Visual System

Question 1

where does the majority of refraction / bending of light occur in the eye?

Answer 1

the cornea

Question 2

vitreous body function

Answer 2

a gel (high in hyaluronic acid) that gives shape to the eye

Question 3

the retina comes from where?

Answer 3

the retina is an outgrowth of the brain from the diencephalon

Question 4

what is the only cell type that sends axons out of the eye?

Answer 4

retinal ganglion cells

Question 5

where are the retinal ganglion cells located?

Answer 5

in the inner surface of the retina

Question 6

where is light converted into chemical energy?

Answer 6

in the rods and cones

Question 7

are the axons myelinated in the eye?

Answer 7

axons are NOT myelinated in the eye b/c myelin can scatter light

Question 8

describe the area surrounding the fovea

Answer 8

there is a physical removal of all things surrounding the fovea. Ie no vasculature

Question 9

cones function

Answer 9

high acuity vision

color

Question 10

rods function

Answer 10

peripheral vision

black and white and night vision

Question 11

optic disc

Answer 11

“blind spot” this is where the blood vessels enter and exit as well as the optic nerve exits here

Question 12

what is the name of the surface of the retina that is on the medial surface (towards the nose) that looks out laterally?

Answer 12

temporal visual field

Question 13

what is the name of the surface of the retina that is on the lateral surface that looks in medially towards the nose?

Answer 13

nasal visual field

Question 14

what axons of the optic nerve decussate

Answer 14

the temporal visual field axons

Question 15

the left optic tract carries vision from where?

look what direction(s)

Answer 15

• the left eye’s nasal visual field and the right eye’s temporal visual field
• thus it looks right

Question 16

the right optic tract carries vision from where?

look what direction(s)

Answer 16

the left eye’s temporal visual field and the right eye’s nasal visual field
-look left

Question 17

what can pituitary tumors cause?

Answer 17

bitemporal vision loss = can see peripheral vision

Question 18

how do the axons of the optic tract get primary visual cortex?

Answer 18

synapse in the lateral geniculate nucleus (of the thalamus) and take the optic radiations back to the occipital lobe

Question 19

the temporal lobe carriers vision for what area?

Answer 19

the temporal lobe (bottom of the brain) carries vison for the sky

Question 20

the parietal lobe carriers vision for what area?

Answer 20

the parietal lobe (top of the brain) carries vision for the ground

Question 21

where is the primary visual cortex located?

Answer 21

• the occipital lobe (calcarine cortex)

- medial surface of the cortex

Question 22

the upper cyrus carries vision for the _______

Answer 22

ground

Question 23

the lower gyrus carries vision for the _______

Answer 23

sky

Question 24

the posterior cerebral artery supplies the _______

Answer 24

calcarine cortex (primary visual field) - occipital lobe
and the temporal lobe

Question 25

the ophthalmic artery supplies the _______

Answer 25

retina, eye, optic nerve

Question 26

the middle cerebral artery supplies the _______

Answer 26

parietal cortex, optic radiations

Question 27

the anterior choroidal artery supplies the _________

Answer 27

optic tract, lateral geniculate nucleus, thalamus

Question 28

macular vision receives blood from ________

Answer 28

both the posterior cerebral artery and the middle cerebral artery

Question 29

what happens if you cut the right optic nerve?

Answer 29

blind in right eye

Question 30

what happens if you cut the optic chiasm? what is this called?

Answer 30

bitemporal hemianopia = no peripheral vision

Question 31

what happens if you cut the right optic tract? what is this called?

Answer 31

left homonymous hemianopia = can't see left field of vision

Question 32

what hoes anopia mean?

Answer 32

loss of vision

Question 33

what happens if you cut both left upper and lower optic radiations? what is it called?

Answer 33

right homonymous hemianopia = loss of right field of vision

Question 34

what happens if you cut the left lower optic radiation? what is it called?

Answer 34

right superior quadrantopia = can't see upper right field of vision

Question 35

what happens if you cut the left upper optic radiation? what is it called?

Answer 35

right inferior quadrantopia = cant see lower right field of vison

Question 36

in regards to the pupillary light reflex, if there is a lesion in CN II of the left eye, what happens when a light is shined in the left eye? What about the right?

Answer 36

light shined in the left eye - nothing happens in both eyes. | Light shined in right eye - both eyes pupils constrict

Question 37

what is double vision called and when does it occur?

Answer 37

diplopia = double vison | -occurs when convergence doesn't happen

Question 38

describe the near response input? output?

Answer 38

input- CN II to lateral geniculate output- 1. CN III - medial rectus 2. CN III - ciliary ganglion - pupillary constrictors

Question 39

what happens to the near response in the right oculomotor lesion?

Answer 39

- right pupil is dilated - pupillary light reflex absent in right eye - near response absent in the right eye - ptosis in right eye

Question 40

what controls pupillary dilation

Answer 40

sympathetic nervous system = hypothalamus

Question 41

what is the sympathetic pathway to dilate the eye?

Answer 41

hypothalamus to T1 to superior cervical ganglion to dilator pupilae

Question 42

what causes Horner's syndrome? Symptoms?

Answer 42

a lesion anywhere in the central or peripheral sympathetic nervous pathway P- ptosis = droopy eyelid A- anhydrosis M- miosis - constricted pupil

Question 43

what are some affects a subdural hematoma can have?

Answer 43

temporal lobe can squeeze the midbrain (small ventricles, misshapen peduncles, compressed midbrain) -causing problems with CN 3 (pupillary light reflex), ptosis, problems with the cerebral peduncles (hyperreflexia, weakness, upper motor neuron damage)

Question 44

the left frontal eye field moves the eyes _________

Answer 44

to the right = contralateral

Question 45

a damaged right frontal field of cortex would cause the eye to move where?

Answer 45

to the right

Question 46

a seizure can cause the field of frontal cortex to move to where?

Answer 46

to the contralateral side

Question 47

what are the two most important cranial nerves of the eye to more in horizontal direction?

Answer 47

CN III - medial rectus of one eye works at the same time as the lateral rectus of the other eye (CN VI)

Question 48

PPRF

Answer 48

paramedian pontine reticular formation

Question 49

where is the PPRF located?

Answer 49

nucleus is located in the pons

Question 50

what does the PPRF control

Answer 50

horizontal eye movements

Question 51

the left cortex make your look _____

Answer 51

right

Question 52

what connects the PPRF to CN III

Answer 52

the medial longitudinal fascicules (MLF)

Question 53

what would happen if there was a problem with the right medial longitudinal Fascicules (MLF)?

Answer 53

- can not adduct right eye when both eyes are trying to look left - medial rectus works fine just not when both eyes are engaged - all other CN III functions are ok

Question 54

in reference to the abducens nucleus, where is the paramedian pontine reticular formation located?

Answer 54

-rostral and ventral to the abducens nucleus

Question 55

cells in the frontal eye field project to the _________ PPRF

Answer 55

contralateral