Nerves Flashcards
nervous system
Nervous system is an extensive, intricate network of neural structures that activates, coordinates, and controls all functions of the body.
function of nervous system
carry messages or impulses based on electrical action potentials
nerve
a bundle of neural processes outside the central nervous system and in the peripheral nervous system.
synapse
the junction between two neurons or between a neuron and an effector organ, where neural impulses are transmitted.
innervation
A supply of nerves to a specific body part that allows for information to be carried back & forth from body part to brain.
ganglion
An accumulation of neuron cell bodies outside the central nervous system
nodes of ranvier
Gap in the myelin sheath, allowing for faster conduction of impulses
how do impulses travel
Impulse travels along myelinated axons via saltatory conduction
how much of a nerve has to be covered with local anesthetic
8-10mm
central nervous system
Consists of brain & spinal cord
Surrounded by bone
peripheral nervous system
Consists of all the nervous tissue outside of these organs
Somatic – operates with conscious control
Autonomic – operates without conscious control
Sympathetic – “fight or flight”
Parasymphetic – “rest or digest”
afferent
sensory
Carries information from the periphery of body TO the brain
Taste, pain, proprioceptionProprioception: info about movement, equilibrium & positioning of the body
efferent
motor
Carries information AWAY (exiting) the brain to periphery of body
Gives orders to muscles to activate them
2 Divisions:
Somatic & Autonomic
somatic nervous system
Includes all nerves controlling the muscular system & external sensory receptors
Operates with conscious control
Autonomic Nervous System
“Caretaker of the body”
Operates without conscious control (it just does it)
Has 2 divisions:
Sympathetic
Parasympathetic
Sympathetic
Fight or flight
Response leads to hyposalivation = dry mouth
Parasympathetic
Rest or Digest
Response leads to stimulation of salivary glands
Saliva flow aids in digestion
Peripheral nervous system two types of nerves
sensory, efferent
afferent
Carries information from the periphery of body TO the brain
Taste, pain, proprioceptionProprioception: info about movement, equilibrium & positioning of the body
efferent
Carries information AWAY (exiting) the brain to periphery of body
Gives orders to muscles to activate them
2 Divisions:
Somatic & Autonomic
Somatic nervous system
Includes all nerves controlling the muscular system & external sensory receptors
Operates with conscious control
Autonomic Nervous System
“Caretaker of the body”
Operates without conscious control (it just does it)
Has 2 divisions:
Sympathetic
Parasympathetic
cranial nerves
Emerge from the inferior surface of the brain
All pass through the foramina of the skull & innervate structures in the head, neck, & facial region
Cranial Nerve I – Olfactory
Afferent (sensory)
Transmits smells from the nasal mucosa to the brain
Enters skull through cribriform plate in the ethmoid bone
Cranial Nerve II – Optic
Afferent (sensory)
Transmits sight from the retina to the brain
Enters skull through the optic canal of the sphenoid bone
Cranial Nerve III – Oculomotor
Efferent (motor)
Moves the eyeball & constricts pupil
Runs in the lateral wall of cavernous sinus
Exits skull through the superior orbital fissure of sphenoid bone
Cranial Nerve IV – Trochlear
Efferent for one eye muscle, proprioception
Runs in the lateral wall of cavernous sinus
Exits skull through the superior orbital fissure of sphenoid bone
Cranial Nerve V – Trigeminal
Sensory & Motor
Efferent to muscles of mastication & some cranial muscles
Afferent to teeth, tongue, oral cavity, skin of face & head
Three branches
Cranial Nerve V – Trigeminal origin and branches
