Nerves and the Nervous System
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Transcript of Nerves and the Nervous System
Nerves and the Nervous SystemOral Implications and Dental Considerations
Nerves and how they work
Overview of the different Nervous Systems
Cranial Nerves
Focus on Facial and Trigeminal Nerves
Nervous System Disorders
Clinical Considerations: Anesthesia
Case Study: Multiple Sclerosis
Nerves Neuron: A functional cell of the nervous system. The cell is composed of an axon,
cell body, and dendrite.
Nerve: A bundle of neurons.
Afferent Nerve: Sensory nerve that sends signals from the periphery of the
body to the CNS.
Efferent Nerve: Motor nerve that sends signals from the CNS to the periphery
of the body.
Ganglion (Ganglia): An accumulation of cell bodies outside the CNS.
Synapse: A junction between two neurons or between a neuron and an effector
organ.
Innervaition: A supply of nerves to a body part.
How Nerves Work1. There is an “equal” distribution of electrical charges and ions inside and
outside the neuron cell membrane. The outside of the cell is more positive (Na) and the inside cell is more negatively charged (K). The charge difference is called Resting potential. This balance of ions is maintained by Sodium-Potassium pumps.
2. An Action potential occurs when the cell membrane depolarizes allowing sodium ions to rush inside the cell. The action potential moves down the cell at an alarming rate. Sodium and potassium pumps work together to reestablish resting potential.
3. When a impulse reaches a synapse, the cell uses chemical agents called Neurotransmitters to relay the impulse to the next nerve or tissue.
Central Nervous System (CNS) Composed of brain and spinal cord.
Meninges: membrane that has three layers; Dura mater, arachnoid
mater. And pia mater.
Cerebrum – two cerebral hemispheres.
Cerebellum
Brainstem: Includes medulla, pons, midbrain.
Diencephalon: Thalamus and hypothalamus.
Surrounded and protected by bone.
Peripheral Nervous System (PNS)
Network of 43 pairs of
motor and sensory nerves
that connect the brain and
spinal cord to the rest of
their body
Control functions of
sensation, movement, and
motor coordination
Includes nerves such as the
femoral, radial, ulnar,
brachial plexus, and sciatic.
Autonomic Nervous System (ANS) Conveys sensory impulses from the blood vessels, the heart, and all of the
other organs in the chest, abdomen, and pelvis through nerves to other parts
of the brain
Impulses do not reach our consciousness, elicit mostly automatic or reflex
responses
Consists of sympathetic and parasympathetic divisions, either fight or flight
or rest and digest.
Overview of Cranial Nerves
12 pairs of nerves that go directly from the brain to specific areas of the head and neck
Some are involved in special senses
Some are involved in muscle movement and gland regulation
Nerves are named and numbered according to their location from the front of the brain to the back
Cranial Nerve I/Olfactory Nerve
Type of Nerve: Afferent – special sensory for smell.
Origin: Nerve enters the skull through the perforations in the cribriform plate of the ethmoid bone to join the olfactory bulb in the brain
Transmitting Foramen: Olfactory Foramina
Innervates: Transmits smell from the olfactory mucosa to the brain
Cranial Nerve II/Optic Nerve
Type of Nerve: Afferent – special
sense of vision
Origin: Nerve enters the skull
through the optic canal of the
sphenoid bone on its way to the
retina. Right and left optic nerves
join at the optic chiasma, many of
the fibers cross and continue into
the brain as the optic tracts.
Transmitting Foramen: Optic
Canal
Innervates: Transmits sight from
the retinal ganglionic layer to the
brain
Cranial Nerve III/Oculomotor Nerve
Type of Nerve: Efferent
Origin: Lateral wall of the cavernous sinus, carries preganglionic
parasympathetic fibers to the ciliary ganglion near the eyeball, and
postganglionic fibers to the small muscles inside the eyeball.
Transmitting Foramen: Superior Orbital Fissure
Innervates: Two components control muscles for precise eye movement
(Somatic Motor) and control pupillary light and accommodation reflexes
(Visceral Motor).
