Cranial Nerves

Cranial Nerves

There are 12 pairs of cranial nerves, which arise from the underside of the brain (FIGURE 13-3). The first pair begins in the cerebrum and attaches to the fore-brain. The other 11 pairs begin in the brain stem. They all pass through the foramina of the skull. Most are mixed nerves, although the nerves for smell and vision are sensory nerves only. Sensory fibers in the cranial nerves have neuron cell bodies formed into ganglia. Motor neuron cell bodies are mostly located in the gray matter of the brain. The cranial nerves serve only structures of the head and neck, except the vagus nerve, which reaches the abdomen.

Cranial nerves are usually named based on the structures they serve or the functions they provide. They are numbered using Roman numerals, begin-ning with the most rostral nerves and ending with the most caudal. TABLE 13-1 lists and explains the cranial nerves in greater detail.

1. Explain the basic differences between afferent and efferent nerves.

2. Which of the cranial nerves only serve as sensory nerves?

3. Which pair of cranial nerves is the longest?