Cranial Nerves and Chemical Senses

Abstract

Twelve pairs of cranial nerves are peripheral nerves of the brain (see Fig. 14.1). The olfactory and optic nerves are nerves of the cerebrum (telencephalon). The other 10 pairs are nerves of the brainstem (and in one case, partially of the cervical spinal cord). They supply structures of the head and neck and, in the case of the vagus nerve, structures of the trunk. Some cranial nerves contain almost exclusively afferent fibers, others almost exclusively efferent fibers, and a third group contains substantial proportions of both affterent and efferent fibers (see Table 14.1). The afferent fibers arise with one exception, those that mediate unconscious proprioception, from cell bodies located in peripheral ganglia; their central processes enter the brainstem and end in sensory nuclei of termination (see Fig. 14.2). Efferent fibers arise from cell bodies located in brainstem motor nuclei (see Fig. 14.3).