Cranial Nerves

The peripheral nervous system (PNS)

The remaining nerves existing the CNS

The trigeminal nerve branches

The trigeminal nerve divides into three branches at the semilunar ganglion (Gasserian Ganglion). Meckel's cavity: V1: ophthalmic division - sensory/afferent V2: maxillary division - sensory/afferent V3: mandibular division - both sensory & motor, afferent/efferent.

The pons or pontine area

The ventral side of the brainstem which is an area where several neuronal processes crossover from the right to the left side of the brain

Cranial nerves

There are 12 sets of cranial nerves. they provide innervations to the left and right sides of the body. the nerves are designated by Roman numeral. they carry motor sensory neurons, somatic and autonomic neurons

Ophthalmic division branches

There are three branches: Lacrimal Nerve: it innervates the lacrimal gland for tear production and the skin of the upper eyelid. Frontal nerve: Passes above the eye and divides into: a supraorbital nerve and a supratrochlear nerve. Nasociliary Nerve: supplies the inside of the Nose and also the skin on the side of the nose

Brainstem functions

They include the so-called lower or basic functions of the brain most of which are life-sustaining. Regulation of hartbeat and respiration, regulation of digestion and excretion, mastication and swallowing centers and pain perception and regulation.

II optic nerve

Transmits sight from the retina of the eye to the brain and thus functions as an afferent sensory nerve. It enters the skull through the optic canal of the sphenoid bone on the way to the retina

Maxillary division (infraorbital nerve)

Exits the skull through the infraorbital foramen; before it exits two branches are given off: 1. Middle superior Alveolar nerve 2. Anterior superior alveolar nerve

Cranial Nerve VIII (2 major portions)

1. Cochlea - serves the function of hearing & is supplied by the cochlear part of the vestibulocochlear nerve. 2. Semicircular canals - serves the function of balance and is supplied by the vestibular portion of the semicircular canals.

Three types of dental plexus nerves

1. Dental nerves enter through apical foramen, pulpal innervation 2. Interdental nerves innervate to the PDL, interdental papillae and Buccal gingiva 3. Interradicular nerve which innervates to the PDL of adjacent roots.

Cranial Nerve VII Branches in the face

1. Posterior auricular nerve 2. Nerve to digastric & Stylohyoid muscles 3. Temporal Branches 4. Zygomatic branches 5. Buccal branches 6. Marginal mandibular nerve 7. Cervical branch

Cranial Nerve VI

Abducens, efferent to one of the muscles that moves the eyeball. it runs through the sinus, close to the internal carotid artery, and is often the first nerve affected by infections of the sinus. Origin: it emerges as the roots from the brain stem b/w the pons & the medulla oblongata.

Cranial Nerve XI

Accessory Nerve. Efferent = muscles of neck, soft palate & pharynx. Passes through the skull by way of the jugular foramen, b/w the occipital and temporal bones.

The decussation of pyramids

Another area of crossover

Mandibular Division (V3): Buccal Nerve (Buccinator)

Branches from the anterior division of the inferior alveolar nerve and emerges through the buccinator muscle. Sensory innervation to the Buccal gingiva of the mandibular molars as well as the mucosa and skin of the cheek.

Anterior superior alveolar nerve (ASA)

Branches within the infraorbital canal, exits the IO canal, provides sensory innervation to bone and labial gingiva of the maxillary central and lateral incisors and canines, maxillary sinus.

Maxillary division (V2)

Branches: within the cranium (middle meningeal nerve). Pterygopalatine fossa (NP, GP, PSA - significant to dental anesthesia). Infraorbital canal (MSA, ASA). On the face: inferior palpebral (behind the orbicularis oculi, for lower eye lid), external nasal, superior labial.

Cranial Nerve XII

Hypoglossal. Efferent - tongue muscles movement. Exits the skull through the hypoglossal canal in the occipital bone.

Cranial Nerve VII

Facial Nerve, both efferent & afferent. Efferent = Muscles of facial expression, other cranial muscles, lacrimal, sublingual, submandibular and minor glands (Parasympathetic). Afferent = skin around ear and tongue (taste sensation). Exits through the internal acoustic meatus, which leads to the facial canal inside the temporal bone and exits through the stylomastoid foramen behind the ear & spreads across the face. Supply = the motor fibers provide somatic motor innervation to the muscles of the face, scalp, and auricle, the buccinators, platysma, stapedius, Stylohyoid, and the posterior belly of the digastric.

