Visual System Flashcards
What is the first order neurone in the visual system?
Bipolar cells
Where is the second order neurone in the visual system?
ganglion cells - axon forms optic nerve
what are the interneurones of the retina?
horizontal cells
amacrine cells
Objects in one lateral half of the visual field form images on the …… half of the ipsilateral retina and the ….. half of the contralateral retina.
nasal
temporal
At the chiasm, which part of the retinal field will decuss to the contralateral side?
Nasal side
Where does the second order neurones of the visual system, i.e. the optic nerves terminate?
lateral geniculate nucleus of the thalamus
A small number of fibres leave the optiv nerve before reaching the lateral geniculate, where do they do?
Pretectal area
superior colliculus
- mediation of the pupillary light reflex
What happens in the visual association cortex?
interpretation of visual images, recognition, depth perception, and colour vision
IMPORTANT NOTE about the visual field
objects in either half (left or right) of the visual field produce images upon the nasal hemiretina of the ipsilateral eye and the temporal hemiretina of the contralateral eye
The combination of images from both eyes is necessary for …
stereoscopic vision (depth perception)
Fibres representating the upper part of the visual field sweep into the temporal lobe, called the ……
Meyer’s loop
upper left quadrant of the visual field is represented in the …… …….. quadrant of the visual cortex
lower right
Diagram of the eye
What is the consequence of raised intraocular pressure (glaucoma)?
problems with blood supply to the eye and blindness
Ocular fluid is secreted by the……
ciliary body
Which reflexes are initiated by hte nociceptive sensory axons of the corneal epithelium?
The corneal reflex, via the ophthalmic division of V (sensory)
closing the eye reflex - motor branch of VII to orbicularis oculi
Where does the cornea get it’s nutrition
tears
The retina is an extension of which part of the brain?
diencephalon
What does each photoreceptor cell synapse with?
Two types of bipolar cell
an “on” bipolar activated in the light (but inhibited in the dark by glutamate), and an “off” bipolar activated in the dark.
Thus the visual pathway detects both light and the absence of light.
Important action of the pigment epithelium, what is it?
Destroys worn out rod and cone membrane (this mechanism fails in retinitis pigmentosa, causing debris accumulation and blindness)
What do horizontal cells do?
Form inhibitory surrounds to areas of maximum brightness, increasing image contrast
What do amacrine cells do?
Further process the image, allowing detection of movement, adjusting brightness and other complex image features etc.
Meyer’s loop is part of the ….
visual radiation
Visual field defects
What is this called?
Bitemporal hemianopia
What’s the name of this?
Homonymous hemianopia
