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Neuro 3 > Lecture 8: Vision Pathways > Flashcards

Lecture 8: Vision Pathways Flashcards

1
Q

What nerves are involved in the Visual System?

A

*CN III - Ocularmotor
*CN II - Optic Nerve
*CN IV - Trochlear
*CN VI - Abducens

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2
Q

What are the six extraocular muscles?

A

*Inferior Rectus
*Superior Rectus
*Medial Rectus
*Lateral Rectus
*Superior Oblique
*Inferior Oblique

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3
Q

What kind of Nerve is the Oculomotor - CN III?

A

It is somatic motor and parasympathetic

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4
Q

What is the Superior Rectus innervated by?

A

CN III - Oculomotor

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5
Q

What is the Inferior Rectus innervated by?

A

CN III - Oculormotor

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6
Q

What is the Lateral Rectus innervated by?

A

CN VI - Abducens

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7
Q

What is the Medial Rectus innervated by?

A

CN III - Oculomotor

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8
Q

What is the Superior Oblique innervated by?

A

CN IV - Abducens

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9
Q

What is the Inferior Oblique innervated by?

A

CN III - Oculomotor

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10
Q

What Oculomotor muscles does CN III - Oculomotor nerve innervate?

A

*Superior Rectus
*Inferior Rectus
*Medial Rectus
*Inferior Oblique

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11
Q

What Oculomotor muscles does CN IV - Trochelar nerve innervate?

A

Superior Oblique

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12
Q

What Oculomotor muscles does CN VI - Abducens nerve innervate?

A

Lateral Rectus

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13
Q

What is the acronym to remember the innervation of the lateral muscles?

A

LR6SO4 (Lateral Rectus by CN VI - Abducens, Superior Oblique by CN IV - Trochlear

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14
Q

Other than the Extraocular muscles what does the CN III - Oculomotor Nerve innervate?

A

The levator palpebrae muscle

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15
Q

What innervates the Levator Palpebrae Superioris?

A

CN III - Oculomotor

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16
Q

What does the Levator Palpebrae Superioris allow for?

A

Opening of the eyes

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17
Q

What structures does the oculomotor nerve emerge between?

A

The midbrain and the pons

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18
Q

Through what does the Oculomotor nerve exit?

A

The Superior Orbital Fissure

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19
Q

Where does the Trochlear nerve originate?

A

The back of the brainstem

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20
Q

Where does the Trochlear Nerve IV exit the skull?

A

The superior orbital fissure

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21
Q

What nerves exit the Superior Orbital Fissure?

A

*Oculomotor Nerve
*Trochlear Nerve
*Abducens Nerve

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22
Q

What does the Trochlear Nerve innervate?

A

The Superior Oblique

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23
Q

What does the Abducens nerve innervate?

A

The Lateral Rectus

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24
Q

What does the Lateral Rectus do?

A

Moves the eye laterally

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25
Q

What does the Medial Rectus do?

A

Moves the eye medially

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26
Q

What does the Superior Rectus do?

A

Moves the eye up and out

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27
Q

What does the Inferior rectus do?

A

Moves the eye down and out

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28
Q

What does the Superior Oblique do?

A

Moves the eye down and in (depresses and intorts)

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29
Q

What does the Inferior Oblique?

A

Moves the eye up and in

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30
Q

What do Retinal Ganglion cells do?

A

Transduce visual information to the brain

31
Q

What does the Cornea?

A

Helps to focus incoming light

32
Q

What sits under the cornea?

A

Aqueous humour

33
Q

What does aqueous humor do?

A

Maintain pressure inside the eye

34
Q

What does the Iris do?

A

Controls light input

35
Q

What muscles sit on the Lens?

A

Ciliary Muscles

36
Q

What does the lens do?

A

Focuses the light

37
Q

What does the Vitreous Humour do?

A

Maintains pressure in the eye and focus light on the retina

38
Q

What is the Macula of the eye?

A

Where the highest concentration of photoreceptors is

39
Q

What is the Choroid?

A

The part of the eye that supplies oxygen and nutrients to the outer retina

40
Q

What is the white part of the eye?

A

The Sclera

41
Q

What is the Sclera homologous to?

A

The Dura mater of the brain

42
Q

Developmentally where does the eyeball come from?

A

The Diencephalon

43
Q

What nerves in the eye send their axons to the optic tract?

A

The Retinal Ganglion cells

44
Q

What is the distinction between Optic Nerve and Optic Tract?