Cranial Nerve IX

Glossopharyngeal Nerve, both. efferent = stylopharyngeus muscle & parotid gland (Parasympathetic) Afferent - skin around ear & tongue (taste & general sensation)

Nervous system

Important to dentistry because it allows for the function of: muscles, TMJ, glands of the head and neck, pain management that involves administration of LA and related nervous system disorders of the head and neck that need to be known by the hygienist

Maxillary division: posterior superior alveolar nerve (PSA)

Innervates the Maxillary molars (all except the mesial Buccal root of the Max 1st molar), Buccal gingiva in the area, and Max sinus. The PSA descendens through the pterygopalatine fossa to the posterior surface of the maxilla. Most often has two trunks but occasionally one trunk is present.

Mandibular Division (V3): Auriculotemporal Nerve

Innervates the TMJ

Mandibular Division (V3): Lingual Nerve

Innervates the tongue, the floor of the mouth, and the lingual gingiva of the entire arch. Runs b/w the medial pterygoid muscle and the mandible. Afferent (sensory)

Middle superior alveolar nerve (MSA)

It branches with the infraorbital canal, exits the IO canal, not present in 68% (b/w 50-72%) of the population. Provides sensory innervation to the maxillary premolars, sometimes the mesiobuccal root of the maxillary first molar, periodontal tissues, Buccal gingival in the area of the maxillary sinus. When missing the MSA, you anesthetize the ASA.

Sensory root of the trigeminal nerve

It has three divisions: The ophthalmic - exits the superior orbital Fissure. The maxillary - exits the foramen rotundum. The mandibular - exits the foramen ovale. The motor nerve accompanies the sensory root of the mandibular nerve and exits the foramen ovale

The brainstem (CNS)

It is composed of many neuronal processes or pathways that travel up to the cerebrum and cerebellum and down to the spinal cord. It also contains many regulatory nuclei and 12 pairs of nerves called the cranial nerves

IV trochlear nerve

It is the only cranial nerve that emerges from the dorsal surface of the brain. Efferent or motor for one eye muscle as well as proprioception. Similar to the oculomotor nerve but without the parasympathetic fibers. It exits through the skull via the superior orbital Fissure of the sphenoid bone

Ophthalmic division (V1)

It's the first division, the smallest, sensory/afferent, it enters the eye through the superior orbital fissure, it provides sensation to the eye, lacrimal glands, skin of the eyelids, forehead and the nose. has three branches and none lead to the oral cavity

Mandibular Division (V3)

Largest Division of the 3, Mixed: sensory & motor. exits the skull through the foramen ovale. 4 branches: Buccal, lingual, inferior alveolar nerve, auriculotemporal nerve.

Mandibular Division (V3) Inferior Alveolar Nerve

Largest branch of V3, Enters the mandible through the mandibular foramen, and continues in the mandibular canal. Gives off branches to both the mandibular molars and premolars. At the mental foramen, it divides into 2 terminal branches: 1. Mental Nerve (innervates chin & lower lip & exits through the mental foramen) 2. Incisive Nerve (forms the inferior dental plexus, innervates pulpal tissues of premolars, canines and incisors and the mandibular anterior teeth & labial gingiva)

III oculomotor nerve

Main source of innervation of the extra ocular muscles. It also contains parasympathetic fibers that relay in the ciliary ganglion. It serves as an Efferent or motor nerve and exits through the skull via the superior orbital Fissure Of the sphenoid bone

Efferent Nerves

Motor nerves that carry information away from the brain or spinal cord to the periphery of the body in response to the afferent nerves

Somatic nervous system (SNS)

Muscular system and X ternal sensory receptors

Maxillary division (pterygopalatine nerve)

Nasopalatine nerve, passes across the roof of the nasal cavity lies between the mucous membrane and the periosteum of the nasal septum. It passes through the incisive foramen and innervates the palatal mucus and the lingual gingiva in the area of the maxillary incisors

The 12 cranial nerves

Olfactory, optic, oculomotor, Trochlear, trigeminal, abducens, facial, vestibuloacoustic/auditory, glossopharyngeal, Vagus, spinal accessory, hypoglossal.

Two trunks of maxillary division (V2)

One branch remains external to the bone provides sensory innervation to the Buccal gingiva in the maxillary molar area and adjacent facial tissues. The second branch enter through the PSA canal into the maxilla provides sensory innervation to the alveoli, periodontal ligament, and pulpal tissues of the maxillary third, second and first molars (exception sometimes being the mesial Buccal root of the first molar in about 30% of the population will be innervated by the MSA).

