Visual Pathway

Question 1

M ganglion cells are also called

Answer 1

magnocellular cells, parasol ganglion cells

Question 2

What are the features of M ganglion cells?

Answer 2

large cell bodies with large dendritic trees; synapse in the magnocellular layer in the LGN of the thalamus

Question 3

M ganglion cells synapse in

Answer 3

magnocellular layer of the LGN of the thalamus

Question 4

M ganglion cells provide information about _______ and less so about _________

Answer 4

motion; visual acuity

Question 5

M ganglion cells make up _____% of ganglion cells

Answer 5

10%

Question 6

P ganglion cells are also called

Answer 6

parvocellular, midget ganglion cells

Question 7

What are the features of P ganglion cells?

Answer 7

small cell bodies and small dendritic trees; synapse in parvocellular layers of LGN in thalamus

Question 8

P ganglion cells encode information about

Answer 8

colour vision and visual acuity

Question 9

P ganglion cells synapse in

Answer 9

Parvocellular layers of the LGN of the thalamus

Question 10

P ganglion cells make up _____% of ganglion cells

Answer 10

80%

Question 11

Ganglion cell axons form the

Answer 11

optic nerve

Question 12

What are the 5 different targets of ganglion cell axons?

Answer 12

LGN (thalamus); pretectum (midbrain); suprachiasmatic nucleus (hypothalamus); superior colliculus (eye movements); various thalamic nuclei

Question 13

The most important target of ganglion cells is the

Answer 13

LGN in the thalamus

Question 14

Projections of ganglion cells to the LGN form the

Answer 14

visual pathway

Question 15

Projections to the pretectum in the midbrain from ganglion cells play a role in

Answer 15

pupil responses

Question 16

Projections of ganglion cells to the suprachiasmatic nucleus of the hypothalamus are involved in

Answer 16

circadian rhythm

Question 17

Projections of ganglion cells to the superior colliculus are responsible for

Answer 17

eye movements

Question 18

Nasal retinal ganglion cells see the ______ visual field

Answer 18

temporal

Question 19

Temporal retinal ganglion cells see the ______ visual field

Answer 19

nasal

Question 20

T/F Nasal fibres are the only fibres that cross at the optic chiasm

Answer 20

True; temporal fibres run ipsilateral and DO NOT cross at the ciasm

Question 21

The right visual cortex receives input from

Answer 21

the left visual field (L nasal retina, R temporal retina)

Question 22

The left visual cortex receives input from

Answer 22

the right visual field (L temporal retina, R nasal retina)

Question 23

Which fibres cross at the optic chiasm?

Answer 23

nasal

Question 24

Bitemporal visual field defect is a classic sign of

Answer 24

lesion of the chiasm eg pituitary tumour

Question 25

T/F All sensory information is relayed through the thalamus

Answer 25

False; all sensory information EXCEPT olfaction is relayed through the thalamus

Question 26

Layers 1 and 2 of the LGN are

Answer 26

Magnocellular layers, targeted by M ganglion cells

Question 27

Layers 3-6 of the LGN are

Answer 27

Parvocellular layers, targeted by P ganglion cells

Question 28

How is information received at the LGN?

Answer 28

one of the M cell layers is from one eye, the other from the other eye; two of the P cell layers is from one eye, the other 2 are from the other eye - almost alternating

Question 29

T/F M and P inputs from each eye mix at the LGN

Answer 29

False; there is no mixing of information from each eye at the LGN

Question 30

V1 is located

Answer 30

on the medial surface of the occipital lobe, around the calcacrine fissure

Question 31

What is the retinotopic organization of V1?

Answer 31

most central vision projects to the most posterior part of V1; as you move anteriorly along the calcarine fissure inputs are more peripheral

Question 32

Lesions that affect only one eye must be occurring

Answer 32

before the chiasm

Question 33

If visual field defects are present on opposite sides (bitemporal), the lesion is

Answer 33

at the chiasm

Question 34

If visual defects are on the same side of each eye, the lesion is

Answer 34

behind the chiasm (optic tract, optic radiations, or in V1)

Question 35

Macular sparing occurs when

Answer 35

a vascular accident damages the MCA (supplies more peripheral visual inputs to V1) but spares the PCA and therefore flow to the macular cortex of V1 (most posterior)

Question 36

Bitemoporal heminanopia indicates

Answer 36

chiasm lesion

Question 37

Homonymous hemianopia indicates

Answer 37

optic tract lesion

Question 38

Homonymous quadranopia indicates

Answer 38

lesion of the optic radiation

Question 39

T/F Ganglion cells require photoreceptors to respond to light

Answer 39

False; some ganglion cells contain a protein melanopsin which like rhodopsin (a photopigment) and are intrinsically light-sensitive (ipGCs)

Question 40

Ganglion cells that are intrinsically light sensitive synapse in the

Answer 40

suprachiasmatic nucleus (hypothalamus), pretectum (midbrain), and posterior nucleus of the thalamus

Question 41

ipGCs

Answer 41

intrinsically photosensitive ganglion cells/melanopsin ganglion cells

Question 42

ipGCs contain

Answer 42

Melanopsin, similar to photopigments of photoreceptors

Question 43

Light activation of melanopsin results in

Answer 43

depolarization of ipGCs

Question 44

ipGCs provide information about

Answer 44

how much light is in the environment

Question 45

Function of ipGCs is important in

Answer 45

circadian rhythm, sleep regulation, pupil responses, light level information, and light allodynia (photophobia)

Question 46

What allows people who are totally blind to become jetlagged?

Answer 46

ipGCs - because they tell us how much light is in our environment and regulate circadian rhythms

Question 47

What is the direct pupil response?

Answer 47

Constriction of the pupil in response to direct light

Question 48

What is the consensual pupil response?

Answer 48

Constriction of the pupil in response to light shone on the other pupil

Question 49

Pupil responses are dependent on

Answer 49

the ability to detect light (melanopsin ganglion cells), and functioning of the iris (sphincter and dilator pupillae muscles)

Question 50

Which ganglion cells are responsible for pupil responses?

Answer 50

ipGCs/melanopsin ganglion cells

Question 51

Melanopsin GCs project to which nucleus?

Answer 51

Optical Pretectal Nucleus (OPN)

Question 52

What causes an afferent pupil defect?

Answer 52

A lesion on the pathway from the melanopsin ganglion cell to the midbrain

Question 53

What causes an efferent pupil defect?

Answer 53

A lesion on the pathway between the Edinger-Westfal nucleus and the eye (via ciliary ganglion)

Question 54

T/F Blind individuals do not exhibit pupil responses

Answer 54

False; the constriction is just less but they still have ipGCs/melanopsin GCs

Question 55

From the pretectal nucleus, projections in the pupil response go to the

Answer 55

Edinger-Westfal nucleus

Question 56

From the Edinger-Westfall nucleus, information travels via

Answer 56

CN III to the ciliary ganglion

Question 57

From the ciliary ganglion, constriction in the pupil reflex is produced by

Answer 57

CN III innervating constrictor pupillae

Question 58

How do ipGCs/melanopsin GCs regulate circadian rhythm?

Answer 58

Project to the surpachiasmatic nucleus of the hypothalamus about light levels

Question 59

How do ipGCs/melanopsin GCs relate to photophobia in migraines?

Answer 59

ipGCs target the posterior nucleus of the thalamus; this is the nucleus important in the pain pathway of migraines

Question 60

Migraine pain is attributed to

Answer 60

pain originating in the dura/meninges; projects to the posterior nucleus of the thalamus along with ipGCs (hence photophobia)