Cranial Nerve IV/Trochlear Nerve
Type of Nerve: Efferent
Origin: Runs in the wall of the cavernous sinus and goes to the orbit.
Transmitting Foramen: Superior Orbital Fissure
Innervates: The superior oblique muscle of the eye which is responsible
for eye movement, tracking, and fixation on an object
Cranial Nerve VI/Abducens Nerve
Type of Nerve: Efferent
Origin: Runs through the sinus, close to the internal carotid artery on its
way to the orbit
Transmitting Foramen: Superior Orbital Fissure
Innervates: The lateral rectus muscle which is also responsible for eye
movement, tracking, and fixation on an object
Cranial Nerve VIII / Vestibulocochlear Nerve
Type of nerve: Afferent Nerve – Sensory for hearing and balance.
Origin: The nerve attaches to the brain at the junction of the pons and
medulla oblongata, just lateral to the origin of the facial nerve.
Transmitting Foramen: Nerve enters cranial cavity through the internal
acoustic meatus of the temporal bone.
Innervates: Connects brain to inner ear.
Cranial Nerve IX / Glossopharyngeal Nerve Type of nerve: Efferent and afferent nerve
Origin: Arises from the anterior portion of the posterolateral sulcus of the
medulla oblongata.
Transmitting Foramen: Jugular foramen
• Innervates:
(Efferent) Innervates the pharyngeal muscle, the stylopharyngeus muscle, and the
preganglionic gland parasympathetic innervation for the parotid salivary gland.
(Afferent) Innervates the oropharynx and deals primarily with taste and general sensation
for base of the tongue and the gag reflex.
Additionally, the lesser petrosal nerve of IX, synapses with the otic ganglion.
Cranial Nerve X / Vagus Nerve Type of nerve: Afferent and Efferent nerve.
Origin: Arises from the lateral aspect of the medulla oblongata just below the ipsilateral glossopharyngeal nerve. It is the longest cranial nerve.
Transmitting Foramen: Jugular foramen.
Innervates:
(Afferent) Innervates parasympathetically to many organs in the thorax and abdomen such as the heart, thymus, and stomach. It also innervates the skin around the ear and taste sensation, and the epiglottis.
(Efferent) Innervates muscle of soft palate, pharynx, and larynx.
Cranial Nerve XI / Accessory Nerve Type of nerve: Efferent nerve.
Origin: Originates as two roots: one from the medulla oblongata adjacent
to the origin of the vagus nerve; the second from the cervical spinal cord.
Transmitting Foramen: Jugular foramen.
Innervates: Innervates the trapezius and sternocleidomastoideus muscles.
Additionally, it innervates muscles of the soft palate and pharynx.
Cranial Nerve XII / Hypoglossal Nerve Type of nerve: Efferent Nerve.
Origin: Arises as 10 to 15 rootlets from the anterolateral sulcus between
the olive and pyramid of the medulla oblongata.
Transmitting Foramen: The ipsilateral hypoglossal canal of the occipital
bone.
Innervates: Innervates muscles the intrinsic and extrinsic muscles of the
tongue.
Cranial Nerve VII/Facial Nerve
Type of Nerve: Afferent and Efferent components
Origin: The main trunk of the nerve emerges from the skull and gives off two
branches, the posterior auricular nerve and a branch to the posterior belly of the
digastric and stylohyoid muscles. It also sends off small efferent branches to
the stapedius muscle and two other branches to the ear. There are also a
multitude of smaller nerves that go off into the muscles of the face.
Transmitting Foramen: Mainly the Stylomastoid Foramen
Branches of the Facial Nerve:
Greater Petrosal Nerve
Chorda Tympani Nerve
Posterior Auricular, Stylohyoid, and Posterior Digastric Nerves
Temporal Branch
Zygomatic Branch
Mandibular Branch
Buccal Branch
Cervical Branch
Greater Petrosal Nerve
Type of Nerve: Afferent and Efferent
Origin: Branch off the facial nerve before it exits the skull, carries
preganglionic parasympathetic fibers
Innervates: Parasympathetic fibers go to the pterygopalatine ganglion and
then join with branches of the maxillary nerve which is carried to the
lacrimal gland, nasal cavity, and minor salivary glands of the hard and soft
palate. The afferent nerve fibers of the greater petrosal nerve go to the
palate for taste sensation.
