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Brain and behaviour > Visual pathways > Flashcards

Visual pathways Flashcards

1
Q

Where does the optic nerve travel to from the eye?

A

The optic chiasm

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2
Q

Where do axons pass into once they move through the optic chiasm?

A

The optic tract

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3
Q

Briefly describe where the optic chiasm is positioned in the brain

A

Immediately above the pituitary

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4
Q

What cells supply the axons that make up the optic nerve?

A

Retinal ganglion cells

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5
Q

Where do majority of retinal ganglion cells project?

A

Lateral geniculate nuleus (visual thalamic relay)

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6
Q

Where do lateral geniculate nucleus cells send axons?

A

Primary visual cortex (area 17) in the occipital lobe

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7
Q

What would happen if the lateral geniculate- occipital pathway is damaged?

A

The person will be blind

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8
Q

What structure is tested when a patient is asked to follow your finger with their eyes?

A

Superior colliculus

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9
Q

Where is the superior colliculus located?

A

Midbrain

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10
Q

What does the superior colliculus connect to, and what is the function of this?

A

The medial longitudinal fasciculus

Links together and synchronises nuclei

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11
Q

What is the optic tectum?

A

Another name for superior colliculus

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12
Q

What nucleus controls pupillary light reflex?

A

Edinger Westphal nucleus

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13
Q

Describe the pathway of axons from cells of LGN to visual cortex

A

via the optic radiation

project back anteriorly in Meyer’s loop and then run alongside the posterior horn of lateral ventricle to occipital lobe

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14
Q

Define left visual field

A

Everything to the left of your fixation point in both eyes

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15
Q

What part of the brain ‘sees’ the left visual field

A

right visual cortex

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16
Q

Why does left visual field project to right visual cortex and vice versa?

A

Nasal hemiretina from left eye projects to right visual cortex, as does the temporal hemiretina from right eye.

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17
Q

Define scotoma

A

A patch of blindness

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18
Q

What is the result of partial optic nerve legion?

A

Ipsilateral scotoma

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19
Q

What is the result of complete optic nerve lesion?

A

Complete blindness in that eye

20
Q

What is the result of optic chiasm lesion

A

Bitemporal hemioanopia

21
Q

What is the result of an optic tract lesion

A

Homonymous hemiapopia

22
Q

What is the result of damage of the Meyer’s loop?

A

Homonymous upper quadrant anopia

23
Q

What is the result of optic radiation lesion?

A

Homonymous hemianopia

24
Q

What is the result of visual cortex lesion

A

Homonymous hemianopia

25
Q

Name the four key visual reflexes

A

Pupillary eye reflexes
Accomodation reflex
Vestibulo-ocular reflex
Blink reflex

26
Q

How are cranial nerves III, IV and VI linked?

A

fibre tract called the medial longitudinal fasciculus

27
Q

Which cranial nerves are involved in pupillary light reflex

A

In on II, out on III

28
Q

Describe the passage of axons in the pupillary light reflex

A

Axons of CN II go the pretectal nucleus is the superior colliculus. From here, go to Edinger-Westphal nucleus and out on CN III to ciliary ganglion.
This sends axons to pupillary constrictor muscle
Constrictor of this reduces pupil size

29
Q

What can block the pupillary light reflex?

A

Atropine

30
Q

What are the 3 components of the accomodation reflex?

A

Pupillary constriction
Thickening of lens
Convergence

31
Q

What is the input for pupillary constriction as part of accomodation reflex?

A

Comes from descending projections from frontal eye fields in premotor cortex

32
Q

What is function of pupillary constriction in accommodation reflex?

A

Focusing on close objects/ depth of field

33
Q

Can accomodation reflex occur in unconcious person?

A

No

34
Q

What part of the brain controls the accommodation reflex?

A

Frontal eye fields (specialised part of premotor area)

35
Q

What is the result of damage to FEFs

A

Inability to direct gaze from one object to another

36
Q

Describe the shape of the lens at rest

A

Under tension from ring of suspensory ligaments which flatten it away from relaxed shape

37
Q

Describe the shape of the lens when the ciliary muscle contracts

A

Reduces diameter of ring of suspensory ligaments, slackens the tension and lens bulges out into relaxed shape

38
Q

How is the lens thickened during accomodation and why?

A

Tension in suspensory ligaments is reduced and lens thickens to normal shape to focus on obkects

39
Q

Which muscles cause convergence as part of accommodation reflex

A

Medial rectus muscles

40
Q

What is the vestibulo-ocular reflex?

A

If you turn your head to the side whilst looking at distant object, eyes rotate in opposite direction of the head to keep direction of gaze constant and object stays in view

41
Q

What is the input and output of the vestibulo-ocular reflex?

A

In: CN VIII, receiving signals from semicircular canals
Out: CN VI and CN III

42
Q

How is the vestibulo-ocular reflex tested clinically?

A

Holding someones eyes open and gently rotating the head from side to side
Eyes should rotate in the head to keep direction constant

43
Q

WHat is nystagmus?

A

Form of VOR caused by continuing rotation of fluid in the semicircular canals

44
Q

Function of blink reflex

A

Projects eye from foreign bodies

45
Q

Input and output of blink reflex?

A

V1 branch of trigeminal nerve

Out- facial nerve input to obicularis oculi muscles

Brain and behaviour (22 decks)

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