Within the skull (temporal bone) this nerve has a bulge called the Trigeminal Ganglion
Anterior to the ganglion, the nerve divides into 3 branches
V1 Ophthalmic Sensory
V2 Maxillary Sensory
V3 Mandibular Sensory & Motor
Cranial Nerve VI – Abducens
Efferent for one eye muscle
Runs near the internal carotid artery, often affected by infections of the sinus
Exits skull through the superior orbital fissure of sphenoid bone
Cranial Nerve VII – Facial
Afferent (Sensory) & Efferent (Motor)
Afferent (sensory) to skin behind ear, taste sensation & body of tongue
Efferent to muscles of facial expression, lacrimal gland, submandibular & sublingual salivary glands
Cranial Nerve VII – Facial branches
greater petrosal
chorda tympani
Postauricular
Stylohyoid
posterior digastric
In the parotid, it divides into branches to supply the muscles of facial expression
Cranial Nerve VIII – Vestibulocochlear (Auditory)
Afferent
Hearing & balance
Enters cranium through internal acoustic meatus
Cranial Nerve IX – Glossopharyngeal
Afferent for the pharynx for taste & general sensation from the base of the tongue
Efferent for the stylopharyngeus muscles & parotid salivary gland
Passes through jugular foramen
Cranial NerveX – Vagus
Afferent for skin around ear & taste, sensation of epiglottis
Efferent to muscles of soft palate, pharynx, & larynx
Passes through jugular foramen
Cranial Nerve XI – Accessory (Spinal)
Efferent to trapezius, SCM, muscles of soft palate & pharynx
2 roots: brain & spinal cord
Exits through jugular foramen
Cranial Nerve XII – Hypoglossal
Efferent for intrinsic & extrinsic muscles of the tongue
Exits through hypoglossal canal
What runs through the optic canal
optic nerve
what runs through superior orbital fissure
III Oculomotor
IV Trochlear
V-1 Ophthalmic branch of Trigeminal nerve
VI Abducens
Nerves to the Oral Cavity
V Trigeminal
V2- Maxillary
V3- Mandibular
VII Facial
IX Glossopharyngeal
XII Hypoglossal
Cranial Nerve V – Trigeminal
Sensory & Motor
Efferent to muscles of mastication & some cranial muscles
Afferent to teeth, tongue, oral cavity, skin of face & head
Three branches
Cranial Nerve V – Trigeminal
Within the skull (temporal bone) this nerve has a bulge called the Trigeminal Ganglion
Cranial Nerve V – Trigeminal (anterior ganglion)
Anterior to the ganglion, the nerve divides into 3 branches
V1 Ophthalmic Sensory
V2 Maxillary Sensory
V3 Mandibular Sensory & Motor
Cranial Nerve V – Trigeminal V1 - Ophthalmic
1st & smallest division of sensory root
Afferent (sensory) for conjunctiva, cornea, eyeball, orbit, forehead & ethmoid, frontal sinuses
Carries sensory information to brain through superior orbital fissure
Branches that join to form V1:
Frontal, lacrimal & nasociliary
3 Branches that form V1
Frontal – forehead, scalp, bridge of nose
Lacrimal – upper eyelid, lacrimal gland
Nasociliary – nasal cavity & paranasal sinuses
Cranial Nerve V – Trigeminal V2 - Maxillary
2nd division of sensory root
Afferent (sensory) for maxilla & overlying skin, maxillary sinuses, nasal cavity, palate, nasopharynx
Trunk formed in pterygopalatine fossa by convergence of many nerves: Infraorbital (largest contributor), zygomatic, ASA, MSA, PSA, greater & lesser palatine, nasopalatine
Enters skull through foramen rotundum
Cranial Nerve V – Trigeminal V2 – Maxillary Zygomatic Nerve
Afferent (sensory)
Merger of zygomaticofacial & zygomaticotemporal nerves in orbit
Enters through inferior orbital fissure to join maxillary nerve in pterygopalatine fossa
Cranial Nerve V – Trigeminal V2 – Maxillary Infraorbital Nerve
Afferent (sensory)
Merger of cutaneous branches from upper lip, medial cheek, lower eyelid, side of nose
Enters through infraorbital foramen (with infraorbital blood vessels) and is joined by ASA, MSA, &PSA
