Page 531 - Fundamentals of anatomy physiology

Focus Cranial Nerves

Cranial nerves are PNS components that connect directly to the other nuclei or to processing centers in the cerebral or cerebellar
brain. The 12 pairs of cranial nerves are visible on the ventral cortex. In a similar way, the motor nuclei receive convergent in-
surface of the brain (Figure 14–19). Each has a name related to its puts from higher centers or from other nuclei along the
distribution or its function. brain stem.

The number assigned to a cranial nerve corresponds to the In this section, we classify cranial nerves as primarily sensory,
nerve’s position along the longitudinal axis of the brain, begin- special sensory, motor, or mixed (sensory and motor). In this
ning at the cerebrum. Roman numerals preceded by the letter N classification, sensory nerves carry somatic sensory information,
are usually used. (You may sometimes encounter these numerals including touch, pressure, vibration, temperature, or pain. Special
preceded by the letters CN.) sensory nerves carry the sensations of smell, sight, hearing, or
balance. Motor nerves are dominated by the axons of somatic
Each cranial nerve attaches to the brain near the associated motor neurons. Mixed nerves have a mixture of sensory and
sensory or motor nuclei. The sensory nuclei act as switching cen- motor fibers. This classification scheme is useful, but it is based
ters, with the postsynaptic neurons relaying the information to

Figure 14–19 Origins of the Cranial Nerves. An inferior view of the brain.

Olfactory bulb: termination Optic chiasm
of olfactory nerve (N I) Optic tract
Olfactory tract Mammillary body
Trochlear nerve (N IV)
Optic nerve (N II)
Infundibulum Trigeminal nerve (N V)
Abducens nerve (N VI)
Oculomotor nerve (N III)
Facial nerve (N VII)
Basilar artery
Pons Vestibulocochlear
nerve (N VIII)
Vertebral artery Glossopharyngeal
Medulla oblongata nerve (N IX)
Vagus nerve (N X)
Cerebellum Hypoglossal nerve (N XII)

Spinal cord Accessory nerve (N XI)

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