinger-Westfal nucleus

55
Q

Which side of the brain does the OPN send fibres to in order to provide information for pupil motor responses?

A

Ipsilateral

Contralateral

56
Q

At what age do babies start to develop circadian rhythms?

A

6-12 weeks

57
Q

Where do intrinsically photosensitive ganglion cells project to in order to provide information for the circadian rhythm?

A

Suprachiasmatic nucleus (SCN) in hypothalamus

58
Q

What is the effect of light in migraines?

A

Worsens pain

59
Q

What is the pain pathway for migraines?

A

Thought to be due to nerves signalling from dura
Pain from dura carried by trigeminal nerve
Dura > trigeminal nerve > brainstem > posterior nucleus of thalamus

60
Q

Why does light cause pain to worsen in migraines?

A

Intrinsically photosensitive ganglion cells synapse in posterior nucleus of thalamus > influence pain fibres

MD1 Neuroscience (55 decks)

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