Mod 11 Visual System

Question 1

What is a visual field?

Answer 1

the portion of space that can be viewed from the retina when the eye is fixated straight ahead (what we see in the environment)

Question 2

What is a retinal field?

Answer 2

the portion of retina that alters its firing rate in reasons to a stimulus (picks up light and color)

Question 3

What is the relationship between visual and retinal field?

Answer 3

reverse and inverted relationship (temporal visual field is the nasal retinal field)

Question 4

How are visual deficits named?

Answer 4

according to visual field

Question 5

How is the retina divided?

Answer 5

• lateral: temporal
• medial: nasal
• superior and inferior half

Question 6

What are rods and cones and where are they located?

Answer 6

• deepest retinal layer
• photoreceptors

Question 7

What are the bipolar cells in the retina and where are they located?

Answer 7

• intermediate retinal layer
• info integrating neurons

Question 8

What are the ganglion cells in the retina and where are they located?

Answer 8

• superficial layer
• info integrating neurons that exit the eyeball as the optic nerve (CN II)

Question 9

What is the scotopic-rod system?

Answer 9

• system that works at low levels of light and is sensitive to light, insensitive to color
• limited resolution

Question 10

What does the rod system help you do?

Answer 10

help see in the night vision

Question 11

What is the photopic-cone system?

Answer 11

• system that works at high levels of light and is responsible for seeing color, sharp vision, and acuity
• color, clear

Question 12

What color do rods see?

Answer 12

black, white, grey

Question 13

What do rods and cones respond to?

Answer 13

respond to photons and signal retinal ganglion cells

Question 14

How many rods and cones are in each eye?

Answer 14

80-110 million rods

4-5 million cones

Question 15

Where are cones the densest in the eye?

Answer 15

densest in the macula

peripheral layers are where cones lie

Question 16

What is the center of the macula?

Answer 16

fovea: area keenest vision

Question 17

What is the memory trick remember cone’s role in the eye?

Answer 17

cones, color, clear

rods: light, peripheral

Question 18

What is the role of ganglion cells in the eye?

Answer 18

center for retinal processing as it converges onto these cells

these cells form the optic nerve

Question 19

Where do M Type ganglion cells project?

Answer 19

project to the magnocellular layer of the lateral geniculate body

Question 20

What are M Type ganglion cells concerned with?

Answer 20

patterns and contrast

Question 21

Where do P Type ganglion cells project?

Answer 21

parvocellular layer of lateral geniculate body

Question 22

What are p type ganglion cells concerned with?

Answer 22

color transmission

Question 23

What is the blind spot of the eye?

Answer 23

an elevated circular retinal region where ganglion cell axons leave the eye as the optic nerve

does not have rods and cones

Question 24

What is the visual pathway?

Answer 24

receptors > bipolar cells(1st order) > ganglion cells (2nd order)/optic nerve > thalamus lateral geniculate body (3rd) > primary visual cortex

Question 25

Which retinal field crosses in the optic chiasm?

Answer 25

nasal retinal fields

Question 26

Which part of the nervous system is the optic nerve a part of?

Answer 26

CNS

Question 27

What is the structure of the optic nerve?

Answer 27

- myelinated by oligodendrocytes - invested by dural sheet of CNS - surrounded by CSF

Question 28

Where do optic nerve fibers originate?

Answer 28

originate in ipsilateral eye

Question 29

What retinal fields are in a optic tract fiber?

Answer 29

temporal retinal field of ipsilateral eye and nasal retinal field of contralateral eye

Question 30

Where do most axons of the optic tract synapse?

Answer 30

on third order neurons in the lateral geniculate body of the thalamus

Question 31

Where does the LGB input come from?

Answer 31

10-20% from retina rest comes from brainstem reticular info (arousal and consciousness) and visual cortex

Question 32

Where do third order neurons go?

Answer 32

project from the LGB as optic radiation to the occipital lobe

Question 33

Where do dorsal and ventral axons project in the brain?

Answer 33

dorsal: directly to occipital lobe ventral: anteriorly and downward as Meyer's loop

Question 34

What is the inversion of visual fields in the eye?

