• Optic Nerve is connected to Lateral Geniculate Nuclei and Superior Culiculi.
➩ CN I and II are connected to telencephalon.
➩ CN III and IV are connected to Midbrain
➩ CN V, VI, VII,VIII are connected to pons
➩ CN IX, X, XII are connected to Medulla.
➩ XI connected to spinal cord.
➢ III, IV, VI, XI, XII are motor nerves
➢ V, VII, IX and X are mixed nerves.
CN I : Limbic system
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• 2 Pathways:
1. Afferent- by sensation. Optic nerve to LGB, relay to Mid Brain (Superior Colliculus). Deep to Superior Colliculus is Pretectal nucleus ( Fibers relay to the nucleus). From the nucleus, to Edinger Westphal Nucleus.
2. Efferent: Respond to Sensation (is by CN#3): From Edinger Westphal Nucleus to CN#3 and supplies the sphincter pupilae. Efferent from Edinger Westphal foes to CN 3, and relays to Ciliary Ganglia (till this point, it is pre-ganglionic, from Ciliary ganglia it becomes the post Ganglionic and relays to Sphincter Nuclei).
-Both Afferent and Efferent pathways happens at the same time.
* Any parasympathetic system, before it reaches the target has to relay on a Ganglia.
Ciliary Ganglia is concerned with pupillary light and accommodation reflex.
➣Sensations from the optic nerve are carried to LGB. This pathway does not go to Occipital cortex
➣ From LGB, it reaches the Pretectal Nucleus. From pretectal nucleus, it goes to Edinger Weslphal nucleus.
( from this moment on, it is no longer sensory). From Edinger weslphal nucleus the fibers joins the CN#3. These fibers will be the efferent fibers. These fibers relay into target zone which is pupils
➣ Pupils have two types of muscles:
• Sphincter muscle
➣ Pupillary light reflex goes all the way to sphincter pupillary muscle.
➣ Before the fibers reaches Sphincter nucleus, as these fibers are parasympathetic, it has to be relayed on ganglia.
➣ The ganglia associated with the pupillary reflex is ciliary ganglia.
➣ Till that ganglia, the efferent fibers are called pre-ganglionic fibers which goes through occulomoter nerve. After the ganglia (post ganglionic), the fibers joins with ophthalmic division of trigemeninal nerve and reaches sphincter pupil
➣ CN III is associated with pre-ganglionic path and CN V associated with post-ganglionic.