visual pathway

Question 1

what is the optic nerve developed from?

Answer 1

optic vesicle (an outpocketing of the forebrain)

Question 2

what does the optic nerve do?

Answer 2

transmission of special sensory unfo from retina of eye to primary visual cortex

Question 3

what can the anatomical course of optic nerve be divided into?

Answer 3

• extracranial

- intracranial

Question 4

describe the extracranial portion of the optic nerve

Answer 4

• nerve formed by convergence of axons from retinal ganglion cells
• these cells in turn receive info from photoreceptors of eye
• after formation, nerve leaves through optic canal
• runs along surface of middle cranial fossa

Question 5

describe the start of the intracranial (the visual pathway)

Answer 5

• optic nerves from each eye unite to form optic chiasm

Question 6

what happens at the chiasm?

Answer 6

fibres from nasal (medial) half of each retina cross over to contralateral optic tract
fibres from temprial (lateral) halves remain ipsilateral

Question 7

due to this, what does the left optic tract contain?

Answer 7

contains fibres from left temporal retina and right nasal retina

Question 8

what does the right optic tract contain?

Answer 8

fibres from R temporal retina and R nasal retina

Question 9

where does each optic tract then travel?

Answer 9

travels to its corresponding cerebral hemisphere to reach LGN

Question 10

what is the LGN?

Answer 10

relay system in thalamus

fibres synpase here

Question 11

axons from the LGN then carry visual information via which pathway?

Answer 11

optic radiation

Question 12

what can the optic radiation pathway be divided into?

Answer 12

• upper optic radiation

- lower optic radiation

Question 13

what does the upper optic radiation carry?

Answer 13

• carries fibres from superior retinal quadrants (corresponding to inferior visual field quadrants)
• travels through parietal lobe to reach visual cortex

Question 14

what does the lower optic radiation carry?

Answer 14

• carriers fibres from inferior retinal quadrants (corresponding to superior visual field quadrants)
• travels through temporal lobe via Meyers loop to reach visual cortex

Question 15

why does a pituitary adenoma affect vision?

Answer 15

gland lies close to optic chiasm

enlargement of pituitary gland can affect functioning of optic nerve

Question 16

what does compression of the optic chiasm particularly affect?

Answer 16

fibres that are crossing over from nasal half of each retina

causes bitemporal hemianopia