Lec 9 Vision

Question 1

At the chiasm, what % cross? What % continue ipsilaterally?

Answer 1

60% cross.
40% ipsi.

Question 2

Why do only some cross at the chiasm?

Answer 2

important for binocular vision & depth perception

Question 3

Optic Tracts project where? (4)

Answer 3

Lateral Geniculate (thalamus)
Suprachiasmatic Nucleus (hypothal)
Pretectum
Superior Colliculus (midbrain)

Question 4

Lateral Geniculate projects where?

Answer 4

optic radiations, then to primary visual cortex (V1)

Question 5

primary visual cortex = brodmans area ___

Answer 5

17

Question 6

Ventral pathway of primary visual cortex projects where?

Answer 6

temporal lobe

Question 7

Dorsal pathway of primary visual cortex projects where?

Answer 7

parietal lobe

Question 8

Retino-hypothalamic path functions

Answer 8

circadian rhythm
ANS response

Question 9

Pretectum function

Answer 9

pupillary reflex

Question 10

Pretectum projects where?

Answer 10

Edinger-Westphall (midbrain)

Question 11

Edinger-Westphall PRE-ganglionic projects where?

Answer 11

CN 3 -> ciliary ganglion (lens accom)

Question 12

Edinger-Westphall POST-ganglionic projects where?

Answer 12

sphincter pupillary muscle

Question 13

Superior colliculus function

Answer 13

coordinate head/eye movements

Question 14

Pupillary direct response

Answer 14

stimulated eye constricts

Question 15

Pupillary consensual response

Answer 15

contralateral (un-stimulated) eye also contracts

Question 16

Axons from the Nasal retina ____ in the chiasm (cross/stay on same side)?

Answer 16

cross

Question 17

Axons from the Temporal retina ____ in the chiasm (cross/stay on same side)?

Answer 17

stay on same side

Question 18

Left visual field: which nasal retina, which temporal retina, which optic tract?

Answer 18

• *Left** nasal retina
• *Right** temporal retina
• *Right** optic tract

Question 19

Right visual field: which nasal retina, which temporal retina, which optic tract?

Answer 19

• *Right** nasal retina
• *Left** temporal retina
• *Left** optic tract

Question 20

Meyers loop: where is it, what part of visual field does it view?

Answer 20

inferior Lateral Geniculate.
superior visual field.

Question 21

Superior Lateral Geniculate views what part of the visual field?

Answer 21

inferior

Question 22

Anopsia vs. Scotoma

Answer 22

Anopsia = large deficit
Scotoma = small deficit

Question 23

Damage at A

Answer 23

complete loss of R visual field

Question 24

Damage at B (Chiasm)

Answer 24

Bitemporal Hemianopsia
loss of fibers crossing (from both nasal retina) = loss of both temporal fields.

Question 25

Damage at C (Optic Tract)

Answer 25

Left Homonymous Hemianopsia. loss of fibers from **R temporal** & **L nasal** = loss of **R nasal** field + loss of **L temporal** field

Question 26

Damage at D (Optic Radiations)

Answer 26

Superior Homonymous Quadrantopsia. loss of fibers from **R superior temporal** & **L superior nasal** = loss of **L temporal** + **R nasal** superior fields

Question 27

Damage at E (Primary Visual Cortex)

Answer 27

Homonymous Hemianopsia w/ Macular Sparing unknown mechanism

Question 28

Role of extraocular musc

Answer 28

Foveation: direct fovea towards object of interest

Question 29

Lat/Med Rectus actions

Answer 29

horizontal movements (ABD/ADD)

Question 30

Sup/Inf Rectus actions

Answer 30

vertical movements (elev/depress)

Question 31

Sup/Inf Oblique actions

Answer 31

Intorsion: top of eye toward nose. Extorsion: top of eye away from nose.

Question 32

Elevation force couple

Answer 32

Sup Rectus Inf Oblique

Question 33

Depression force couple

Answer 33

Inf Rectus Sup Oblique

Question 34

Vestibulo-Ocular Reflex (VOR)

Answer 34

when head moves, eyes move the same distance/speed in _OPPOSITE_ direction

Question 35

Why are saccadic movements considered "ballistic"

Answer 35

cannot respond to changes in target position once already started. If a target moves during a saccade, a second saccade must be generated.

Question 36

Amplitude of saccades

Answer 36

duration of neuron activity (freq of APs)

Question 37

Direction of saccade is governed by

Answer 37

_2 gaze centers in Reticular Formation_ 1. PPRF 2. Rostral Interstitial Nucleus

Question 38

PPRF = ____ (horizontal/vertical) movements

Answer 38

horizontal

Question 39

Rostral Interstitial Nucleus = ____ (horizontal/vertical) movements

Answer 39

vertical

Question 40

What happens once PPRF is activated?

Answer 40

Activates **ipsi** Abducens, which activates LMNs (to **ipsi** Lat Rectus) and Internuclear neurons (to **contra** Oculomotor = Med Rectus)

Question 41

L PPRF is activated by

Answer 41

R frontal eye field R superior colliculus