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Yr2 Control - Term 2 and 3 > Visual Pathway > Flashcards

Visual Pathway Flashcards

1
Q

Which part of the eye contains no photoreceptors?

A

The optic disc.

-blind spot on retina

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2
Q

Where is the optic disc located?

A

On the retina, medial to the fovea.

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3
Q

What is the retina?

A

The nerve layer that lines the back of the eye, senses light, and creates impulses that travel through the optic nerve.

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4
Q

What are the 2 layers of the retina?

A
  • Non-neuronal layer

- Neuronal layer

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5
Q

What does the non-neuronal layer of the retina consist of?

A

Pigmented epithelium.

-sits against the choroid of the eyeball and absorbs photons

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6
Q

What are photons?

A

Particles of light energy.

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7
Q

What is the function of the pigmented epithelium?

A

Surrounds photoreceptors via melanin-filled microvilli.

-maintains their metabolic activity

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8
Q

What does the neuronal layer of the retina contain? (4)

A
  • Photoreceptors
  • Bipolar neurons
  • Ganglionic cells
  • Interneurons
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9
Q

What do photoreceptors do?

A

Receive photons and convert them into signals.

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10
Q

What are the 2 types of photoreceptors?

A
  • Cone cells

- Rod cells

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11
Q

Why does light have to pass through other fibres to get to photoreceptors?

A

Decreases the intensity of light reaching the retina.

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12
Q

What do bipolar neurons do?

A

Connect photoreceptors to ganglionic cells.

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13
Q

What do ganglionic cells combine to form as they leave the retina?

A

The optic (II) nerve.

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14
Q

What is the function of interneurons?

A

Interconnect photoreceptors/bipolar neurons/ganglionic cells.
-modulate transmission and sharpen information to the cortex

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15
Q

What are the 2 types of interneuron?

A
  • Horizontal

- Amacrine

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16
Q

Where are horizontal interneurons located?

A

At the level of photoreceptors and bipolar neurons.

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17
Q

Where are amacrine interneurons located?

A

At the level of bipolar neurons and ganglionic cells.

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18
Q

What process occurs in the neuronal layer of the retina?

A

Photochemical reactions tranduce photons (light energy) to electrical energy.

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19
Q

How many neurons are there from the retina to the cortex?

A

Three.

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20
Q

What is the pathway of light energy from the retina to the cortex?

A 
Photoreceptors
>> 1* BIPOLAR CELLS
>> 2* GANGLIONIC CELLS
>>Optic nerve
>> Lateral geniculate nucleus (thalamus)
>> 3* OPTIC RADIATION
>> 1* visual cortex (cerebral cortex)
>> Association centre
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21
Q

What is the optic nerve an outgrowth of?

A

The diencephlon.

-part of the CNS

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22
Q

What membranes surround the eyeballs?

A

Meninges.

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23
Q

What effect can increased CSF/ICP have on vision?

A

Can cause the optic nerve to swell and compress the retinal central vein&raquo_space; PAPILLOEDEMA.
-lifts retina away from the pigmented epithelium

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24
Q

What is papilloedema?

A

Optic disc swelling due to increased ICP.

|&raquo_space; headache, drowsiness, blurred vision

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25
Q

Which part of the thalamus does the visual pathway go to?

A

Lateral geniculate nucleus.

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26
Q

NB. Which part of the thalamus does the auditory pathway go to?

A

Medial geniculate nucleus.

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27
Q

Where does vision from the same area of the visual field travel?

A

Enters different eyes, but travels down the same optic tracts.

28
Q

Where does the medial (nasal) retina send information to?

A

The contralateral thalamus.

29
Q

Where does the lateral (temporal) retina send information to?

A

The ipsilateral thalamus.

30
Q

Where does information from the medial retina cross over?

A

At the optic chiasma&raquo_space; contralateral lateral geniculate nuclei.

31
Q

On the medial surface of the brain, what lies either side of the calcarine sulcus?

A

Striate cortex (somatosensory).