Chorda Tympani Nerve
Type of Nerve: Afferent and Efferent
Origin: Branches off the facial nerve within the petrous portion of the
temporal bone and crosses the eardrum before exiting and traveling down
to the lingual nerve along the floor of the mouth
Transmitting Foramen: Petrotympanic Fissure (behind the TMJ)
Innervates: Parasympathetic efferent fibers innervate the submandibular
and sublingual salivary glands, afferent fibers are found in the body of the
tongue for taste sensation.
Posterior Auricular, Stylohyoid, and Posterior
Digastric Nerves Types of Nerves: All are Efferent nerves
Origins: Branches of the facial nerve after it exits the stylomastoid
foramen
Innervates: Posterior auricular nerve goes to the occipital belly of the
epicranial muscle. The stylohyoid innervates the stylohyoid muscle. The
posterior digastric nerve innervates the posterior belly of the digastric
muscle
Branches to the Muscles of Facial Expression
Types of Nerves: All five branches are efferent
Origins: These branches of the facial nerve originate in the parotid salivary
gland and then go to the muscles they supply
Innervates:
Temporal: Muscles anterior to the ear, frontal belly of epicranial muscle, superior
portion of orbicularis oculi, and corrugator supercili
Zygomatic: Inferior portion of orbicularis oculi and zygomatic minor and major muscles
Buccal: Muscles of upper lip and nose, buccinators, risorius, and orbicularis oris
Mandibular: Muscles of lower lip and mentalis muscle
Cervical: Runs inferior to the mandible to supply platysma
Cranial Nerve V / Trigeminal Nerve Type of nerve: Efferent and afferent nerve.
Afferent - The sensory component is thick.
Efferent - The motor component is thin.
Origin: Emerges from the inferolateral aspect of the pons. The trigeminal
nerve is the largest cranial nerve in diameter and is composed of a thin
efferent nerve and a thick afferent nerve. At the sight of the trigeminal
ganglion (located within the skull), the nerve divides into three anatomical
branches and exits through transmitting foramen.
Branches of the Trigeminal Nerve:
1. Ophthalmic Nerve (V1)
2. Maxillary Nerve (V2)
3. Mandibular Nerve (V3)
Ophthalmic Nerve (V1) Type of nerve: Afferent nerve. Is the smallest division.
Transmitting Foramen: Superior Orbital Fissure.
Innervates: Innervates the conjunctiva, cornea, eyeball, orbit, forehead, and ethmoidal and frontal sinsuses.
Three major nerves:
1. Frontal Nerve – Composed of supraorbital nerve and supratrochlear nerve. This nerve courses along the roof of the orbit.
2. Lacrimal Nerve – This nerve supplies the conjunctiva and the lacrimal gland. Additionally it also delivers the postganglionic parasympathetic nerve to the lacrimal gland.
3. Nasociliary Nerve – Composed of several nerves including the infratrochlear nerve, ciliary nerves, anterior ethmoidal nerve, external nasal nerve, and internal nasal nerves. These nerves innervates the skin of the eyelids, lacrimal sac, eyeball, and the nose.
Maxillary Nerve (V2) Type of nerve: Afferent Nerve.
Transmitting Foramen: Foramen rotundum of sphenoid bone.
Other nerve branches: within the pterygopalatine fossa the main maxillary trunk
diverges into many nerves, the largest being the infraorbital nerve. Other nerves include
the zygomatic, the anterior, middle, and posterior superior alveolar nerves, the greater
and lesser palatine nerves, and nasopalatine nerves. Additionally, within the
pterygopalatine fossa the pterygopalatine ganglion can be found. This ganglion caries
parasympathetic fibers from the facial nerve, and caries parasympathetic fibers to minor
salivary glands.
