Ariculatory V - CN X and CN VII

what are the two CN pathways?

motor and sensory

what is the CN motor pathway?

brainstem nucleus → through skull opening → to muscles or glands

what is the CN sensory pathway?

receptors → through skull opening ←> ganglion → brainstem nucleus

what are the 4 fibre types of the vagus?

• branchial motor

• visceral motor

• visceral sensory

• general sensory

what does the brachial motor fibres of CN X innervate?

muscles of palate, pharynx, and larynx

what does the visceral motor fibres of CN X innervate?

smooth muscle & glands of pharynx, larynx, and thoracic and abdominal viscera

where do the visceral sensory fibres of CN X get sensation from?

from pharynx, larynx, trachea (caudal), esophagus, and thoracic & abdominal viscera (e.g., reflexes)

where do the general sensory fibres if CN X get sensation from?

from external ear & tympanic membrane, behind ear (e.g., pain), pharynx, larynx (above the vocal folds)

what are major functions of CN X branchial motor?

• velopharyngeal port and palatolingual contact

• cross-sectional volume in pharynx

• positioning and tension of VFs

what is the brainstem nucleus of CN X branchial motor?

nucleus ambiguus in medulla

what is meant by bilateral?

L feeds L and R brainstem, R feeds R and L brainstem, carries info fromboth sides of brain but only goes to designated side organs

how does CN X branchial motor leave the skull?

axons leave the R and L sides of the medulla, and exit the skull through the jugular foramen

what happens to CN X branchial motor outside the skull?

once leaving, it branches off to Xph, SLN, or RLN

what happens to CN X BM in the pharyngeal nerve (Xph) branch?

divides into pharyngeal plexus to supply muscles of soft palate and pharynx

what happens to CN X in the superior laryngeal nerve (SLN) branch?

descends adjacent to pharynx; divides into internal (afferent) and external (efferent) SLNs; eSLN supplies cricothyroid muscle

what happens to CN X BM in the recurrent laryngeal nerve branch?

takes different path on right and left sides of body

what happens with RLN on the right?

– RLN branches from Vagus anterior to subclavian artery

– hooks under the subclavian artery & ascends posterior to it, in a groove between trachea and esophagus

what happens with RLN on the left?

– RLN branches from Vagus anterior to the aortic arch

– hooks under aortic arch, ascends through superior mediastinum to reach groove between trachea and esophagus

what is meant by ‘recurrent’?

went down and came back up, sides differ in where they reoccur

which muscle of the pharynx does CN X BM not innervate?

stylopharyngeus

which muscle of the soft palate does CN X BM not innervate?

tensor veli palatini

which intrinsic laryngeal musle isn’t innervated by the RLN branch of CN X BM?

cricothyroid (SLN)

What is visceral motor?

parasympathetic (not voluntary) motor

what are some examples of the the major function of CN X VM?

– stimulates digestive secretions

– dilates blood vessels

– slows heart rate

what is the brainstem nucleus of CN X VM?

cells bodies in dorsal motor nucleus (DMNX; gut, lungs, liver, pancreas) and nucleus ambiguus (cardiac plexus) in medulla

what does CN X VM recieve input from?

receives input from hypothalamus, olfactory system, reticular formation, nucleus tractus solitarius (NTS)

how does CN X exit the skull?

fibres exit skull via jugular foramen

how do CN X VM get to the pharynx and larynx?

axons travel with the pharyngeal branch (Xph) and SLN, secretomotor activation of glands in pharyngeal and laryngeal mucosa

how do CN X VM get to the thorax and abdomen?

secretomotor activation of glands and smooth muscle (esophagus, lungs, heart, stomach, liver, etc)

what is viceral sensory?

sensation driving reflexes and homeostasis (life sustaining central pattern generators)

what are the reflexes driven by CN X VS

gag reflex, laryngeal adductor reflex, and cough reflex

what central pattern generators are altered by CN X VS?

respiratory rhythm, cardiac rhythm

where are the receptors for the true vocal folds and lower larynx?

dendrites join the RLN

which reflex does the RLN drive?

cough reflex

where are the receptors for the pharynx and upper larynx?

dendrites create the internal branch of the Superior Laryngeal Nerve (iSLN)

what reflex/receptors are driven by iSLN?

swallow

where do iSLN exit the laryngeal cavity?

exit the laryngeal cavity through opening in the thyrohyoid membrane & join the eSLN

where are the receptors for the soft palate and pharynx?

pharyngeal branch of the vagus

which reflex is driven by the pharyngeal branch of the vagus?

gag reflex

where are CN X VS strecth receptors?

in walls of aortic arch

where are CN X VS chemnoreceptors?

in aortic bodies adjacent to aorta

where are CN X VS taste receptors?

from pharynx, epiglottis, and laryngeal aditus

what is the inferior vagal ganglion?

where cell bodies of the visceral sensory fibres of the vagus are contained

how does CN X VS pass through the skull?

via the jugular foramen

where do CN X VS primary neurons synapse in the brainstem?

axons synapse (with secondary neurons) in the nucleus tractus solitarius in the medulla

what is the nucleus tractus solitarius?

where CN X VS synapse in brainstem

where do secondary CN X VS neurons synapse in brainstem?

axons synapse in hypothalamus, reticular formation and DMNX for parasympathetic reflexes (with visceral motor pathway), and with nucleus ambiguus for reflexes

what is meant by general sensory?

concious appreciation of feeling something there

what is CN X GS?

concious sensations from skin at back of the ear and in the external auditory meatus, external surface of tympanic membrane, pharynx, larynx

what are the major functions of CN X GS?

