4th Trochlear N- This nucleus is cupped in the MLF beneath the inferior colliculus. The rootlets project dorsal and caudal to emerge in the roof plate (superior medullary vellum ) caudal to the inferior colliculus. The fourth nerve decussates at that point to loop ventrally around the midbrain to accompany the third and sixth N. Projects to the superior oblique M. only.

4th Trochlear N- This nucleus is cupped in the MLF beneath the inferior colliculus. The rootlets project dorsal and caudal to emerge in the roof plate (superior medullary vellum ) caudal to the inferior colliculus. The fourth nerve decussates at that point to loop ventrally around the midbrain to accompany the third and sixth N. Projects to the superior oblique M. only.
3rd Oculomotor N- The nucleus lies in the V form of the MLF beneath the superior colliculus. Motor to the remaining eye muscles (medial rectus, sup. & inf rectus, inf oblique and palpebri M..) The parasympathetic component is from Edinger-Westphal N that contains the preganglionic projection to the ciliary ganglion for constriction of the pupil accommodation (change thickness of lens & vergence).
2nd Optic N- Ganglion cells of the retina project to the lateral geniculate Nuc. of the thalamus, to the superior colliculus and to the supraoptic nuc in hyopothalamus.
1st Olfactory N- Receptor cells of the nasal epithelium project axons through the cribiform plate to the olfactory bulb and synapse in olfactory glomeruli. These are the only sensory cells in the PNS with an axon.

2nd Optic N- Ganglion cells of the retina project to the lateral geniculate Nuc. of the thalamus, to the superior colliculus and to the supraoptic nuc in hyopothalamus.