Neurology of the Visual System Flashcards
(85 cards)
7 landmarks of the visual pathway?
- Eye
- Optic nerve- Ganglion nerve fibres
- Optic chiasm- Half of the nerve fibres cross here
- Optic tract- Ganglion nerve fibres exit as the optic tract
- Lateral Geniculate Nucleus- Ganglion nerve fibres synapse here
- Optic Radiation- 4th order neuron
- Primary Visual Cortex or Striate Cortex- within the occipital lobe
1st order neurons of the retina?
rod and cone photoreceptors
2nd order neurons of the retina?
retinal bipolar cells
3rd order neurons of the retina?
retinal ganglion cells
afferent innervation of the retina is via the …
optic nerve
Partial decussation of the optic nerve occurs in the …
optic chasm
Destination of the optic nerve/
Lateral geniculate nucleus
What is the receptive field of a neuron
a retinal space within which incoming light can alter the firing pattern of a neuron
In a retinal ganglion cell there is a convergence of XX from YY
receptive fields
neighbouring photoreceptors
Cone system divergence is [more/less] than rod system convergence
Less
- Central retina convergence is [more/less] than peripheral retina convergence
Less
Low convergence:
receptive field size?
Visual acuity level?
Light sensitivity?
Small receptive field, fine visual acuity, low light sensitivity
High convergence:
receptive field size?
Visual acuity level?
Light sensitivity?
Large receptive field, coarse visual acuity, high light sensitivity
What cell is between the rod/cone photoreceptor and the retinal ganglion cell
retinal Bipolar cells
ON-centre ganglions are stimulated by and inhibited by light where?
- Stimulated by light at the centre of the receptive field
- Inhibited by light on the edge of the receptive field
OFF-centre ganglions are stimulated by and inhibited by light where?
- Inhibited by light at the centre of the receptive field
- Stimulated by light on the edge of the receptive field
What are on and off centre ganglion cells important for
contrast sensitivity and enhanced edge detection
Fibres that cross in the optic chiasm originate in the X retina and correspond to the Y visual field
nasal
temporal
LESION AT OPTIC CHIASMA causes…
BITEMPORAL HEMIANOPIA
LESION posterior to the OPTIC CHIASMA causes…
- Right sided lesion- left homonymous hemianopia in both eyes
- Left sided lesion- right homonymous hemianopia in both eyes
7 types of visual field defects
monocular blindness bitemporal hemianopia right/left nasal hemianopia right/left homonymous hemianopia TR/TL/BR/BL quadrant-anoxia Macular sparing homonymous hemianopia
Cause of bitemporal hemianopia
pituitary gland tumour
Cause of bitemporal hemianopia
stroke
Primary visual cortex is located along the …
calcarine sulcus within occipital lobe