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Flashcards in visual pathway Deck (16)
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what is the optic nerve developed from?

optic vesicle (an outpocketing of the forebrain)


what does the optic nerve do?

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


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

- extracranial
- intracranial


describe the extracranial portion of the optic nerve

- 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


describe the start of the intracranial (the visual pathway)

- optic nerves from each eye unite to form optic chiasm


what happens at the chiasm?

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


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

contains fibres from left temporal retina and right nasal retina


what does the right optic tract contain?

fibres from R temporal retina and R nasal retina


where does each optic tract then travel?

travels to its corresponding cerebral hemisphere to reach LGN


what is the LGN?

relay system in thalamus
fibres synpase here


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

optic radiation


what can the optic radiation pathway be divided into?

- upper optic radiation
- lower optic radiation


what does the upper optic radiation carry?

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


what does the lower optic radiation carry?

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


why does a pituitary adenoma affect vision?

gland lies close to optic chiasm
enlargement of pituitary gland can affect functioning of optic nerve


what does compression of the optic chiasm particularly affect?

fibres that are crossing over from nasal half of each retina
causes bitemporal hemianopia