Nervous System: Central nervous system = Brain + spinal cord.
■ Peripheral nervous system = Somatic.
■ Autonomic system = Visceral.
■ Myenteric nervous system = GI, intrinsic.
Cerebral cortex’s Gray matter consist externally of = (6 layers)
Fucntions of Cerebral Cortex : Motor speech (Broca’s) area = (44, 45), Primary auditory cortex = (41, 42), Associative auditory cortex (Wernicke’s area) = (22) , Principal visual cortex = (17) , Principal sensory areas = (3, 1, 2) , Principal motor area = (4) , Premotor area = (6) (part of extrapyramidal circuit) , Frontal eye movement and pupillary change area = (8) .
Diencephalon contributes to = Rathke’s pouch (forming part of posterior pituitary).
Ventral posterior medial (VPM) Nuclei of Thalamus controls =Facial sensation including Pain.
All cranial nerves (except Cranial Nerve I and II) originate from the = brain stem.
All cranial nerve motor nuclei have unilateral corticonuclear connections except=
■ CN VII: Upper third
muscles of facial
expression have
bilateral innervation.
■ CN XII: Genioglossus
muscles have = bilateral
motor innervation.
All cranial nerve sensory nuclei have unilateral representation except = hearing.
Hearing is bilateral; Person cant go deaf in one ear from a stroke to the unilateral temporal area.
Taste Sensation : Taste to the anterior 2/3 of the tongue is CN VII via the = chorda tympani and the posterior 1/3 by = CN IX. CN X caries taste fibers from the = palate.
PARASYMPATHETIC GANGLIA:
1: Pterygopalatine Ganglion supplies = Lacrimal Glands and Glands in Palate & Nose
2: Otic Ganglion supplies = Parotid Gland
3: Submandibular Ganglion supplies = SubMandibular, Sublingual small Salivary Glands.
4: Ciliary Ganglion supplies = Ciliary Muscles, Spincter pupillae, Dilator, Pupillae and Tarsal muscles.
Trochlear nerve: The smallest cranial nerve and the only cranial nerve that exits from the = posterior surface of the brain stem.
Blurred vision = with a lesion to any of = CN III, IV, VI.
Ptosis (drooping eyelid) and dilated pupil with = CN III injury (levator
palpebrae superioris and sphincter pupillae muscle).
Lesion CN VI = eye persistently directed toward nose (because of lateral rectus).
Horner’s syndrome:
Lesion of oculosympathic pathway (sympathetics don’t come from CNs but run with them; come from superior cervical ganglion, ciliospinal center of Budge); miosis, ptosis, hemianhidrosis, apparent enophthalmos.
Argyll Robertson pupil:
Think prostitute’s pupil—accommodates but does not react; also associated with syphilis. No miosis (papillary constriction) with either direct or consensual light; does constrict with near stimulus (accommodation-convergence). Occurs in = syphilis and diabetes.
V1 and V2 of Trigeminal Nerve are purely = sensory and V3 Trigeminal Nerve is both = sensory and motor.
The buccal nerve of V3 provides sensation to = the cheek; whereas the buccal branch of CN VII is motor to the = buccinator muscle.
CN V—Trigeminal Nerve: Largest cranial nerve. No parasympathetic fibers are contained with the trigeminal nerve at its origin.
Lingual nerve: A) General sensation: Anterior 2/3rd of tongue, floor of mouth, and mandibular lingual gingival.
Carries (from chorda tympani [VII]): Taste sensation: Anterior 2/3rd tongue.
C)Preganglionic parasympathetics: To submandibular ganglion.
Auriculotemporal nerve: A)Sensory: Front of ear & TMJ.
B)Postganglionic parasympathetic: To parotid gland.
Inferior alveolar nerve: A) Gives off nerve to mylohyoid and inferior dental plexus; terminates
as mental nerve.
Motor to = mylohyoid.
C) Sensory to = teeth, skin of chin, lower lip.
Mental nerve: Termination of inferior alveolar nerve.
Sensory to = skin of chin, skin, and mucous membrane of lower lip.
Ophthalmic Nerve (V1) Sensory supply to = the Upper eyelid, cornea, conjunctiva, frontal sinus, upper nasal mucosa and forehead.
Maxillary Nrve (V2) Sensory supply to = Lower eyelid, upper cheek, lip, gums, palate, nose, tonsils, hard palate and upper teeth.
Mandibular Nerve (V3) sensory supply to = Tongue (general), temporoauricular skin, lower face, lower teeth.
Motor Supply to = Muscles of mastication, tensor tympani, mylohyoid, anterior belly of digastric, tensor veli palatini
IMPORTANT BRANCHES OF TRIGEMINAL NERVE V3:
A) Lingual nerve:
General sensation: Anterior 2/3rd of tongue, floor of mouth, and mandibular lingual gingival. Carries (from chorda tympani [VII]):
Taste sensation: Anterior 2/3rd tongue.
Preganglionic parasympathetics: To submandibular ganglion.
