21.6: NS, Visual pathway Flashcards Preview

Week 21: Neuroscience > 21.6: NS, Visual pathway > Flashcards

Flashcards in 21.6: NS, Visual pathway Deck (21)
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1
Q

Bitemporal hemianopia?

A

(II ) ( II)

2
Q

In response to light, what these ganglion cells do?
ON
OFF

A

ON: depolarise
OFF: hyperpolarise

3
Q

What are the two types of ganglion cells?

A

M (parasol): motion

P (midget): colour, acuity

4
Q

Which ganglion cell is most numerous?

A

P: 85%

5
Q

What is the target/termination of most GCs?

What is its role?

A

Lateral geniculate nucleus (thalamus)

A relay station for vision

6
Q

Fibres from ___ nerves combine to form the _____ ____.

A

Fibres from optic nerves combine to form the optic chiasm

7
Q

Where is the optic chiasm?

A

Base of the brain, anterior to the pituitary

8
Q

Which part of the visual field does the R cortex encode?

A

L visual field (both eyes)

9
Q

What will a pituitary tumour impinge on? What does this lead to?

A

Optic chiasm, visual field defect (bitemporal hemianopia)

10
Q

What are the layers of the LGN?

Which are for M/P?

Which are for L/R?

A

6 layers

1, 2: Magnocellular layers

3-6: Parvocellular layers

R eye: 2,3,5
L eye: 1,4,6

11
Q

What is an optic radiation?

A

Giant white matter tract (neurons from LGN)

12
Q

Where is central and peripheral vision encoded?

A

Central: posterior occipital lobe
Peripheral: calcarine fissure

13
Q

If a lesion is anterior to the chiasm, what happens to vision?

A

Unilateral vision (one eye defect)

14
Q

If both eyes are affected, where is the lesion?

If the same side on both eyes is affected where is the lesion?

A

Chiasm and back

After the chiasm

15
Q

What have we learned about the neural activity of ganglion cells from blind subjects?

A

Even without photoreceptors, the ganglion cells respond.

16
Q

What is the pain pathway for a migraine?

A

Dura (meninges blood vessels)–> V–>brainstem–>thalamus (posterior nucleus)

17
Q

What are ipGCs? What do they contain? What do they do to light?

A

Intrinsically photosensitive GCs. Contain melanopsin (depolarise to light)

18
Q

What controls pupil:
dilation
constriction

A

Dilation: dilator pupillae (SNS)

Constriction: sphincter pupillae muscle (PSNS, CNIII)

19
Q

What is the pathway for pupil responses?

A

Light–>ipGC–>optical pretectal nucleus (midbrain)–>EW nucleus–>CNIII to opposite eye (constriction)

20
Q

What drives circadian rhythm? How?

A

SCN (suprachiasmatic nucleus) in the hypothalamus (ipGCs project here)

21
Q

What happens with regards to photophobia from a migrane in blind patients (with some and without light perception)

A

No light perception: NO aura or effect of light

Some light perception: Aura, light exacerbates migrane