32
Q

What lies adjacent to the striate cortex?

A

The visual association cortex.

33
Q

What is the function of the visual association cortex?

A

Receives information from the 1* visual cortex and processes it with memories&raquo_space; understanding.

34
Q

Where does information from the left half of the visual field travel to?

A

Right hemisphere.

35
Q

Where does information from the right half of the visual field travel to?

A

Left hemisphere.

36
Q

Where does information from the upper visual field travel to?

A

The lower bank of the calcarine sulcus.

37
Q

Where does information from the lower visual field travel to?

A

The upper bank of the calcarine sulcus.

38
Q

Where does information from the centre of the visual axis (macula) travel to?

A

Occipital pole.

-posterior occipital lobe

39
Q

What is scotoma?

A

Localised patch of blindness.

40
Q

What is anopia?

A

Loss of 1+ quadrants of the visual field.

41
Q

What is hemianopia?

A

Loss of half of the visual field.

42
Q

What does homonymous mean?

A

Visual losses are similar on both sides.

43
Q

What does heminymous mean?

A

Visual losses are different on both sides

44
Q

Damage to which part of the visual pathway leads to monocular damage?

A

Optic nerve.

45
Q

Damage to which part of the visual pathway leads to heteronymous hemianopia?

A

Optic chiasma.

46
Q

Damage to which part of the visual pathway leads to homonymous hemianopia?

A

Optic tract.

47
Q

Damage to which part of the visual pathway leads to homonymous hemianopia with macular sparing?

A

Optic radiation.

48
Q

How is scotoma often caused?

A

Banging the back of the head.

-1* visual cortex damage

49
Q

Do all optic tract fibres go to the lateral geniculate nuclei?

A

No.

50
Q

Where do 10% of optic tract fibres go?

A

Pre-tectal area (midbrain).

51
Q

What does the pupillary light reflex test?

A

The ability of the pupill to respond to light.

52
Q

What 2 cranial nerves are involved in the pupillary light reflex?

A
  • Optic (II) nerve - sensory

- Occulomotor (III) nerve - motor

53
Q

Which muscle is tested by the pupillary light reflex?

A

Iris sphincter muscle.

54
Q

What is the iris sphincter muscle controlled by?

A

Parasympathetic innervation from the occulomotor (III) nerve, via the Edinger-Westphal nucleus.

55
Q

What are the 2 components of the pupillary light reflex?

A
  • Direct

- Consensual

56
Q

What is the direct component of the pupillary light reflex?

A

Light in one eye causes the same pupil to constrict.

57
Q

What is the consensual component of the pupillary light reflex?

A

Light in one eye causes the other pupil to constrict.

58
Q

What does the Edinger-Westphal nucleus contain?

A

Preganglionic PS motor neurons from both sides of the visual field that leave the brain with the occulomotor nerve.

59
Q

What happens in the pupillary light reflex if the patient has optic nerve damage (sensory)?

A

Other pupil would still react if light is shone into 1 eye.

60
Q

What happens in the pupillary light reflex if the patient has occulomotor nerve damage (motor)?

A

No way to constrict the muscle.

-pupil slightly dilated

61
Q

What is the accommodation reflex?

A

Changes that occur in the eye when gaze is transferred from a distant object to a near object.

62
Q

What are the 3 changes that occur in the accomodation reflex?

A
  • Accommodation
  • Pupil constricts
  • Ocular convergence
63
Q

What is accommodation?

A

Ciliary muscles contract&raquo_space; lens becomes more rounded.

-image focused on retina

64
Q

What causes the pupil to constrict in the accommodation reflex?

A

Sphincter pupillae muscle.

65
Q

What causes ocular convergence?

A

Medial rectus muscle.

-image focused on the fovea

66
Q

Where do afferent fibres from the eye travel?

A

In the optic nerve
» cortex
» occulomotor nerve

67
Q

Where do efferent fibres to the eye travel?

A

Within the occulomotor nerve.

Yr2 Control - Term 2 and 3 (17 decks)

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