Auriculotemporal nerve:
Sensory: Front of ear, TMJ.
Postganglionic parasympathetic: To parotid gland.
C) Inferior alveolar nerve:
Gives off nerve to mylohyoid and inferior dental plexus; terminates
as mental nerve.
Motor to: mylohyoid.
Sensory to : teeth, skin of chin, lower lip.
D) Mental nerve:
Termination of = inferior alveolar nerve.
Sensory to : skin of chin, skin, and mucous membrane of lower lip.
E) Motor branches: Motor to muscles of = mastication, anterior digastric, and so on.
INFERIOR ALVEOLAR NERVE BLOCK:
Anesthetize the mandibular teeth.
Block this branch of V3 as it enters the mandibular foramen.
Needle Course:
Pierces:
■ Buccinator (between palatoglossal and palatopharyngeal folds).
■ Lies lateral to = medial pterygoid at the mandibular foramen.
■ If the needle penetrates too far posteriorly can hit parotid gland and CN VII, it will lead to = Ipsilateral facial paralysis.
Lingual Nerve:
The lingual nerve is found in the = pterygomandibular space with the inferior alveolar nerve, artery, and vein.
The lingual artery does not run with = the lingual nerve. The lingual artery is = medial to the hyoglossus muscle, whereas the lingual vein and nerve are lateral to = the hyoglossus (as is the submandibular duct and hypoglossal nerve [XII]).
The submandibular duct is crossed twice by the = lingual nerve.
If the lingual nerve is cut after the chorda tympani joins, you lose both = taste and tactile sensation.
The lingual nerve: can be damaged with third molar extraction because it lies close to the mandibular ramus in the vicinity of the third molar.
TRIGEMINAL NUCLEI:
■ There are four paired nuclei (both motor and sensory).
Trigeminal Nerve:
All sensory information from the face is relayed through = VPM nucleus of
thalamus; sensory information from the rest of the body is through the = VPL.
From the thalamic nuclei (VPM or VPL), information relays to the = somatosensory
cortex (areas 3, 1, 2); the facial segment of the sensory homunculus
comprises a large area of the = lateral parietal lobe.
Parts of CNs VII and IX travel with = trigeminospinal tract.
All CN V afferent cell bodies are located within = trigeminal ganglion except
proprioceptive inputs.
Mesencephalic nucleus of CN V is the only case where primary sensory cell bodies are located within the = CNS, rather than in ganglia.
Touch & Pressure is carried by = A-beta fibers.
Pain & Temperature is carried by = A-delta and C-Fibers.
Proprioception is carried by = A-alpha Fibers.
Sensation in teeth can be misinterpreted in = ear (because of the cross innervation).
Herpes zoster often affects = V1 division.
Trigeminal neuralgia (tic douloureux) : can affect V2 and V3.
SENSATION OF EXTERNAL EAR:
A) Auriculotemporal nerve (V3) supplies = Anterior half of external ear canal and facial surface of upper part of auricle.
Auricular branch of vagus (CN X) supplies = Posterior half of external ear canal (so stimulation can cause reflex symptoms: eg, fainting, coughing, gagging).
C) Greater auricular nerve (C2, C3) supplies = Inferior auricle (anterior and posterior)
D) Lesser occipital nerve (C2, C3) supplies = Cranial surface of upper auricle.
Corneal reflex: If stimulating right eye:
■ Lesion R V1 = neither
eye blinks.
■ Lesion L V1 = bilateral
blink.
■ Lesion R VII = only left
eye blinks (indirect).
■ Lesion L VII = only right
eye blinks (direct).
Levator palpebrae superioris (CN III) keeps the eyelid open; lesion results in = ptosis.
Orbicularis oculi (CN VII) closes eyelid; lesion results in inability to close, no corneal reflex.
TRIGEMINAL LESIONS:
Sensory: Division V1, 2, 3 = Deficits along distribution (pain, temperature, touch, pressure, proprioception)
Motor: Division V3 only =
Temporalis and masseter muscles
■ Ipsilateral weakness of jaw closure
■ Ipsilateral open bite
Pterygoid muscle
■ Weakness of jaw opening
■ Deviation to ipsilateral side on opening
Diminished/loss of reflexes.
Facial Nerve passes through = Facial Canal.
CN VII NUCLEI:
A) Main motor nucleus
Superior salivatory Nucleus
C) Nucleus of the solitary tract (gustatory nucleus)
IMPORTANT MUSCLES OF FACIAL EXPRESSION (ALL CONTROLLED BY CN VII):
A) Orbicularis Oris : Whistle, Pulls lips against teeth, protrudes lips.
Depressor anguli Oris: Frown, Pulls down angle of mouth.
C) Zygomaticus Major: Smile, Pulls angle of mouth up and back.
D) Risorius: Smile, Pulls angle of mouth laterally.
E) Orbicularis oculi: Closes eye.