Innervates: Innervates the maxillae, overlying skin, maxillary sinuses, nasal cavity,
palate, and nasopharynx.
Maxillary Nerve (V2) Continued1. Zygomatic nerve – divides into the zygomaticofacial and zygomaticotemporal nerves. It
exits the pterygopalatine fossa through the inferior orbital fissure. These nerve innervate the
skin of the cheeks and the temporal regions.
2. Infraorbital Nerve – Branches into nerves that innervate the upper lip, medial part of the
cheek, lower eyelid, and side of the nose. Emerges from the Infraorbital foramen.
3. Anterior Superior Alveolar Nerve – Innervates maxillary central incisors, lateral incisors,
and canines, as well as the surrounding tissue.
4. Middle Superior Alveolar Nerve – Innervates maxillary premolar teeth and mesiobuccal
root of the maxillary first molar and their associated periodontium and buccal gingiva.
Maxillary Nerve (V2) Continued5. Posterior Superior Alveolar Nerve – Innervates most parts of maxillary teeth,
periodontium, buccal gingiva, and maxillary sinus.
6. Greater Palatine Nerve – Also known as the anterior palatine nerve, its located between
the mucoperiosteum and the bone of the posterior hard palate. Innervates the posterior hard
palate and posterior lingual gingiva.
7. Lesser Palatine Nerve – Also known as the posterior palatine nerve, it innervates the soft
palate and palatine tonsils.
8. Nasopalatine Nerve – Innervates the anterior hard palate, anterior lingual gingiva, and
nasal septum tissue.
Mandibular Nerve (V3) Type of nerve: Afferent and efferent nerve. This is the largest of the three
branches.
Transmitting Foramen: Foramen ovale of sphenoid bone.
Innervates:
(Efferent) innervates muscles of mastication.
Muscles of mastication include: Temporal, masseter, and lateral pterygoid muscles.
(Afferent) innervates skin, mucous membranes, gingiva, tongue, and periodontium.
Several nerve branches arise from the mandibular nerve (V3)
Mandibular Nerve (V3) Continued Meningeal branches – Afferent nerves for
parts of the dura mater.
Buccal nerve – Afferent nerve that
innervates the skin of the cheek, buccal
mucous membrane, and buccal gingiva near
mandibular posterior teeth.
Muscular branches – Efferent Nerves
Deep Temporal Nerves – two nerves
(anterior and posterior) .
Masseteric Nerve
Lateral Pterygoid Nerve
Medial Pterygoid Nerve – Efferent nerve
that innervates the medial pterygoid, tensor
tympani, and tensor veli palatini muscles.
Auriculotemporal Nerve – Afferent nerve
that innervates external ear and scalp. This
nerve also caries postganglionic
parasympathetic nerve fibers to the parotid
salivary gland.
Mandibular Nerve (V3) Continued Lingual Nerve – Afferent nerve that supplies general sensation for the body of the
tongue (anterior 2/3), floor of mouth, lingual gingiva, and mandibular teeth.
Inferior Alveolar Nerve – Afferent nerve that divides into the incisive and mental
nerves.
Mental Nerve – Afferent nerve that emerges from the mental foramen and supplies the
chin, lower lip, and labial mucosa.
Incisive Nerve – Afferent nerve which innervates mandibular premolars and anterior
teeth and periodontal tissue.
Mylohyoid Nerve – Efferent nerve that innervates the mylohyoid muscle and anterior
belly of the digastric muscle.