The motor rule of the trigeminal nerve

Originate within the pons & medulla oblongata. Separates from the sensory root (V3) within the cranium. It passes down towards the foramen ovale along with but separate from the (V3) sensory root. After leaving the skull The motor root unites with the sensory root of the mandibular division (V3) to form a single nerve trunk. The Motor root includes the muscles of mastication: the masseter, temporalis, medial pterygoid as well as the mylohyoid, the anterior belly of the digastric, tensor tympani, and tensor veli palatini

Lingual Nerve

Provides general sensation and taste for anterior 2/3 of the tongue, sensory innervation to the soft tissues on the floor of the mouth and lingual gingiva.

Maxillary division (descending Palitine nerve)

Runs straight down from the Pterygopalatine ganglion, and branches into the Greater palatine nerve (innervates the palatal mucosa and the lingual gingiva of the maxillary posterior teeth in canines) and the lesser Palatine nerves (innervates the soft palate and the tonsils)

Afferent nerves

Sensory nerves that carry information such as taste pain and proprioception from the periphery of the body to the brain or spinal cord

Mandibular Division Innervation (V3)

Sensory root: Skin (Temporal region, auricula, external auditory meatus, cheek, lower lip, chin), Mucous Membrane (cheek, anterior 2/3 of tongue), mandibular teeth, perio tissues, bone of the mandible, TMJ, Parotid gland. Motor Root: Muscles of mastication (temporalis, masseter, medial pterygoid), mylohyoid, anterior belly of the digastric muscle, tensor tympani, tensor veli palatini

Maxillary division (V2)

Sensory/Afferent (only). It exits the skull through the foramen rotundum. Has 5 nerve branches: 1. Zygomatic 2. Infraorbital 3. Posterior superior alveolar 4. Pterygopalatine 5. Descending palatine

Maxillary division innervation (V2)

Skin: The middle portion of the face, the lower eyelid, the side of the nose, and the upper lip. Mucous membrane: The nasopharynx, the maxillary sinus, hard/soft palate and tonsil. Maxillary teeth and periodontal tissues

2 Portions of Cranial Nerve VII

Superficial: originates in the ventral brainstem in the facial motor nucleus, sending processes out to innervate the muscles of the face. Deep: originates in the brainstem and pass through the superior orbital fissue w/ cranial nerve VI, to the nasal mucosa & lacrimal gland, innervating glands (not muscles).

The dental plexus

Superior dental plexus are small nerves going to the tips of the roots of the teeth and are composed of smaller nerve fibers from the PSA, MSA and ASA.

Maxillary division (zygomatic nerve)

Supplies the skin and side of the forehead and the skin of the cheek. It enters the eye through the inferior orbital Fissure.

Frontal nerve division

Supraorbital nerve supplies the skin of the forehead, scalp and upper eyelid. the supratrochlear nerve supplies the skin of the forehead & upper eyelids

Autonomic nervous system (ANS)

Sympathetic fight or flight and parasympathetic rest or digest

Inferior Dental Plexus

Terminal branches of the inferior alveolar nerve in the mandible.

Two main divisions of the nervous system

The (CNS) the central nervous system and the (PNS) the peripheral nervous system. Then there are afferent nervous system and efferent nervous system and finally somatic nervous system (SNS) and autonomic nervous system (ANS)

The central nervous system (CNS)

The brain and spinal cord portions

V Trigeminal nerve

The largest of the cranial nerves and is both a efferent and afferent. Efferent innervation for the muscles of mastication as well as cranial muscles for the face, nose, scalp and Mouth. Afferent component for teeth, tongue and oral cavity as well as most of the skin of the face and head. The trigeminal nerve is the most important cranial nerve to dental professionals because it innervates many relevant tissues of the head and neck.

Cranial Nerve X

Vagus Nerve, both. Afferent - skin around ears & epiglottis (taste sensation). Efferent - muscles of the soft palate, pharynx, and larynx, and thorax abdominal organs (parasympathetic)

Cranial Nerve VIII

Vestibulocochlear Nerve or auditory nerve, afferent nerve for hearing and balance. the vestibulocochlear nerve (VIII cranial nerve) arises alongside the facial nerve on the lateral side of the brain b/w the pons and medulla oblongata. Enters through the cranial cavity through the internal acoustic meatus of the temporal bone.

I Olfactory Nerve

transmits smell from the nasal mucosa to the brain and thus functions as a sensory or afferent nerve. It enters through the perforations in the crib form plate of the ethmoid bone to join the olfactory bulb in the brain