Book contents
- Frontmatter
- Contents
- List of Figures
- List of Tables
- Acknowledgements
- A note to the reader
- Part I Organization of the cranial nerves
- Part II-V Individual cranial nerves and functional considerations
- Part II Trigeminal, facial and hypoglossal nerves
- Part III Glossopharyngeal, vagus and accessory nerves
- Part IV Autonomic components of cranial nerves, taste and smell
- Part V Vision, eye movements, hearing and balance: optic, oculomotor, trochlear, abducens and vestibulocochlear nerves
- 20 The optic nerve (II)
- 21 The oculomotor (III), trochlear (IV) and abducens (VI) nerves
- 22 Visual reflexes: the control of eye movements; clinical testing of II, III, IV, VI
- 23 The vestibulocochlear nerve (VIII) and auditory and vestibular pathways
- Further reading
- Index
20 - The optic nerve (II)
Published online by Cambridge University Press: 25 August 2009
- Frontmatter
- Contents
- List of Figures
- List of Tables
- Acknowledgements
- A note to the reader
- Part I Organization of the cranial nerves
- Part II-V Individual cranial nerves and functional considerations
- Part II Trigeminal, facial and hypoglossal nerves
- Part III Glossopharyngeal, vagus and accessory nerves
- Part IV Autonomic components of cranial nerves, taste and smell
- Part V Vision, eye movements, hearing and balance: optic, oculomotor, trochlear, abducens and vestibulocochlear nerves
- 20 The optic nerve (II)
- 21 The oculomotor (III), trochlear (IV) and abducens (VI) nerves
- 22 Visual reflexes: the control of eye movements; clinical testing of II, III, IV, VI
- 23 The vestibulocochlear nerve (VIII) and auditory and vestibular pathways
- Further reading
- Index
Summary
Sight
Sight is dependent not only on a substantial portion of the cerebral cortex, but also upon six cranial nerves (II-VII). Perception is the function of the retina, optic nerve, tract, radiation and cortex. The oculomotor, trochlear and abducens nerves move the eye. Eyeball sensations such as pain, touch and pressure are mediated by the ophthalmic nerve, and the facial nerve innervates orbicularis oculi muscle. This Chapter deals with the optic pathway: eye movements and their control come later.
The optic nerve
The optic pathway transmits visual impulses from the retina to the brain. The optic nerve is the name given to the pathway between the eyeball and the optic chiasma. It is an artificial subdivision of the optic pathway. Like the olfactory nerve (Chapter 18), the optic nerve is not really a nerve. It is an outgrowth of the diencephalon (the thalamic structures). As in the olfactory system, the primary sensory neurons are bipolar and are confined to the sensitive epithelium (retina), the axons of secondary sensory neurons forming the optic nerve, chiasma and tract.
Visual pathways (Fig. 20.1)
Described from the eyeball back to the forebrain attachment.
Retina
Two layers: neural (next to vitreous) and pigment (next to choroid). Rods and cones in deepest parts of neural layer, with terminal processes of rods and cones in contact with pigment layer. Rods and cones synapse with bipolar cells (primary sensory neurons). Bipolar cells, confined to retina, synapse on ganglion cells. Axons of ganglion cells form optic nerve.
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- Information
- Cranial NervesFunctional Anatomy, pp. 115 - 120Publisher: Cambridge University PressPrint publication year: 2005