Flashcards in Lecture 5: The Visual Pathway Deck (19):
What does the non-neuronal layer of the retina consist of?
What is the function of the pigmented epithelium?
Sits against the choroid of the eye ball and is light absorbing. It is important in maintaining the metabolic activity of the photoreceptors which it surrounds by the way of melanin filled microvilli. It also provides capillaries to the photoreceptors.
What are the features of the 3 neuron chain from photoreceptor to cortex.
- Primary and secondary order neurons in retina
- Outgrowth of diencephalon
- Primary Bipolar cells
- Secondary Ganglion cells
- Axons of the ganglion cells run over
retina to optic disk/blind spot
- Form optic nerve
- Optic nerve to Lateral geniculate nucleus (thalamus)
- Then via optic radiation to primary
Which part of the thalamus does the optic nerve project to?
Lateral geniculate nucleus
Why does a rise in CSF cause papilloedema?
The optic nerve is an outgrowth of the CNS (diencephalon), thus is completely encapsulated by meninges and CSF. A rise in CSF pressure will cause swelling of the optic disc.
What is the visual association cortex?
Helps in the understanding of visual information (e.g. facial recognition, colours etc)
What happens to visual information in the left and right lateral geniculate nuclei?
Synthesises all visual information from left and right hand sides.
Which hemisphere receives information from the left visual field?
Which part of the brain receives upper visual field information?
Lower bank of calcarine sulcus (and vice versa)
What is a scotoma?
A localised patch of blindness?
What is anopia?
Loss of one or more quadrants of the visual field.
What is hemianopia?
Half of the visual field lost
What is quadrantanopia?
Quarter of the visual field is lost
What does homonymous mean?
Visual field losses are similar on both sides of the eyes.
What does heteronymous mean?
Visual field losses are on different sides
Where do approx 10% of optic tract fibres project to?
Take a medial root to the pre-tectal area (midbrain).
Which cranial nerve does the pupillary light reflex require?
Afferent (sensory) root = Optic nerve CNII and tract
Efferent (motor) root = Oculomotor CNIII nerve
What are the two components of the pupillary light reflex?
Direct component = light in one eye, same pupil constricts
Consensual component = light in one eye, other pupil constricts