OTHER MUSCLES CONTROLLED BY CN VII:
A) Buccinator: Holds food on occlusal table (accessory muscle of mastication); tenses cheek (blowing, whistling)
Stapedius: Decreases vibration of the stapes (decreases perception of sound)
CN VII LESIONS:
A) Lower motor neuron lesion: Ipsilateral paralysis/weakness of upper and lower face; loss of corneal reflex (efferent limb).
Upper motor neuron lesion: Contralateral lower face weakness only.
Bell’s palsy: Acute 7th nerve palsy.
Stroke: is an example of = an upper motor neuron lesion.
Bell’s palsy: is an example of a = lower motor neuron lesion.
Facial and maxillary arteries supply blood to the = buccinator.
GREATER PETROSAL NERVE
A) carries Taste from = palate via palatine nerves.
Greater petrosal nerve is the parasympathetic root of the = pterygopalatine ganglion.
Central hearing connections are bilateral, so a central lesion will not cause deafness in = either ear.
Caloric test is testing the vestibuloocular reflex. COWS Cold Opposite Warm Same.
The gag reflex: is mediated by CN IX (afferent-unilateral) and CN X (efferent-bilateral).
CN IX—Glossopharyngeal:
A) Carries taste from = posterior third of the tongue.
Parasympathetic/secretomotor: Parotid via = otic ganglion.
C) Gag reflex (afferent limb) (fauces).
D) Chemo-, baroreception (afferent limb)—carotid body, carotid sinus.
Chemoreception: Carotid body; oxygen tension measurement.
Baroreception: Carotid sinus; blood pressure changes. Mediated CN IX (afferent) and CN X (efferent).
Vagus nerves: lose their identity in the esophageal plexus. The anterior gastric nerve can be cut (vagotomy) to reduce gastric secretion.
The cardiac branches of the vagus: (form the cardiac plexus) are preganglionic parasympathetic nerves that synapse with postganglionic parasympathetic nerves in the = heart.
The abdominal viscera below the left colic flexure (and genitalia and pelvic viscera) are supplied by = pelvic
splanchnic nerves (parasympathetic preganglionics).
With CN XII paralysis, the tongue tends to fall back and obstruct the airway (genioglossus).
CN XI LESIONS:
A) Paralysis of SCM: difficulty turning head to = contralateral side.
Paralysis of trapezius: Shoulder droop.
In addition to deviation to the affected side (with damage to CN XII/hypoglossal Nerve and resultant denervation atrophy), dysarthria (inability to articulate) can be experienced by the patient.
Hypoglossal Nerve: Passes between External Carotid Artery and Internal Jugular Vein.
CN XII LESIONS:
A) Lower motor neuron: Tongue deviates toward side of =lesion.
Upper motor neuron: Tongue deviates away from side of = lesion.
Spinal Cord:
A) 40–45 cm long.
Extends to L1–L2 (L3 in a child).
CSF: is located in the = subarachnoid space. This space is entered during a = lumbar “tap” or puncture.
In the spinal cord, white matter is peripheral and gray matter is central, the reverse of the = cerebral cortex.
The spinal cord is protected by the = bony and ligamentous walls of the = vertebral canal and CSF.
The cell bodies for afferent/sensory nerves are located in the = dorsal root ganglion.
Tracts:
A) Ascending/sensory:
a) Anterior spinothalamic = Touch, pressure.
b) Lateral spinothalamic = Pain, temperature
c) Posterior columns (gracilis and cuneatus) = Proprioception, position sense.
d) Spinocerebellar = Motor coordination, proprioception.
Descending/motor:
a) Corticospinal = Motor
b) Tectospinal = Movement of head
c) Rubrospinal = Muscle tone, posture, head, neck, upper extremities
d) Vestibulospinal = Equilibrium (interface with CN VIII)
e) Reticulospinal = Muscle tone, sweat gland function
NERVE FIBER TYPES:
A) A Fiber:
a) A-α: Proprioception & Motor
b) A-β: Sensory, Touch and Pressure
c) A-γ: Muscle spindle
d) A-δ: Sharp pain, Temperature and Touch
B Fiber: Preganglionic autonomic.
C) C Fiber: Dull pain, Temperature, Postganglionic and autonomic.
Splanchnic nerves: are sympathetic nerves to the = viscera. They pass through the sympathetic chain ganglia without synapse (exceptions to short preganglionic and long postganglionic) and synapse in the effector.
Sympathetic Nervous System :
■ Thoracolumbar
■ “Fight or flight”
Parasympathetic Nervous System :
■ Craniosacral.
■ “Rest and digest.”
Postganglionic autonomic fibers: are unmyelinated = C-fibers.
Gray rami: connect sympathetic trunk to every = spinal nerve.
White rami: are limited to = spinal cord segments between T1 and L2.
Cell bodies of the visceral efferent preganglionic fibers (visceral branches of sympathetic trunk) are located in the = interomediolateral horn of the spinal cord.
Cell bodies of visceral afferent fibers are located in the = dorsal root ganglia