Cranial Nerve V – Trigeminal V2 – Maxillary Anterior Superior Alveolar (ASA) Nerve
Afferent (sensory)
Sensation for maxillary anterior teeth, pulp, periodontium & overlying facial gingiva
Joins the infraorbital nerve in infraorbital canal
Cranial Nerve V – Trigeminal V2 – MaxillaryMiddle Superior Alveolar (MSA) Nerve
Afferent (sensory)
Sensation for maxillary premolars & mesiobuccal root of 1st maxillary molars. Surrounding gingiva & periodontium
Not everyone has an MSA! Only 28% of population
Joins the infraorbital nerve in infraorbital canal
Cranial Nerve V – Trigeminal V2 – Maxillary Posterior Superior Alveolar (PSA) Nerve
Afferent (sensory)
Sensation for maxillary molars, periodontium, buccal gingiva, & maxillary sinuses
Exits from posterior superior alveolar foramen on maxillary tuberosity
Can join the infraorbital nerve in infraorbital canal (if MSA is present) but most times it joins the maxillary nerve directly
Cranial Nerve V – Trigeminal V2 – Maxillary Greater Palatine (GP) Nerve
Afferent (sensory)
Sensation for posterior hard palate & lingual gingiva
Exits from greater palatine foramen
Ascend in pterygopalatine canal towards maxillary nerve
Cranial Nerve V – Trigeminal V2 – Maxillary Lesser Palatine (LP) Nerve
Afferent (sensory)
Sensation for soft palate & tonsillar tissues
Exits from lesser palatine foramen
Ascend in pterygopalatine canal towards maxillary nerve
Cranial Nerve V – Trigeminal V2 – Maxillary Nasopalatine Palatine (NP) Nerve
Afferent (sensory)
Sensation for anterior hard palate & lingual gingiva of anterior teeth
Originates in mucosa of anterior hard palate lingual of maxillary anterior teeth
Enters incisive foramen
Anastomoses with greater palantine nerve
Cranial Nerve V – Trigeminal V3 - Mandibular
Main trunk formed in infratemporal fossa, then passes through foramen ovale
Gives off meningeal & muscular branches before dividing into Anterior & Posterior trunks
Cranial Nerve V – Trigeminal V3 - Mandibular
Gives off meningeal & muscular branches before dividing into Anterior & Posterior trunks
Meningeal Branches
-Afferent (sensory) to dura matter
Muscular Branches
-Efferent (motor) to these muscles:
-lateral ptyergoid
-tensor tympani
-tensor veli palantini
Cranial Nerve V – Trigeminal V3 - Mandibular anterior trunk divisions
Buccal nerve
Deep temporal nerve
Masseteric nerve
Lateral Pterygoid nerve
Cranial Nerve V – Trigeminal V3 - Mandibular anterior trunk- Buccal nerve afferent
Afferent (sensory) for skin of cheek, buccal mucosa, buccal gingiva of mandibular teeth, cheek
Anesthetized with Buccal Nerve Block (BNB) to anesthetize the buccal gingiva of mandibular posterior teeth
Cranial Nerve V – Trigeminal V3 - Mandibular anterior trunk- Buccal nerve efferent
Deep Temporal (anterior/posterior)
Masseteric
Lateral Pterygoid
Cranial Nerve V – Trigeminal V3 - Mandibular posterior trunk branches
Auriculotemporal nerve
Lingual nerve
Inferior Alveolar nerve
Cranial Nerve V – Trigeminal V3 - Mandibular posterior trunk- AURICULOTEMPORAL nerve
Afferent (sensory) to external scalp, ear, & TMJ
Carries postganglionic parasympathetic nerve fibers to parotid salivary gland (from cranial nerve IX –glossopharyngeal)
Cranial Nerve V – Trigeminal V3 - Mandibular posterior trunk- lingual nerve
Afferent (sensory) to body of tongue, floor of mouth, lingual gingiva of mandibular teeth
Communicates with submandibular ganglion & chorda tympani
Anesthesized during the Inferior Alveolar (IA) nerve block injection
Cranial Nerve V – Trigeminal V3 - Mandibular posterior trunk- Inferior alveolar nerve
Afferent (sensory) to mandibular teeth
Travels within mandibular canal
Formed by merger of incisive & mental nerves
Joined by mylohyoid nerve as it exits from mandibular canal
