4.1 Visual Pathways Flashcards Preview

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Flashcards in 4.1 Visual Pathways Deck (59):
1

What do cone cells detect?

Colour and HD

C for colour

2

What is the fovea?

Dip below the optic disc

3

What is contained within the fovea?

Highest concentration of cone cells

4

What is the choroid?

Part of the vascular supply

5

What does retinal pigment epithelium contain?

Melanin

6

What does the retinal pigment epithelium do?

Makes sure you dont have excessive refraction, absorbs some light instead

7

Why are albinos sensitive to normal levels of light?

Because they lack melanin in their retinal pigment epithelium

8

Where is the blind spot in the back of the eye and why is it there?

At the optic disc

Because there are no photoreceptor cells

9

What do horizontal cells do?

Responsible for lateral inhibition

Inhibit bipolar cells activated outside the central field of view

10

How does light travel once it hits the neural layer of the eye?

Travels through to the photoreceptor cells all the way at the back (bar choroid)

Makes its way back through bipolar cells to the axons of ganglion cells to the optic nerve

11

What runs alongside the optic nerve as it leaves the eye?

Central artery and vein of the retina

12

What is the retina?

Light sensitive tissue that lines the back of the eye

13

Why might an optic disc be swollen?

Due to an increased ICP

14

What do patients see when their central retinal artery becomes occluded?

Amaurosis fugax

15

What is amaurosis fugax?

Temporary loss of vision

Like a black curtain coming down

16

How are fibres medial to the retina referred to?

Nasal

17

How are fibres lateral to the retina referred to?

Temporal

18

Which retinal fibres in the eye decussate?

Medial (Nasal)

19

Do Temporal retinal fibres of the eye decussate, or not?

Stay ipsilateral

20

Where do the nasal retinal fibres decussate?

At the optic chiasm

21

What kind of retinal fibres does the optic nerve contain?

Contains all the retinal fibres from the SAME (IPSILATERAL) eye

22

What does the optic tract contain?

ISPILATERAL temporal retinal fibres

CONTRALATEREAL nasal retinal fibres

23

Where do the optic tracts run to?

Lateral geniculate nucleus

24

Where is the lateral geniculate nucleus located?

Thalamus

25

What is the basic function of the lateral geniculate nucleus?

Relay point for the visual fibres to get to the back of the cortex

26

What structures travel from the lateral geniculate nucleus (thalamus) to the primary visual cortex?

Optic radiations

27

What are the two different types of optic radiations?

Superior

Inferior

28

Which fibres continue as superior optic radiations once they leave the lateral geniculate nucleus?

Superior nasal and temporal fibres

29

Where do the superior optic radiations run?

In the parietal lobe

30

Where do the inferior optic radiations run?

In the temporal lobe

31

Where do both the superior and inferior radiations end up?

Primary Visual Cortex in the Occipital lobe

32

How does light hit the retina, if it comes from the medial side?

Hits the lateral (temporal) side

33

Which retinal fibres are responsible for the nasal visual fields and vice versa?

Temporal fibres for nasal visual fields

Nasal fibre for the temporal visual fields

34

Which retinal fibres are responsible for the superior visual fields and vice versa?

Inferior retinal fibres for superior fields

Superior retinal fibres for inferior fields

35

Is a visual field defect referring to the area of visual loss or the site of the lesion?

area of visual loss

36

How do lesions to the fibres BEFORE the optic chiasm affect the visual fields?

Unilateral

Ipsilateral

37

How do lesions to the fibres AT the optic chiasm affect the visual fields?

Bilateral

38

How do lesions to the fibres AFTER the optic chiasm affect the visual fields?

Bilateral

Contralateral

39

What kind of visual defect would be cased by an optic nerve lesion?

Monocular blindness

The entire visual field of one eye is lost

40

What might cause monocular blindness in children?

Retinoblastoma

41

What kind of visual defect would be caused by a lesion at the optic chiasm?

Explain

Bitemporal hemianopia

BOTH nasal fibres affected

Temporal fields lost

42

What kind of visual defect would be caused by a lesion at the optic tract?

Which visual field would be affected (relative to the side of the lesion)?

Homonomous hemianopia

The contralateral side

43

What the most common cause of a homonymous hemianopia?

Vascular (stroke)

(Also neoplasia and trauma)

44

What are the superior optic radiations responsible for?

Inferior fields of vision

45

What are the inferior optic radiations responsible for?

Superior fields of vision

46

If the superior optic radiations had a lesion, what would the visual field defect be?

Contralateral LOWER quadratic anopia

47

What is the blood supply to the occipital lobe like?

Dual blood supply

Posterior cerebral artery

Middle cerebral artery

48

Why does macular sparing occurring?

Stroke affecting PCA - most of occipital lobe lost

MCA supplies central part of occipital lobe

Central part of occipital lobe represents macula

Macula vision spared

49

The afferents of which cranial nerve are stimulated by light?

CN II

50

What is the course of the CN II afferents in the light reflex?

DOES NOT GO TO LGN

Synapses in pretectal area

51

What do the afferents of CN II synapse to in the light reflex?

Neurones supplying Edinger Westphal nucleus BILATERALLY

52

What happens after neurones synapse in the Edinger-Westphal nucleus in the light reflex?

BOTH CN IIIs are stimulated

Direct AND consensual pupillary constriction

53

Which fibres are are stimulated in the Occulomotor nerve in the light reflex?

Parasympathetics

54

What is the accommodation reflex required for?

Near vision

Focus on a near object

55

What are the three aspects of the accommodation reflex?

Convergence

Pupillary constriction

Convexity

3 Cs

56

What enables convergence in the accommodation reflex?

Medial rectus muscles

57

What enables pupillary constriction in the accommodation reflex? Why is it needed?

Constrictor pupillae

Focus light better

58

What enables the convexity of the lens in the accommodation reflex? Why is it needed?

Ciliary muscle

Increase refractive power

59

What is the course of the accommodation reflex?

Optic nerve --> LGN

LGN --> Visual cortex

Visual cortex --> Pretectal area

Pretectal area --> EWN

Occulomotor nerve