Visual Pathway

Question 1

What kind of glutamate receptors can bipolar cells express?

Answer 1

Metabotropic

Ionotropic

Question 2

Why are there different types of ganglion cells?

Answer 2

Each type provides info for different stream of vision

Question 3

What are two types of ganglion cells?

Answer 3

M/parasol

P/midget

Question 4

Are M and P ganglion cells ON or OFF ganglion cells?

Answer 4

Each type has ON and OFF type

• M ON
• M OFF
• P ON
• P OFF

Question 5

Describe M ganglion cells

Answer 5

Motion
Large cell bodies
Long processes
Covers large area of retina
10-15% of ganglion cells
Especially prone to disease

Question 6

Describe P ganglion cells

Answer 6

Colour vision
Visual acuity
Small cell bodies
Short processes
80% of ganglion cells

Question 7

What are the targets of ganglion cell axons?

Answer 7

Lateral geniculate nucleus (LGN) in thalams
Pretectum in midbrain
Suprachiasmatic nucleus in hypothalamus
Superior colliculus
Various other nuclei of thalamus

Question 8

Why do ganglion cell axons project to the LGN?

Answer 8

Major target of most ganglion cells

Visual pathway

Question 9

Why do ganglion cell axons project to the pretectum?

Answer 9

Pupil responses

Question 10

Why do ganglion cell axons project to the suprachiasmatic nucleus?

Answer 10

Circadian rhythm

Question 11

Why do ganglion cell axons project to the superior colliculus?

Answer 11

Eye movements

Question 12

Why do ganglion cell axons project to the nuclei in the thalamus other than the LGN?

Answer 12

Photophobia

Question 13

What is the optic chiasm?

Answer 13

Fibres from right and left optic nerves combine

Question 14

How many ganglion fibres cross at the optic chiasm?

Answer 14

Half

Question 15

Where is the optic chiasm?

Answer 15

Base of brain anterior to pituitary

Question 16

From which hemifield does the nasal retina receive light information?

Answer 16

Temporal hemifield

Question 17

From which hemifield does the temporal retina receive light information?

Answer 17

Nasal hemifield

Question 18

Which fibres cross at the optic chiasm?

Answer 18

Nasal fibres

Question 19

Which hemisphere views each hemifield?

Answer 19

Right visual hemifield viewed by left hemisphere

Left visual hemifield viewed by right hemisphere

Question 20

What part of the visual field does a stroke affect when it’s in the visual cortex?

Answer 20

Half of each field in each eye, rather than one entire eye

Question 21

What is the name of the tract after the optic chiasm?

Answer 21

Optic tract

Question 22

Where do ganglion cell axons in the optic tract synapse?

Answer 22

LGN

Question 23

How many neurons are there in the visual pathway?

Answer 23

2

Question 24

Why is the anatomical position of the optic chiasm relevant to pathology?

Answer 24

Pituitary gland just below

Condition affecting it can affect chiasm; eg: in pituitary macroadenoma

Question 25

What is the classic presentation of a person's visual field when they have a pituitary macroadenoma?

Answer 25

Bitemporal hemianopia

Question 26

Which hemifields are affected in bitemporal hemianopia?

Answer 26

Temporal hemifields

Question 27

Where do second order neurons in the visual pathway arise from?

Answer 27

LGN

Question 28

How is information in the LGN segregated?

Answer 28

By eye and ganglion cell type

Question 29

How many layers are there in the LGN?

Answer 29

6

Question 30

What are the types of cells in the LGN?

Answer 30

Magnocellular | Parvocellular

Question 31

Where do M ganglion cells synapse?

Answer 31

Magnocellular layers: 1 and 2

Question 32

Where do P ganglion cells synapse?

Answer 32

Parvocellular layers: 3-6

Question 33

Which layers receive input from the right eye?

Answer 33

2, 3, 5

Question 34

Which layers receive input from the left eye?

Answer 34

1, 4, 6

Question 35

Where do LGN neurons project to?

Answer 35

Primary visual cortex (V1)

Question 36

What is the Broddman's area of V1?

Answer 36

Area 17

Question 37

Where in the brain is the primary visual cortex?

Answer 37

Occipital lobe around calcarine fissure - On medial aspect - Upper and lower banks around fissure

Question 38

How is information organised in the primary visual cortex?

Answer 38

Retinotopic organisation = neighbouring cells within retina project to neighbouring cells in LGN and visual cortex

Question 39

Which part of the visual cortex receives information from the macula?

Answer 39

Most posterior part = macular cortex

Question 40

Which part of the visual cortex receives information from the peripheral retina?

Answer 40

Anterior parts

Question 41

What visual field is affected when there's a lesion in the right optic nerve?

Answer 41

Right eye visual field

Question 42

What visual field is affected when there's a lesion at the optic chiasm?

Answer 42

Temporal hemifields

Question 43

What visual field is affected when there's a lesion in the right optic tract?

Answer 43

Left visual hemifields

Question 44

What visual field is affected when there's a lesion in the right optic radiation?

Answer 44

Upper left quadrant of visual fields of both eyes

Question 45

How can the visual field of the macula be spared when there's a lesion in the right visual cortex?

Answer 45

Only happens with vascular event Macular cortex supplied by different blood supply than rest of occipital lobe If infarct in vessel supplying rest of occipital lobe, then macular vision spared

Question 46

What is the tract from the LGN to the primary visual cortex called?

Answer 46

Optic radiation

Question 47

What are intrinsically photosensitive ganglion cells?

Answer 47

Small population of ganglion cells containing visual pigment = melanopsin Light activation of melanopsin > intrinsically photosensitive ganglion cells depolarise

Question 48

What are the functions of intrinsically photosensitive ganglion cells?

Answer 48

``` Circadian rhythm Sleep regulation Pupil responses General info about light levels Light allodynia ```

Question 49

What is light allodynia?

Answer 49

Photophobia associated with - Migraine - Ocular injury - Infection

Question 50

What do pupil responses depend on?

Answer 50

Being able to detect light | Functioning iris

Question 51

What are the two muscles of the iris?

Answer 51

Dilator pupillae | Sphincter pupillae

Question 52

Where is one projection of melanopsin ganglion cells?

Answer 52

Optical pretectal nucleus (OPN)

Question 53

Where do ganglion fibres heading to the OPN diverge from the visual pathway?

Answer 53

After optic chiasm | Before thalamus

Question 54

Where do neurons from the OPN synapse with to control pupil responses?

Answer 54

Edinger-Westfal nucleus

Question 55

Which side of the brain does the OPN send fibres to in order to provide information for pupil motor responses?

Answer 55

Ipsilateral | Contralateral

Question 56

At what age do babies start to develop circadian rhythms?

Answer 56

6-12 weeks

Question 57

Where do intrinsically photosensitive ganglion cells project to in order to provide information for the circadian rhythm?

Answer 57

Suprachiasmatic nucleus (SCN) in hypothalamus

Question 58

What is the effect of light in migraines?

Answer 58

Worsens pain

Question 59

What is the pain pathway for migraines?

Answer 59

Thought to be due to nerves signalling from dura Pain from dura carried by trigeminal nerve Dura > trigeminal nerve > brainstem > posterior nucleus of thalamus

Question 60

Why does light cause pain to worsen in migraines?

Answer 60

Intrinsically photosensitive ganglion cells synapse in posterior nucleus of thalamus > influence pain fibres