Cranial nerves
The cranial nerves, also called cranial nerves, are 12 pairs of nerves that arise directly from the brain or at the level of the brainstem to distribute through the foramina of the brain. the base of the skull in the head, neck, thorax and abdomen. The International Anatomical Nomenclature lists the nerve terminal as the cranial nerve, despite being atrophic in humans and closely related to the olfactory nerve.
Cranial nerves have an apparent origin which is the place where the nerve exits or enters the brain. The real origin is different according to the function they fulfill. Cranial nerve fibers with motor (efferent) function arise from cell groups deep in the brainstem (motor nuclei) and are homologous to the anterior horn cells of the spinal cord. Cranial nerve fibers with sensory or sensory (afferent) function have their cells of origin (first-order nuclei) outside the brainstem, usually in ganglia that are homologous to those of the dorsal spinal nerve root. Second-order sensory nuclei are located in the brain stem.
The nuclei from which the cranial nerves originate are located in a generalized region known as the tegmentum that runs along the brainstem.
- At the level of the mesencephalus (upper structure of the brain trunk) leave par III and IV
- At the level of the logencephalic bridge (average structure of the brain trunk) the pairs V, VI, VII and VIII are divided
- At the level of the spinal bulb (lower structure of the brain trunk) the pairs are IX, X, XI and XII.
Functional classification
According to its functional aspect
- Pairs I, II and VIII are dedicated to special sensitivities.
- Pairs III, IV and VI control eye movements, photomotor reflections and accommodation.
- The pairs XI and XII are pure motor nerves (XI for sternocleidomastoid and trapeze; and XII for the muscles of the tongue). However, the spinal roots of the accessory nerve (XI par) present sensitive fibers that emerge from the spinal cord, showing even a small node in the conjugation of the root fillets with the trunk of the spinal root of the nerve.
- The pairs V, VII, IX and X are mixed.
- Pairs III, VII, IX and X carry parasympathetic fibers.
Nerves
| Numbers | Names | Type of inervation | Origin Aparent | Nucleus | Function | Location |
|---|---|---|---|---|---|---|
| Classical classification | ||||||
| I | Olfactory nerve | Sensory | Direct it. | Previous olfactory core | Transmit the olfactory impulses | It is located in the olfactory foramenes of ethmoid scribed foil |
| II | Optical nerve | Sensory | Direct it. | Retina lymph node cells | Transmit visual information to the brain | It is located in the optical duct, which part of the middle cranial pit to previous. - |
| III | Oculomotor nerve (or Common Eye Motor) | Motor - Parasympathetic | Mesencéfalo Interpeduncular Fosa | Oculomotor core, Edinger-Westphal core | Inert the muscles: upper eyelid lifter, upper rectum, medial rectum, lower rectum and lower oblique, which collectively perform most eye movements; also inert the pupil's sphincter. | It is located in the sphenoidal cleft |
| IV | Troclear nerve (or Pathetic nerve) | Motor | Mesencéfalo | Core | Inerva por el segundo egundel obliqueo superior muscle, which depresses, rotates laterally (about the optical axis) and rotates internally the ocular balloon | It is located in the sphenoidal cleft |
| V | Trigeminon nerve | Sensitive - Motor | Bridge | Trigemino main sensory core, trigeminal spinal core, trigemino mesencephalic core, trigemino motor core | Perceive sensitive information of the face and inert the muscles of chewing (masetero and temporal) | It is located in the upper orbital fissure (offlasmic nerve - V1), round hole (maxillary nerve - V2) and oval hole (mandibular nerve - V3) |
| VI | Nervio abducens (or Nerve External Ocular Motor) | Motor | Later bridge margin | Nucleus Abducens | Inervate the right lateral muscle, which opens the eyeball | Located in the sphenoidal cleft |
| VII | Facial nerve | Sensory - Motor - Parasympathetic | Bridge (Photocerebelous clot) over the olive | Facial Nucleus, Solitary Core, Upper Salivar Core,[Lacrimonasal Nucleus] | It carries motor inervation to the muscles responsible for facial expression, posterior belly of the digestive muscle and the stapedio, receives the tasteful impulses of the previous two thirds of the tongue and provides secret-motor inervation to the salivales (with the exception of the paratoid) and the lagrimal gland | Climb the internal auditory channel to the facial channel and go out through the mastoid hole |
| VIII | Nerve vestibulococlear (or Nervio Auditivo o estatoacustico) | Sensory | Lateral to the VII pair (Photocerebelous clot) | vestibular core, cochlear core | Perception of sounds, rotation and gravity (essential for balance and movement). The vestibular branch carries impulses to coordinate balance and the cochlear arm carries auditory impulses | It is located in the internal auditory duct |
