20 Vision Flashcards
Locate the pupil on the eye and explain its purpose…
The opening that allows light to enter the eye and reach the retina
Locate the Iris and expalins its purpose
circular muscle that controls the size of the purple
Locate the Cornea and explain its purpose
The transparent surface that covers the pupil and iris
what is the sclera? location and purpose
white of the eye, continuous with the cornea
What is the lens? location and purpose
helps focus rays of light on the retina
what is the retina? location and purpose
the internal lining of the rear two-thirds of the eye, the retina coverts images into electrical impulses, which are sent to the brain.
What is the macula? location and purpose
the central area of the retina that is specialised for central vision
what is the fovea? location and purpose
the visual image received by the fovea is at least distorted; marks the centre of the retina and the centre of the macula
what is the optic nerve? location and purpose.
made up of axons of the retinal ganglion cells; carries impulses for vision from the retina towards the brain
how many extrocular muscels are there in the eye?
3
what electromagnetic wavelength can be detected by the human eye
400-700nm
Flow of visual information in the retnia
photoreceptors –> bipolar cells –> ganglion cells
why do we have a blind spot?
there are no photoreceptors, therefore the sensation of light can not occur.
What is the side of the eye closest to the nose called? and then the other side
Nasal hemiretina & temporal hemiretina
What side of your visual field is the blind spot on?
temporal hemiretinal
What is the optic chasm?
Where the axons of the ganglion cells cross the midline
Do the axons of the ganglion cells located in each temporal hemi-retina cross the optic chasim?
no
What happens if the left optic nerve is cut?
left eye vision will be lost, resulting in a loss of left peripheral vision.
what happens if the optic chasm is transected?
Peripheral vision is lost bilaterally
what happens if the left optic tract is cut?
vision of the right hemifield will be lost completely. Homonymous hemianopsia
what are the axons of the ganglion cells called?
the optic nerve before they cross the optic chassim
optic tract after the optic chiasm
where do the axons of the optic track project too?
Superior colliculus?
Thalamus (Geniculate nucelus)
The retinotectal pathway
retina –> superior colliculus
Retinogenisulostriate pathway
retina –> thalamus –> primary visual cortex
What visual information does the right LGN track receive? then the left track
left, then right. oppisote
is the LGN retnotopically mapped?
yes
is the Primary visual cortex retinotopically mapped?
yes
cortical vision pathway
retina
LGN
primary visual cortex in the occipital love
extrastriate cortex in the occipital, temporal and parietal lobes
What happens when TMS is distributed over the primary visual cortex?
elicit light sensations in the absence of any stimuli
What did the study on ecstasy and V1 excitability show?
The goal was to measure the excitability of the primary visual cortex and make comparisons.
Results 1: ectacy group had a significantly lower phosphine threshold than participants in the control group. Negatively correlated with phosphine threshold.
Results 2: phosphene threshold of participants who had hallucinations was significantly lower than the phonsoehen threshold of participants who did not hallucinate.
what is the ventriloquist illusion?
mislocalisation towards a synchronous but spatially discrepant visual event
