Flashcards in visual pathway Deck (16)
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?
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?
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