Lecture 9

Question 1

Extra-ocular muscles & innervation (7) *LR6SO4

Answer 1

Superior rectus - CN III
Inferior rectus - CN III
Medial rectus - CN III
Lateral rectus - CN VI
Superior oblique - CN IV
Inferior oblique - CN III
Levator palpebrae superioris - CN III

Question 2

CN involved in vision

Answer 2

CN III Oculomotor nerve - somatic motor & parasympathetic
CN IV Trochlear nerve - somatic motor
CN VI Abducens nerve - somatic motor
CN II Optic nerve - sensory

Question 3

If you want to look left, which extra-ocular muscles contract

Answer 3

Right eye - MR muscle. Left eye - LR muscle

Question 4

Sphincter pupillae and ciliary muscle

Answer 4

Innervated by CN III
Sphincter pupillae constricts pupils (PSNS)
Ciliary contracts to thicken lens for near vision (PSNS) or relaxes to flatten lens (SNS)

Question 5

What do superior & inferior oblique muscles do?

Answer 5

SO - intorsion (toward nose) eg. for reading
IO - extorsion (away from nose)

Question 6

Effect of lesion to abducens nerve on right side

Answer 6

No innervation to lateral rectus - right eye will look in when looking straight b/c medial rectus is unopposed

Question 7

Visual pathway (3 neuron) from photoreceptor to brain

Answer 7

Photoreceptor activates bipolar cell
Optic nerve (ganglion cells, second order neuron) partially decussates at optic chiasm, becomes tract
Synapses at thalamus LGN
Geniculocalcarine tract (optic radiations) to primary visual cortex

Question 8

Optic nerve vs optic tract (no synapse btwn. nerve & tract)

Answer 8

Optic nerve - from retina to optic chiasm, contains all visual info from each visual field
Optic tract, from optic chiasm to thalamus, contains visual info from the opposite visual field

Question 9

Nasal vs temporal RGC axons

Answer 9

Nasal axons cross optic chiasm, temporal axons stay ipsilateral (because nasal ‘sees’ ipsilaterally, and temporal ‘sees’ contralaterally, nasal must crossover, but temporal can stay)

Question 10

An object from the left VF:

Answer 10

Goes to the nasal half of left retina, and temporal half of right retina

Question 11

Mapping of primary visual cortex

Answer 11

Topographic, reflect in x & y axis between visual field and visual cortex

Question 12

Lesion in the optic nerve causes:

Answer 12

Monocular vision loss

Question 13

Optic chiasm lesion causes:

Answer 13

Bitemporal hemianopia (loss of both temporal visual fields)

Question 14

Lesion in the right optic tract causes:

Answer 14

Homonymous hemianopia (loss of left VF)

Question 15

Dorsal visual pathway (to parietal lobe)

Answer 15

Spatial relationship of objects (middle temporal area)

Question 16

Ventral visual pathway (to temporal lobe)

Answer 16

Object recognition (V4)

Question 17

Damage to the temporal cortex generally results in:

Answer 17

Visual agnosia - poor object recognition (damage to visual pathway)

Question 18

Pupillary light reflex (CN III)

Answer 18

Parasympathetic, direct & consensual
Light shone in 1 eye bilaterally activates pretectal nuclei - stimulates both sides of the Edinger-Westphal Nucleus - Oculomotor nerves synapse on both ciliary ganglions - constricts pupillary muscles (& pupil)

Question 19

Near reflex - involves cortex

Answer 19

Optic tract - LGN - primary visual cortex - visual association cortex - oculomotor nucleus
Constricts ciliary muscles (accomodation)
Convergence of both eyes (via. medial rectus)
Pupillary constriction (Edinger-Westphal nucleus