CRANIAL NERVES
Cranial nerves
The motor fibers or efferent cranial nerves arise from groups of neurons in the brain that are their nuclei of origin.
They are connected with the cortex of the brain corticonuclear the fibers that originate from neurons of the motor areas of the cortex, falling mainly in the genu of the internal capsule to the brainstem.
The sensory or afferent cranial nerves originate from neurons outside the brain, or grouped to form ganglia located in peripheral organs.
The nuclei that give rise to ten of the twelve cranial nerves are located in vertical columns in the brain stem and correspond to the gray matter of the spinal cord.
According to the functional component, cranial nerves can be classified into motor, sensory and mixed.
Engines (pure) are those that move the eyes, the tongue and accessory latero-posterior muscles of the neck. They are:
III - Oculomotor Nerve
IV - Trochlear Nerve
VI - Abducens Nerve
XI - Accessory Nerve
XII - Hypoglossal Nerve
Psychics (pure) are used to sense organs and are therefore called sensory, not just sensitive, that do not relate to the overall sensitivity (pain, temperature and touch). The sense is:
I - Olfactory Nerve
II - Optic Nerve
VIII - Nerve Vestibulocochlear
The mixed (motor and sensory) are four in number:
V - Trigeminal
VII - Facial Nerve
IX - Glossopharyngeal Nerve
X - Vagus Nerve
Five of them still have vegetative fibers, constituting part crânica peripheral autonomic system. Are:
III - Oculomotor Nerve
VII - Facial Nerve
IX - Glossopharyngeal Nerve
X - Vagus Nerve
XI - Accessory Nerve
I. Olfactory Nerve
The olfactory nerve fibers are distributed in a special area of the nasal mucosa which is called the olfactory mucosa. Because of the existence of large quantities of individualized issues that cross the sieve separately ethmoid, that is called the olfactory nerves, and not simply the olfactory nerve (right and left).
It is a purely sensory nerve, the fibers conduct impulses olfactory and were classified as special visceral afferent. More information about the olfactory nerve can be found at Telencephalon (Rhinic).
II. Optic Nerve
It consists of a thick bundle of nerve fibers that originate in the retina, emerge near the posterior pole of each eyeball, penetrating the brain through the optic canal. Each optic nerve joins with the opposite side, forming the optic chiasm, where there is partial crossing of fibers, which continue in the optic tract to the lateral geniculate body. The optic nerve is a purely sensory nerve, the fibers conduct impulses visual, being classified as special somatic afferent.
III. Oculomotor Nerve
IV. Trochlear Nerve
VI. Abducens Nerve
Are motor nerves that penetrate the orbit by the superior orbital fissure, distributing to extrinsic ocular muscles, which are: levator palpebrae superioris, superior rectus, inferior rectus, medial rectus, lateral rectus, superior oblique, inferior oblique. All these muscles are innervated by the oculomotor, except the lateral rectus and superior oblique, respectively innervated by the abducens and trochlear nerves. The fibers that innervate the extrinsic eye muscles are classified as somatic efferent.
The oculomotor nerve arises in the groove of the medial cerebral peduncle, the trochlear nerve just below the inferior colliculus, and the abducens nerve in the inferior pontine sulcus, near the midline.
The three nerves at hand approach, still inside the skull, to cross the superior orbital fissure and reach the orbital cavity, going to distribute the extrinsic muscles of the eye.
The oculomotor nerve fibers leads still vegetative, going to the intrinsic muscles of the eye, which moves the lens and iris.
V. Trigeminal Nerve
The trigeminal nerve is a mixed nerve, the sensory component is considerably larger. Has a sensory root and a motor. The sensory root is formed by extensions of the central sensory neurons, located in the ganglion trigemial, located in the trigeminal dig on the petrous temporal bone. The peripheral extensions of sensory neurons of trigeminal ganglia form distal to the ganglion, the three branches of the trigeminal nerve: ophthalmic nerve, maxillary nerve and mandibular nerve, responsible for general somatic sensibility of much of the head, through fiber to be classified as afferent general somatic. The motor root of trigeminal nerve consists of fibers attached to the mandibular nerve, distributed to the masticatory muscles. The medical condition most often seen in relation to trigeminal neuralgia is, manifested by painful crises very intense in the territory of one of the branches of the nerve.
1. Ophthalmic nerve: passes through the superior orbital fissure (along with the III, IV, VI cranial nerves and the ophthalmic vein) to reach the orbit and provides three terminal branches, which are nerves nasociliary, frontal and lacrimal glands.
The ophthalmic nerve is responsible for the sensitivity of the orbital cavity and its contents, while the optic nerve is sensory (vision).
2. Maxillary nerve: is the second branch of the trigeminal nerve. He crosses the pterygopalatine fossa like an aerial cable to enter into the inferior orbital fissure and into the orbital cavity, when it changes its name to infra-orbital nerve.
The infra-orbital nerve remains the same forward direction passing the floor of the orbit, passing successively by the groove, channel, and infra-orbital foramen and through the latter is exteriorized to innervate the soft tissues located between the lower eyelid (No lower eyelids) nose (n.nasal) and upper lip (no upper lip).
The infraorbital nerve (terminal branch of maxillary nerve) provides as collateral branches of the superior alveolar nerve middle and anterior superior alveolar nerve, which are directed downward.
