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Neuroscience > Visual Pathway > Flashcards

Visual Pathway Flashcards

1
Q

M ganglion cells are also called

A

magnocellular cells, parasol ganglion cells

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2
Q

What are the features of M ganglion cells?

A

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

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3
Q

M ganglion cells synapse in

A

magnocellular layer of the LGN of the thalamus

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4
Q

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

A

motion; visual acuity

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5
Q

M ganglion cells make up _____% of ganglion cells

A

10%

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6
Q

P ganglion cells are also called

A

parvocellular, midget ganglion cells

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7
Q

What are the features of P ganglion cells?

A

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

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8
Q

P ganglion cells encode information about

A

colour vision and visual acuity

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9
Q

P ganglion cells synapse in

A

Parvocellular layers of the LGN of the thalamus

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10
Q

P ganglion cells make up _____% of ganglion cells

A

80%

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11
Q

Ganglion cell axons form the

A

optic nerve

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12
Q

What are the 5 different targets of ganglion cell axons?

A

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

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13
Q

The most important target of ganglion cells is the

A

LGN in the thalamus

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14
Q

Projections of ganglion cells to the LGN form the

A

visual pathway

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15
Q

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

A

pupil responses

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16
Q

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

A

circadian rhythm

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17
Q

Projections of ganglion cells to the superior colliculus are responsible for

A

eye movements

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18
Q

Nasal retinal ganglion cells see the ______ visual field

A

temporal

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19
Q

Temporal retinal ganglion cells see the ______ visual field

A

nasal

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20
Q

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

A

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

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21
Q

The right visual cortex receives input from

A

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

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22
Q

The left visual cortex receives input from

A

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

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23
Q

Which fibres cross at the optic chiasm?

A

nasal

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24
Q

Bitemporal visual field defect is a classic sign of

A

lesion of the chiasm eg pituitary tumour

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25
Q

T/F All sensory information is relayed through the thalamus

A

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

26
Q

Layers 1 and 2 of the LGN are

A

Magnocellular layers, targeted by M ganglion cells

27
Q

Layers 3-6 of the LGN are

A

Parvocellular layers, targeted by P ganglion cells

28
Q

How is information received at the LGN?

A

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

29
Q

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

A

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

30
Q

V1 is located

A

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

31
Q

What is the retinotopic organization of V1?

A

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

32
Q

Lesions that affect only one eye must be occurring

A

before the chiasm

33
Q

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

A

at the chiasm

34
Q

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

A

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

35
Q

Macular sparing occurs when

A

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)

36
Q

Bitemoporal heminanopia indicates

A

chiasm lesion

37
Q

Homonymous hemianopia indicates

A

optic tract lesion

38
Q

Homonymous quadranopia indicates

A

lesion of the optic radiation

39
Q

T/F Ganglion cells require photoreceptors to respond to light

A

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

40
Q

Ganglion cells that are intrinsically light sensitive synapse in the

A

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

41
Q

ipGCs

A

intrinsically photosensitive ganglion cells/melanopsin ganglion cells

42
Q

ipGCs contain

A

Melanopsin, similar to photopigments of photoreceptors

43
Q

Light activation of melanopsin results in

A

depolarization of ipGCs

44
Q

ipGCs provide information about

A

how much light is in the environment

45
Q

Function of ipGCs is important in

A

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

46
Q

What allows people who are totally blind to become jetlagged?

A

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

47
Q

What is the direct pupil response?

A

Constriction of the pupil in response to direct light

48
Q

What is the consensual pupil response?

A

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

49
Q

Pupil responses are dependent on

A

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

50
Q

Which ganglion cells are responsible for pupil responses?

A

ipGCs/melanopsin ganglion cells

51
Q

Melanopsin GCs project to which nucleus?

A

Optical Pretectal Nucleus (OPN)

52
Q

What causes an afferent pupil defect?

A

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

53
Q

What causes an efferent pupil defect?

A

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

54
Q

T/F Blind individuals do not exhibit pupil responses

A

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

55
Q

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

A

Edinger-Westfal nucleus

56
Q

From the Edinger-Westfall nucleus, information travels via

A

CN III to the ciliary ganglion

57
Q

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

A

CN III innervating constrictor pupillae

58
Q

How do ipGCs/melanopsin GCs regulate circadian rhythm?

A

Project to the surpachiasmatic nucleus of the hypothalamus about light levels

59
Q

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

A

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

60
Q

Migraine pain is attributed to

A

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

Neuroscience (15 decks)

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