Answer 34

upper visual fields project to lower retinal quadrants nasal to temporal

Question 35

Where does lower visual field input go in the visual pathway?

Answer 35

upper retinal quadrant goes dorsal to the primary visual cortex

Question 36

Where does upper visual field input go in the visual pathway?

Answer 36

lower retinal field goes to Meyer's loop then PVC

Question 37

How do you remember what visual field goes to Meyer's loop?

Answer 37

What I see higher goes meyer

Question 38

What does the calcarine sulcus do?

Answer 38

splits retinal field input

Question 39

Which broadmann's area is the PVC?

Answer 39

BA 17

Question 40

Where do some optic radiation axons terminate?

Answer 40

un visual association cortex BA 18 and 19

Question 41

Where does the dorsal pathway of visual processing go and what does it process?

Answer 41

- PVC to parieto-occipital cortex - WHERE in the visual field an event occurred

Question 42

Where does the ventral pathway of visual processing go and what does it process?

Answer 42

- primary visual cortex to occipito-temporal cortex - WHAT the object in the visual field is

Question 43

Where do some optic tract axons terminate?

Answer 43

hypothalamus: role in circadian rhythm

Question 44

Why do some optic tract axons bypass the LGB and project to the midbrain?

Answer 44

superior coliculus: visual grasp reflex pretectal area: visual light reflex

Question 45

How does aging affect the eye?

Answer 45

presbyopia develops - age related loss of accommodation power (change focal length) - lens hardens - cannot focus on near objects

Question 46

What is age related macular degeneration?

Answer 46

6th decade of life - loss of central vision and acuity - affects cone system - leading cause of blindness in elderly

Question 47

How do you assess the visual system?

Answer 47

- snellen chart - ophthalmic inspection - pupillary light reflex - quadrant assessment

Question 48

What is found in ophthalmic inspection?

Answer 48

optic dic swelling with elevated intracranial pressure due to excessive CSF can cause blurred, double, or transient full vision loss

Question 49

What is hemianopsia?

Answer 49

visual deficit of one-half of visual field ex: temporal half

Question 50

What is quadrantanopsia ?

Answer 50

visual deficit of one quadrant of the visual field ex: upper temporal quadrant

Question 51

What is bitemporal hemianopsia?

Answer 51

lesion to optic chiasm causing the loss of peripheral vision (severs nasal retinal fields)

Question 52

What is contralateral homonymous hemianopsia?

Answer 52

lesion impacting optic tracts - cannot see temporal retinal field of ipsilateral eye and nasal retinal field of contralateral eye

Question 53

What is monocular scotoma?

Answer 53

individual blind spot

Question 54

What is monocular visual loss?

Answer 54

whole eye blindness

Question 55

What is contralateral inferior quadrantanopsia?

Answer 55

lower quadrant loss

Question 56

What is contralateral superior quadrantanopsia?

Answer 56

upper quadrant loss

Question 57

What is macular sparing?

Answer 57

vascular lesion to occipital lobe - both MCA and PCA nourish cortical area for macula - if one is occluded, the other still gives blood leaving you with central vision

Question 58

What is amaurosis fugax?

Answer 58

transient ischemic attack of the retina

Question 59

What is optic neuritis?

Answer 59

inflammatory demyelination disorder related to MS - symptoms of: eye pain, decreased acuity, and impaired color vision, altered light reflex - recovery is common

Question 60

What is visual agnosia?

Answer 60

deficit associated with higher cortical processing when you can perceive but not understand what you see (ventral pathway)

Question 61

What is prosopagnosia?

Answer 61

deficit associated with higher cortical processing that causes face blindness due to damage to the occipitotemporal cortex

Question 62

What are the first signs of MS?

Answer 62

optic neuritis, scotoma, and visual field deficits due to the loss of oligodendrocytes

Question 63

How do migraines connect with the visual pathway?

Answer 63

prodromal phase of migraine involves visual cortex - 1/3 experience visual aura - 10% experience scintillating scotoma where the blindspots are wavy, jagged, large, and bilateral in presentation