Disorders of the Nervous System
The nervous system can be damaged by
trauma, infection, genetic defects,
degeneration, tumors, autoimmune disease, and
blood flow disruption
Signs of a disorder can be loss of feeling,
tingling, persistent headaches, memory loss,
double vision, weakness, tremors, seizures,
lack of coordination, and change in mental
ability
Categories of Nervous System Disorders
Vascular Disorders: Stroke, transient ischemic attack (TIA), subarachnoid hemorrhage, subdural hemorrhage and hematoma, and extradural hemorrhage’
Infections: Meningitis, encephalitis, polio, and epidural abscess
Structural Disorders: Brain or spinal cord injury, Bell's palsy, cervical spondylosis, carpal tunnel syndrome, brain or spinal cord tumors, peripheral neuropathy, and Guillain-Barrésyndrome
Functional Disorders: Headache, epilepsy, dizziness, and neuralgia
Degeneration: Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis (ALS), Huntington's chorea, and Alzheimer's disease
Case Study: Oral Implications of MS
Multiple Sclerosis is an autoimmune disorder
that affects about 400,000 people in the U.S.
Affects Central Nervous System by damaging
myelin sheath around the nerves
Symptoms may include numbness, tingling,
weakness, fatigue, dizziness, blurring vision
Oral manifestations commonly include
paresthesia and facial palsy
Case Study: Oral Implications of MS
54 year old Caucasian male with MS since the age of 19
Healthy gingival tissues with slight xerostomia (due to medications), slight bleeding on probing
Severe attrition and some hyperkeratinization due to bruxism from muscle spasticity
Plaque score of 57% with most of it found interproximally
Very motivated and educated patient who just needed slight adjustments for better oral care
Showed how to angle brush 45 degrees and floss in a C shape for improved plaque removal
Every patient is an individual and needs an individual treatment plan, help those who have chronic illnesses improve their oral health
Review
Nerves control what we feel, how we feel it, and how we respond
to it.
The nervous system has different divisions and each are
interrelated and have coordinating functions
We have 12 pairs of cranial nerves that have special sensory,
motor, and regulatory functions
The facial and trigeminal nerves are absolutely essential to
understand as dental professionals
It is important to understand nervous system disorders and nerve
damage when dealing with people who have chronic illnesses or
conditions or when administering anesthesia.
ReferencesFacial Nerve Branches. (n.d.). Retrieved November 10, 2014, from
http://www.meddean.luc.edu/lumen/MedEd/grossanatomy/h_n/cn/cn1/cnb7.htm
Fatima, S. (n.d.). The Cranial Nerves. Retrieved November 10, 2014, from http://tsdocs.org/downloads/CranialNerves.pdf
Fehrenbach, M. J., Herring, S. W. (2012). Illustrated Anatomy of the Head and Neck (4th ed.). St. Louis, Missouri: Elsevier Saunders.
Hasudungan, A. (2013). Pharmacology – Local Anesthetic, Retrieved from http://www.youtube.com/watch?v=K_qjguv2Wtg
Hines, S., Lynch, P., Stewart, W., & Jaffe, C. (1998, March 22). Cranial Nerves - Contents. Retrieved November 10, 2014, from http://www.yale.edu/cnerves/contents.html
Homan, D. P., Shively, M. J. (2008). Fundamental Concepts of Human Anatomy. Eden Prairie, Minnesota: Bluedoor, LLC.
References
Overview of Nervous System Disorders. (n.d.). Retrieved November 10, 2014, from http://www.hopkinsmedicine.org/healthlibrary/conditions/nervous_system_disorders/overview_of_nervous_system_disorders_85,P00799/
Peripheral Nerve System. (n.d.). Retrieved November 10, 2014, from http://www.hopkinsmedicine.org/neurology_neurosurgery/centers_clinics/peripheral_nerve_surgery/conditions/peripheral_nerve_system.html
Reich, M., & Campbell, P. (2010, January 1). The Oral Implications of MS. Retrieved November 10, 2014, from http://www.dimensionsofdentalhygiene.com/ddhright.aspx?id=6992
Rubin, M. (2014, October 1). Overview of the Cranial Nerves. Retrieved November 10, 2014, from http://www.merckmanuals.com/home/brain_spinal_cord_ and_nerve_disorders/cranial_nerve_disorders/overview_of_the_cranial_nerves.html
Streeten, D. (n.d.). The Autonomic Nervous System. Retrieved November 10, 2014, from http://www.ndrf.org/ans.html