Near the apex of the roots of upper teeth, the three superior alveolar nerves send branches that anastomose abundantly as to constitute the superior dental plexus.
3. Mandibular nerve: the third branch of the trigeminal nerve. He travels through the skull through the foramen ovale and branches just below this a real bouquet, and the two main branches are the lingual and inferior alveolar nerve.
The lingual nerve goes to the language, giving overall sensitivity to their previous two thirds.
The inferior alveolar nerve enters the mandibular foramen and runs into the bone canal of the mandible to the central incisor tooth.
Approximately at the time of the second premolar, the inferior alveolar nerve sends a collateral branch, which is the mental nerve (mental nerve), which emerges through the foramen of the same name, to provide general sensitivity to the soft parts of the chin.
Within the mandibular canal, the inferior alveolar nerve branches, but its branches anastomose to form the wildly inferior dental plexus, which leave the inferior dental branches going to the lower teeth.
The motor part of the mandibular nerve innervates the masticatory muscles (temporal, masseter and medial and lateral pterygoid), with nerves that has the same name of the muscles.
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VII. Facial nerve
It is also a mixed nerve, with a motor root and other sensory gustatory. He emerges from the groove bulbopontine through a motor root, the facial nerve itself, and a visceral sensory root and the nerve through. Along with the vestibulocochlear nerve, the two components of the facial nerve penetrate the internal auditory canal, within which the intermediate nerve loses its individuality, forming thus a unique nerve trunk that penetrates into the facial canal.
The motor root is represented by the facial nerve itself, while the sensory nerve is called intermediate.
Both have apparent origin in the inferior pontine sulcus and are directed parallel to the internal acoustic meatus where they penetrate with the vestibulocochlear nerve.
Within the internal auditory canal, the two nerves (facial and intermediate) penetrate a channel dug itself in the petrous temporal bone, which is the facial canal.
The motor fibers cross the parotid gland reaching the surface, where they give two initial branches: the temporal facial and cervico facial, which ramify in range to innervate all muscles of cutaneous head and neck.
Some motor fibers go to the style-hyoid muscle and the posterior belly of digastric.
The fiber sensory (gustatory), follow a branch of the facial nerve which is the chorda tympani, which will join the lingual nerve (mandibular third branch of trigeminal), taking as a vector to deliver on the anterior two thirds of language.
The facial nerve has also vegetative fibers (parasympathetic) that use the intermediate nerve and then followed by the greater petrosal nerve or the chorda tympani (both branches of the facial nerve) to innervate the lacrimal glands, nasal and salivary (submandibular and sublingual gland) .
In summary, the facial nerve gives motor innervation to all muscles of cutaneous head and neck (style-hyoid muscle and posterior belly of digastric).
VIII. Vestibulocochlear nerve
Costituído by two groups of fibers that form perfectly individualized, respectively, the vestibular and cochlear nerves. It is a purely sensory nerve, which enters the bridge in the lateral portion of the groove bulbopontine between the emergence of pair VII and the flocculus of the cerebellum. Occupies along with the facial nerves and through the internal auditory canal in the petrous portion of temporal bone.
The vestibular portion is formed by fibers that originate from the vestibular ganglion sensory neurons, which conduct nerve impulses related to balance.
The cochlear part consists of fibers that originate from the sensory neurons of the spiral ganglion and conducting nerve impulses related to hearing.
The fibers of the vestibulocochlear nerve are classified as special somatic afferent.
IX. Glossopharyngeal Nerve
It is a mixed nerve that emerges from the posterior lateral sulcus of the medulla in the form of root filaments, arranged in vertical line. These strands come together to form the trunk of the glossopharyngeal nerve, which exits the skull through the jugular foramen. In its path, through the jugular foramen, the nerve contains two nodes, top and bottom, formed by sensory neurons. Upon exiting the skull, the glossopharyngeal nerve is downward path, branching off at the root of the tongue and pharynx. Of these, the most important is represented by the general visceral afferent fibers responsible for the overall sensitivity of the posterior third of the tongue, pharynx, uvula, tonsils, auditory tube, and sinus and carotid body. Also worth mentioning the general visceral efferent fibers belonging to the parasympathetic division of the autonomic nervous system and terminating at the optic ganglion. This ganglion, leaving nerve fibers nerve auriculotemporal ranging innervate the parotid gland.
XI. Accessory Nerve
Formed by a cranial and a spinal root. The root cord is formed by filaments that emerge from one side of five or six first cervical spinal segments, forming a trunk that penetrates the skull through the foramen magnum. In this trunk unite cranial root filaments that emerge from the posterior lateral sulcus of the medulla.
The trunk divides into an internal and an external branch. The intern joins the vagus and distribute with it, and the external innervates the sternocleidomastoid and trapezius muscles.
The fibers originated from the cranial root that join the vagus are:
Special visceral efferent fibers, which innervate the muscles of the larynx;
General visceral efferent fibers, which innervate thoracic viscera.
XII. Hypoglossal Nerve
Primarily motor nerve. Emerges from the anterior lateral sulcus of the medulla in the form of root filaments that unite to form the nerve trunk. This emerges from the skull through the hypoglossal canal, and addresses the intrinsic and extrinsic muscles of the tongue (is related to the same motor). Their somatic efferent fibers are considered.
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