Cranial Nerve V – Trigeminal V3 - Mandibular posterior trunk- Inferior alveolar nerve- THREE BRANCHES
-mylohyoid
-mental
-incisive
Mylohyoid
Efferent (motor) for mylohyoid muscle& anterior belly of digastric muscle
mental
Afferent (sensory) for chin, lower lip, labial mucosa, of mandibular anterior teeth
Exits mental foramen
incisive
Afferent (sensory) for anterior mandibular teeth
Joins with mental nerve to form Inferior Alveolar
Cranial Nerve VII – Facial
Afferent (Sensory) & Efferent (Motor)
Afferent (sensory) to skin behind ear, taste sensation & body of tongue
Efferent to muscles of facial expression, lacrimal gland, submandibular & sublingual salivary glands
Cranial Nerve VII – Facial branches
greater petrosal
chorda tympani
Postauricular
Stylohyoid
posterior digastric
In the parotid, it divides into branches to supply the muscles of facial expression
Cranial Nerve VII – Facial-Greater Petrosal (emergence and insertion)
Facial nerve emerges from brain & enters internal acoustic meatus in petrous part of temporal bone, where it gives off a small efferent branches to middle ear and two larger branches: the chorda tympani & the greater petrosal nerve
Cranial Nerve VII – Facial-Greater Petrosal
carries parasympathetic fibers
Efferent (motor) – fibers to pterygopalatine ganglion
Post-ganglionic fibers join with maxillary nerve to lacrimal gland, nasal cavity, & minor salivary glands of hard & soft palate
Afferent (sensory) – taste in palate
Cranial Nerve VII – Facial-Chorda Tympani (insertion and emergence)
Facial nerve emerges from brain & enters internal acoustic meatus in petrous part of temporal bone, where it gives off a small efferent branches to middle ear and two larger branches: the greater petrosal nerve & the chorda tympani
Cranial Nerve VII – Facial-Chorda Tympani
carries parasympathetic fibers
Efferent (motor) – submandibular & sublingual salivary glands
Afferent (sensory) – taste in the body of the tongue
Exits the petrotympanic fissure
Runs with lingual nerve (V3)
Communicates with submandibular ganglion
Cranial Nerve VII – Facial-Facial Branches (emergences and insertions)
Main trunk emerges from skull through stylomastoid foramen of temporal bone
Then passes through parotid & divides into superficial & deep lobes
Divides into numerous terminal branches to supply the muscles of facial expression
-posterior auricular
-stylohyoid
-posterior digastric
-temporal
-zygomatic
-buccal
-mandibular
-cervical
Cranial Nerve VII – Facial-Facial Branches
Main trunk emerges from skull through stylomastoid foramen of temporal bone
Then passes through parotid & divides into superficial & deep lobes
Divides into numerous terminal branches to supply the muscles of facial expression
-posterior auricular
-stylohyoid
-posterior digastric
-temporal
-zygomatic
-buccal
-mandibular
-cervical
facial paralysis
Loss of muscular action of the muscles of facial expression
Clinical Signs & Symptoms : drooping eyebrow, eyelid, and labial commissure, with a dribbling of saliva; lack of normal expression, close the eye or whistle, speech & eating difficulty
Can be bilateral or unilateral
Can be transient or permanent
Bell’s Palsy
Unilateral facial paralysis
No known cause
Loss of excitability to facial nerve
No treatment – but physical therapy & anti-inflammatory medications may help
Abrupt onset that spontaneously resolves within 6 months, may return later
Trigeminal Neuralgia
No known etiology
Afferent nerves of Trigeminal Nerve = Cranial Nerve 5
Signs & Symptoms: excruciating short-term pain (shock like or stabbing pain) when facial trigger zones are touched (often on one side). Between attacks there can be burning, throbbing, numbness, tingling, or dull aching.
Treatment: Peripheral neurectomy, anticonvulsant drugs, botox injections, muscle relaxants
AKA “tic douloureux”
