Some cranial nerves

1.1 Cranial nerves and their functions (Table 1.1) Cranial nerves arise from the brain as twelve pairs. They pass through or into the cranial bones (thus cranial nerves) and are numbered I to XII roughly in order from top (rostral) to bottom (caudal). Their functions are those of the head: some are concerned with awareness of, and communication with, the environment; and some are concerned with sustenance, the gut tube and movements associated with it.

1.2 Cranial nerves and spinal nerves are differently constituted Cranial nerves are not equivalent to spinal nerves.All spinal nerves have similar functions and carry similar types of nerve fibre (motor, sensory, autonomic, etc.). This is not so for cranial nerves:

• Some cranial nerves contain only sensory fibres, some contain

only motor fibres, and some contain both.

• Some cranial nerves convey parasympathetic fibres, some convey

taste fibres, some convey both, and some neither.

Cranial nerves exhibit great variety and functional specialization. This is evident in Table 1.1 which summarizes their numbers, names and main functions. Learn this table without further ado, and make sure that you can use names and numbersTable 1.1. Synopsis of cranial nerves.