• conscious perception of touch

• may be important in voluntary control of VFs during vocalization (fine movements and control of tension)

where are the ear receptors forCN X GS?

dendrites join the RLN, SLN and Xph from the pharynx, larynx

what is the superior vagal ganglion?

where cell bodies of the general sensory fibres are contained

where do the CN X GS fibres leave through the skull?

via the jugular foramen

where do the CN X GS primary neurons synapse in the brainstem?

axons synapse in the nucleus of the spinal tract (CN V sensory system)

what is the nucleus of the spinal tract?

CN V sensory system, but also where CN X primary neurons synapse

where do the CN X GS secondary neurons ascend to in the brainstem?

the contralateral thalamus

where are the cell bodies of CN X GS tertiary neurons?

in thalamus, axons travel through internal capsule to primary somatosensory cortex

where are all the CN X fibres in the brain?

the medulla

how do all the CN X fibres get through the skull?

via the jugular foramen

how can we test for CN X function?

• soft palate tests

• laryngeal test

how do we test for voluntary soft palate control?

see how soft palate moves on ‘ah’

what do we look for in the ‘ah’ test?

symmetry and range of movement

what does asymmetry on ‘ah’ test tell us?

something happened to vagus after leaving skull, because it should be bilateral

how do we test autonomic function of soft palate?

gag reflex test

how do we test for laryngeal function?

test volitional control with ‘ah’ test, test cough

how is ‘ah’ evaluated for laryngeal function?

• maximum phonation time

• perceptual judgement of hoarseness, breathiness, pitch breaks

how do we test a cough for laryngeal function?

check for voluntary cough vs reflexive

which branch of the vagus is being tested when we test for laryngeal function?

RLN

what are the four CN VII fibre types?

• branchial motor

• visceral motor

• special sensory

• general sensory

what does CN VII BM innervate?

Innervates muscles of facial expression (& auricular muscles), plus the stapedius, stylohyoid, and the posterior belly of digastric

where are all muscles innervated by CN VII derived from?

second branchial arch

what does CN VII VM innervate?

innervates the lacrimal (tear) gland, submandibular and sublingual salivary glands, mucous membranes of nose and hard and soft palate

where does CN VII SS gain sensation from?

taste sensation (gustation) from the anterior 2/3 of tongue (palatopharyngeal tongue)

where does CN VII GS gain sensation from?

sensations from skin of concha of the external ear, skin behind ear, external auditory meatus, external tympanic membrane

what is an example of VN VII GS fibres at work?

sensations from around the ear so we can feel it before it goes in the ear and causes an issue

which fibres are separate from rest of CN VII nerve?

branchial motor fibres

what is the nervus intermedius?

fascial sheath where remaining CN VII fibres are bound after branchial motor is separated

where are CN VII BM in the brainstem?

cell bodies of the LMNs are in the facial motor nucleus in the pons

what is the lateralization of facial muscles above the eye?

bilateral

what is the lateralization of facial muscles below the eye?

contralateral (one side via opposite side)

where does the CN VII BM leave the brainstem?

internal acoustic meatus, stylomastoid foramen

what is the parotid plexus?

divides CN VII into 5 branches after coming out of skull

what are the 5 branches of CN VII BM from the parotid plexus?

• temporal nerve

• zygomatic nerve

• buccal nerve

• mandibular nerve

• cervical nerve

which is the only bilateral nerve of the parotid plexus?

temporal nerve

how is the parotid plexus arranged?

with redundany like circle of willis

which muscles does the temporal nerve innervate?

frontalis, corrugator supercilii, orbicularis oculi, procerus (think above eyes)

which muscles does the zygomatic nerve innervate?

orbicularis oculi, procerus, nasalis, depressor septi nasi, levator labii superioris alaeque nasi, levator labii superioris, levator anguli oris, zygomaticus major and minor, risorius (think below eyes above mouth)

which muscles does the buccal nerve innervate?

depressor septi nasi, nasalis, levator labii superioris alaeque nasi, levator labii superioris, levator anguli oris, zygomaticus major and minor, risorius, buccinator, orbicularis oris, depressor anguli oris, depressor labii inferioris (think mouth)

which muscles does the mandibular nerve innervate?

orbicularis oris, depressor anguli oris, depressor labii inferioris, mentalis (think below lips, chin)

which muscles does the cervical nerve innervate?

platysma (think neck)

what is the only gland of the head not innervated by CN VII VM?

the parotid gland

what are the major functions of CN VII VM?

• crying / tearing

• runny nose

• salivary flow (at rest)

where are CN VII VM brainstem nuclei?

superior salivatory nucleus in the pons

how does CN VII VM leave the pons?

through internal acoustic meatus and ganglion

what is the geniculate ganglion?

ganglion CN VII VM passes through when leaving skull

what happens to CN VII VM at geniculate ganglion?

divides into 2 fibre groups

what are the two fibre groups of CN VII VM made by the geniculate ganglion?

greater petrosal nerve and chorda tympani

how do greater petrosal nerve fibres leave the skull?

via foramen lacerum

what does greater petrosal nerve supply?

lacrimal and nasal glands, hard & soft palate

where does chorda tympani leave the skull?

via petrotympanic fissure