| IX | Gloosopharyngeal nerve | Sensory - Motor - Parasympathetic | Surco Retroolivar del Bulbo raquídeo | Nucleus ambiguus, lower salivar core, single core | It receives the tasteful impulses of the later third of the tongue, provides secret-motor inervation to the paralytic gland and motor inervation to the syropharyngeal muscle and the stylogloos muscle. It also transmits some information to the brain from the tons of the patellas. This is addressed to the opposite thalamus and some hypothalamus cores | Located in the jugular foramen |
| X | Vague nerve (or Neumogastric nerve) | Sensory - Motor - Parasympathetic | Surco Retroolivar de la medula oblongada o Bulbo raquídeo | Nucleus ambiguus, dorsal core vagal motor, lone core | It provides inervation to most of the laryngeal muscles and all the pharyngeal muscles, except in the pharyngeal style (inerated by the glyosopharyngeum); it carries parasympathetic fibers to the proximity of all the abdominal visceras located above the splenic flexure; and receives the sense of taste from the epiglotis. Control the muscles that help to articulate sounds in the soft palate. Symptoms of damage generate dysphagia, rapidpharyngeal insufficiency | It is located in the jugular foramen |
| XI | Spinal nerve (or Craneal Accessory or Brigade Accessory) | Motor | Cranial and spinal roots | Nucleus ambiguus, accessory spinal core | Controls sternocleidomastoid muscles and trapeze, overlaps with vague functions. Symptoms of damage include inability to shrink shoulders and weakness for cephalic movements | Located in the jugular foramen |
| XII | Hypogloss nerve | Motor | Bulbo raquíd | Hypogloss core | It provides motor inervation to the muscles of the tongue (except the palatogloss muscle, which is inervated by the vague nerve and the stylogloss muscle that is inervated by the glosopharynge nerve) and other lingual muscles. Important in swallowing (bolo formation) and sound articulation | It is located in the hypogloss nerve duct |
| Proposed nerves | ||||||
| 0 | Zero cranial | Sensitive | Olfactory triangle, medial olfactory circumvolution and terminalis foil | Recent research indicates that it may have a role in pheromone detection Joins the olfactory system in human embryos | ||
Yes
Embryology
The components of the sensory nervous system of the head are derived from the neural crest and from a population of embryonic cells that develops in close proximity, the cranial sensory placodes (the olfactory, lens, otic, trigeminal, epibranchial, and paratympanic). Cranial nerves form from the contribution of two populations of specialized embryonic cells, the cranial neural crest and the ectodermal placodes. The dual origin cranial nerves are summarized in the following table:
Contributions of neural crest cells and placodes to ganglia and cranial nerves
| Craneal nerve | Ganglio and Type | Origin of Neurons |
| CNI – Olfativo (cells in glia wrapped in the olfactory nerve) | Teleconcephalo/olfatoria; CCN in the Prosencephalo | |
| CNIII – Oculomotor (m) | Visceral Efferent, ciliar | CCN in the pro-sencephal-mesencephal union (low rate and previous mesencephale) |
| CNV – Trigeminal (mix) | Trigeminal, general aferente | CCN in the prosencephal-mesencephal union (from r2 to 1st AP), trigemino plaque |
| CNVII - Facial (mix) | - Senior, General and Special
-Sphenopatin, visceral efferent - Submandibular, visceral efferent | -CCN of the posterior brain (from r4 to the 2nd AP), 1st epibranchial placode
-1st epibranchial placode (geniculada) -NCC of the posterior brain (second AP) -Hindbrain NCCs (2nd PA) |
| CNVIII – Vestibulococlear (s) | - Acoustic: cochlear, special aferente; and Vestibular, special aferente | -Placoda ótico y CCN del rombencéfalo (de r4) |
| CNIX - Glosopharynge (mix) | - Senior, General and Special
-Inferior, petroso, aferente general y especial -Otico, visceral eferente | -CCN of the posterior brain (from r6 to 3rd PA)
-2nd epibranchial plate (petrosal) -CCN of the posterior brain (from r6 to third PA) |
| CNX - Vagus (mix) Upper laryngeal branch; and recurrent laryngeal branch | - Superior, general aferente
-Inferior: knot, general and special aferente -Vagal: parasympathetic, visceral efferent | -CCN of the posterior brain (from r7-r8 to 4o and 6o PA)
-CCN of the posterior brain (4o and 6o AP); 3o (nodoso) and 4o epibranchial placodes --CCN of the posterior brain (4th and 6th AP) |
| CNXI - Accessory (m) | No ganglion | Post-brain (from r7-r8 to AP 4); CCN (4o AP) |
Abbreviations: NC, cranial nerve; m, purely motor nerve; mix, mixed nerve (sensory and motor); CCN, neural crest cells; CN, neural crest; AP, pharyngeal (branchial) arch; r, rhombomere; s, purely sensory nerve. * There is no known accessory nerve ganglion. The cranial part of the accessory nerve sends occasional branches to the superior ganglion of the vagus nerve.