Visual Pathway Flashcards Preview

MD1 Neuroscience > Visual Pathway > Flashcards

Flashcards in Visual Pathway Deck (60):
1

What kind of glutamate receptors can bipolar cells express?

Metabotropic
Ionotropic

2

Why are there different types of ganglion cells?

Each type provides info for different stream of vision

3

What are two types of ganglion cells?

M/parasol
P/midget

4

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

Each type has ON and OFF type
- M ON
- M OFF
- P ON
- P OFF

5

Describe M ganglion cells

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

6

Describe P ganglion cells

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

7

What are the targets of ganglion cell axons?

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

8

Why do ganglion cell axons project to the LGN?

Major target of most ganglion cells
Visual pathway

9

Why do ganglion cell axons project to the pretectum?

Pupil responses

10

Why do ganglion cell axons project to the suprachiasmatic nucleus?

Circadian rhythm

11

Why do ganglion cell axons project to the superior colliculus?

Eye movements

12

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

Photophobia

13

What is the optic chiasm?

Fibres from right and left optic nerves combine

14

How many ganglion fibres cross at the optic chiasm?

Half

15

Where is the optic chiasm?

Base of brain anterior to pituitary

16

From which hemifield does the nasal retina receive light information?

Temporal hemifield

17

From which hemifield does the temporal retina receive light information?

Nasal hemifield

18

Which fibres cross at the optic chiasm?

Nasal fibres

19

Which hemisphere views each hemifield?

Right visual hemifield viewed by left hemisphere
Left visual hemifield viewed by right hemisphere

20

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

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

21

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

Optic tract

22

Where do ganglion cell axons in the optic tract synapse?

LGN

23

How many neurons are there in the visual pathway?

2

24

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

Pituitary gland just below
Condition affecting it can affect chiasm; eg: in pituitary macroadenoma

25

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

Bitemporal hemianopia

26

Which hemifields are affected in bitemporal hemianopia?

Temporal hemifields

27

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

LGN

28

How is information in the LGN segregated?

By eye and ganglion cell type

29

How many layers are there in the LGN?

6

30

What are the types of cells in the LGN?

Magnocellular
Parvocellular

31

Where do M ganglion cells synapse?

Magnocellular layers: 1 and 2

32

Where do P ganglion cells synapse?

Parvocellular layers: 3-6

33

Which layers receive input from the right eye?

2, 3, 5

34

Which layers receive input from the left eye?

1, 4, 6

35

Where do LGN neurons project to?

Primary visual cortex (V1)

36

What is the Broddman's area of V1?

Area 17

37

Where in the brain is the primary visual cortex?

Occipital lobe around calcarine fissure
- On medial aspect
- Upper and lower banks around fissure

38

How is information organised in the primary visual cortex?

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

39

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

Most posterior part = macular cortex

40

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

Anterior parts

41

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

Right eye visual field

42

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

Temporal hemifields

43

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

Left visual hemifields

44

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

Upper left quadrant of visual fields of both eyes

45

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

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

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

Optic radiation

47

What are intrinsically photosensitive ganglion cells?

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

48

What are the functions of intrinsically photosensitive ganglion cells?

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

49

What is light allodynia?

Photophobia associated with
- Migraine
- Ocular injury
- Infection

50

What do pupil responses depend on?

Being able to detect light
Functioning iris

51

What are the two muscles of the iris?

Dilator pupillae
Sphincter pupillae

52

Where is one projection of melanopsin ganglion cells?

Optical pretectal nucleus (OPN)

53

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

After optic chiasm
Before thalamus

54

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

Edinger-Westfal nucleus

55

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

Ipsilateral
Contralateral

56

At what age do babies start to develop circadian rhythms?

6-12 weeks

57

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

Suprachiasmatic nucleus (SCN) in hypothalamus

58

What is the effect of light in migraines?

Worsens pain

59

What is the pain pathway for migraines?

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

Why does light cause pain to worsen in migraines?

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

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