Except for the olfactory and optic nerves, which evolved from the outward projection of the ventricular wall during the embryonic period, all other nerves are similar to the spinal nerves, but have their own characteristics, i.e., the brain nerves can be divided into: sensory nerves; motor nerves; and mixed nerves. The sensory nerves and optic nerves are connected to the telencephalon and mesencephalon respectively, while the rest are connected to the brainstem, and the paranerves still have fibers from the superior cervical medulla.
In addition to the four fiber components of somatic afferent, penetrating and visceral afferent and penetrating, there are also three fiber components of special somatic afferent and special visceral afferent and transmitting.
1. Olfactory nerve
The olfactory impulses are transmitted by the central protrusions of the olfactory cells in the mucosa of the superior turbinate and upper nasal septum, which gather into 15-20 olfactory filaments and cross the sieve plate into the anterior cranial fossa and connect to the olfactory bulb on the ventral side of the brain.
2. Optic nerve
It starts from the retina of the eye and enters the middle fossa of the skull through the optic nerve canal from the orbit and continues at the optic cross.
3.Actinic nerve
It is a motor nerve that leaves the brain ventrally from the midbrain, passes through the dura mater into the lateral wall of the cavernous sinus, and continues forward through the superior orbital fissure into the orbit. The former innervates most of the extraocular muscles, while the latter is the parasympathetic preganglionic fibers of the motoneurone nerve to the ciliary ganglion in the orbit, and the postganglionic fibers initiated by the ganglion cells to the eye, innervating the pupillary sphincter and ciliary muscles.
4.Sliding nerve
The somatic motor nerve exits the brain at the dorsal anterior medullary sail of the midbrain, passes forward around the cerebral peduncle into the lateral wall of the cavernous sinus, continues anteriorly below the motoneurotic nerve, passes through the superior orbital fissure above the motoneurotic nerve and enters the orbit, innervating the superior oblique muscle. The carotid nerve and the motor nerve also contain proprioceptive fibers.
5.Trigeminal nerve
It is the largest nerve in the brain and is the main sensory nerve of the head and face, as well as the motor nerve of the masticatory muscles. Most of the somatosensory fibers originate from the trigeminal ganglion. The trigeminal ganglion is located at the tip of the trigeminal nerve at the tip of the temporal bone, and is divided into three major branches by the anterior and lateral edges of the ganglion: (1) ophthalmic nerve: it is a sensory nerve, the smallest oh, penetrating forward into the lateral wall of the cavernous sinus, living below the pudendal nerve, and then entering the orbit through the superior orbital fissure. (2) Maxillary nerve: larger, also a sensory nerve, penetrates forward into the lower part of the lateral wall of the cavernous sinus, followed by horizontal forward, exits the cranial cavity into the pterygopalatine fossa through the round hole, then enters the orbit by the inferior orbital fissure, and continues as the infraorbital nerve. (3) Mandibular nerve: the largest, a mixed nerve, through the foramen ovale to the inferior temporal fossa.
6.Spreading nerve
It is a somatic motor nerve that leaves the brain on both sides of the median line between the medulla oblongata, passes through the dura mater lateral to the saddle and enters the cavernous sinus, travels forward out of the cavernous sinus in the lateral line of the internal carotid artery, and then enters the orbit through the medial end of the superior orbital fissure to the external rectus muscle.
7.Facial nerve
It is a mixed nerve, attached to the brain at the lateral part of the pontine sulcus of the medulla oblongata, enters the internal auditory canal through the inner ear door, crosses the facial nerve canal curved within the bone of the temporal bone rock, and finally leaves the skull through the stem mammary foramen. The facial nerve contains: (1) special visceral efferent fibers mainly innervating the expression muscles; (2) general visceral efferent fibers; (3) special visceral afferent fibers; (4) general visceral afferent fibers; (5) general somatosensory fibers.
8.Local auditory nerve
It consists of the vestibular nerve, which conducts positional balance sensory impulses, and the sural nerve, which conducts auditory impulses. The vestibular ganglion is located at the base of the inner ear canal. The cochlear ganglion is located in the spiral canal of the inner cochlea. The two nerves begin at the base of the internal auditory canal and enter the brain via the lateral end of the medulla cerebralis bridge and the lateral aspect of the facial nerve.
9.Glottopharyngeal nerve
It is a mixed nerve, formed by a collection of many filaments attached to the lateral aspect of the medulla oblongata, and exits the cranial cavity through the jugular foramen. The nerve contains: (1) special visceral efferent fibers innervating the pharyngeal and laryngeal muscles; (2) general visceral efferent fibers distributed in the parotid gland; (3) special visceral afferent fibers (taste); (4) general visceral afferent fibers; (5) general somatosensory fibers distributed in the ear nail and part of the skin of the external auditory canal.
10.Vagus nerve
It is a mixed nerve, which is assembled into a trunk below the glossopharyngeal nerve by many root filaments attached to the medulla oblongata. It passes through the cranial cavity of the jugular foramen. The nerve contains: (1) special visceral efferent fibers innervating the pharyngeal constrictor and cervicopharyngeal muscles; (2) general visceral efferent fibers distributed in the parotid gland; (3) special visceral afferent fibers (taste); (4) general visceral afferent fibers; (5) general somatosensory fibers distributed in the ear nail and part of the skin of the external auditory canal.
11.Parasympathetic nerve
It is a special visceral motor nerve, composed of medullary roots and spinal roots.
12.Sublingual nerve
It is a somatic motor nerve that leaves the brain from the lateral sulcus of the medulla oblongata and exits the cranial cavity via the sublingual nerve canal. The hypoglossal nerve innervates the lingual muscle.