The human nervous system. Sky blue is PNS; yellow is CNS.
Nerves (yellow) in the arm
Autonomic nervous system innervation, showing the parasympathetic (craniosacral) systems in blue.
3D Medical Animation still shot of Lumbosacral Plexus
Cross-section of a nerve
Micrograph demonstrating perineural invasion of prostate cancer. H&E stain.

A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system.

- Nerve

The PNS consists of the nerves and ganglia outside the brain and spinal cord.

- Peripheral nervous system

Nerve fibres of the parasympathetic nervous system arise from the central nervous system.

- Parasympathetic nervous system

The parasympathetic nerves are autonomic or visceral branches of the peripheral nervous system (PNS).

- Parasympathetic nervous system

The connection between CNS and organs allows the system to be in two different functional states: sympathetic and parasympathetic.

- Peripheral nervous system

The autonomic nervous system is further subdivided into the sympathetic and the parasympathetic nervous systems.

- Nerve
The human nervous system. Sky blue is PNS; yellow is CNS.

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Overall

Left View of the human brain from below, showing origins of cranial nerves. Right Juxtaposed skull base with foramina in which many nerves exit the skull.

Cranial nerves

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Left View of the human brain from below, showing origins of cranial nerves. Right Juxtaposed skull base with foramina in which many nerves exit the skull.
The oculomotor (III), troclear (IV) and abducens (VI) nerves supply the muscle of the eye. Damage will affect the movement of the eye in various ways, shown here.
The facial nerve (VII) supplies the muscles of facial expression. Damage to the nerve causes a lack of muscle tone on the affected side, as can be seen on the right side of the face here.
A damaged glossopharyngeal nerve (IX) may cause the uvula to deviate to the affected side.
The cranial nerves in the horse.
Ventral view of a sheep's brain. The exits of the various cranial nerves are marked with red.

Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), of which there are conventionally considered twelve pairs.

The cranial nerves are considered components of the peripheral nervous system (PNS), although on a structural level the olfactory (I), optic (II), and trigeminal (V) nerves are more accurately considered part of the central nervous system (CNS).

Additional ganglia for nerves with parasympathetic function exist, and include the ciliary ganglion of the oculomotor nerve (III), the pterygopalatine ganglion of the maxillary nerve (V2), the submandibular ganglion of the lingual nerve, a branch of the facial nerve (VII), and the otic ganglion of the glossopharyngeal nerve (IX).