A

From the eye to the optic chiasm it is known as the optic nerve. From the optic chiasm and beyond it is known as tract

45
Q

What is the distinction between Optic Nerve and Optic Tract?

A

From the eye to the optic chiasm it is known as the optic nerve. From the optic chiasm and beyond it is known as tract

46
Q

What does the CN II - Optic Nerve exit the skull from?

A

The Optic Canal

47
Q

What exits the Optic Canal?

A

CN II - Optic nerve

48
Q

What is the Visual Pathway?

A
  1. Retinal Ganglion cells
  2. Optic nerve
  3. Optic chiasm
  4. LGN of the thalamus
  5. Primary Visual Cortex
49
Q

What are the rules with the visual field?

A

*Temporal Visual field axons stay ipsilateral
*Nasal Visual Field axons cross the optic chiasm

50
Q

How is the primary visual cortex mapped?

A

The fovea and the surrounding areas take up more space in the primary visual cortex

51
Q

What does a lesion to the optic nerve do?

A

Cause you to be unable to see an entire visual field either left or right

52
Q

What can cause you be unable to see and entire visual field?

A

A lesion to the optic nerve

53
Q

What is it called when you are unbale to see an entire visual field?

A

Anopsia

54
Q

What is Anopsia?

A

Being unable to see an entire visual field

55
Q

What does a lesion to the optic chiasm do?

A

Causes tunnel vision (Bitemporal hemianopsia)

56
Q

What causes tunnel vision?

A

A lesion to the optic nerve

57
Q

What is Bitemporal Hemianopsia?

A

Tunnel vision

58
Q

What does a lesion to the optic tract cause?

A

The inability to see in the right nasal and left temporal field or the left nasal field and the right temporal field

59
Q

What is the name for what a lesion in the optic tract causes?

A

Left homonymous hemianopsia

60
Q

What does the Dorsal Pathway recognize?

A

Spatial relationships of objects (speed and direction of movements)

61
Q

What does the Ventral Pathway recognize?

A

Object recognition (neurons relate to shape, color, texture)

62
Q

Where does the Dorsal Pathway go?

A

To the parietal lobe

63
Q

Where does the ventral Pathway go?

A

To the temporal lobe

64
Q

What does the damage to the temporal cortex do?

A

Poor object recognition (visual agnosia)

65
Q

What are the two parasympathetic roles of the CN III (oculomotor)?

A

*Pupillary light reflex
*Near (accommodation) reflex

66
Q

How many neurons are in the parasympathetic oculomotor nerve pathways?

A

Two neurons

67
Q

What is the general pathway of the parasympathetic pathways of the oculomotor nerve?

A
  1. Neurons emerge from the brainstem
  2. Find the postganglionic sympathetic neuron in the sympathetic ganglion
  3. The postganglionic neuron then goes to the sphincter or ciliary muscles
68
Q

What is the Pupillary Light Reflex?

A

When both pupils constrict in response to light

69
Q

What are the steps in the Pupillary light reflex?

A
  1. Light is shined in one eye
  2. This information is sent from the optic nerve
  3. It acts on the pretectal nuclei in the midbrain
  4. They then activate the Edinger-Westphal nucleus
  5. This sends projects to the preganglionic neuron. This neuron synapses in the ciliary ganglion to the postganglionic neuron
  6. It then tells the muscles of the sphincter to constrict (two neurons)
70
Q

Where does visual information synapse in the thalamus?

A

The Lateral Geniculate Nucleus (LGN)

71
Q

What will happen if there is a lesion in the optic nerve to the Pupillary light reflex?

A

If the lesion is on the same side as the light the reflex will not occur because there is no information going to the brain. If there is light shown on the other eye both eye will constrict

72
Q

What is the near reflex?

A

The constriction of the pupils and change in flattening of the lens to get the right amount of light to the retina. And the convergence of the two eyes

73
Q

What are the steps in the near reflex?

A
  1. Visual information goes from both eyes goes to the optic nerve
  2. Goes the LGN of the thalamus
  3. Then to the primary visual cortex
  4. Then to the association cortex
  5. It acts on the oculomotor nucleus (LMN)
  6. It goes to the Medial rectus muscle causing the eyes to contract and turn in
  7. Parasympathetic also go to the ciliary ganglion act on the pupil constriction and ciliary muscles to cause it to contract and flatten

Neuro 3 (21 decks)

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