Cranial Nerves 4 Flashcards

1
Q

What do the cranial root of CN XI joining CN X become?

A

The special visceral efferent component from the nucleus ambiguus

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2
Q

Describe the course of CN IX, X and the cranial root of XI.

A

Emerge from the medulla oblongata and pass through the jugular foramen

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3
Q

Describe the course of the spinal root of CN XI.

A

Emerges from the superior spinal cord, ascends to the skull via the foramen magnum before passing through the jugular foramen.

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4
Q

Describe the course of CN XII.

A

Emerges from the medulla oblongata and passes through the hypoglossal canal (anterior condylar canal)

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5
Q

What is the function of the glossopharyngeal nerve (CN IX)?

A

PRIMARY:
General Sensation: (Posterior 1/3) Tongue & Oropharynx (general somatic afferent)

ADDITIONAL:
Parasympathetic (general visceral efferent)
Posterior 1/3 Taste/Gustation (special visceral afferent)
Carotid Body & Sinus (general visceral afferent)

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6
Q

What is the function of the vagus nerve (CN X)?

A

PRIMARY:
General Sensation: Pharynx & Larynx (general somatic afferent) Parasympathetic Heart, Lungs, GI Tract (general visceral efferent)

ADDITIONAL:
Motor to Pharynx & Larynx via Cranial Root of XI (special visceral efferent) Epiglottis Taste/Gustation (special visceral afferent)
Aortic Arch & Bodies (general visceral afferent)

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7
Q

What is the function of the hypoglossal nerve (CN XII)

A

Motor: Tongue (general somatic efferent)

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8
Q

What are the nuclei of CN IX?

A
  • CN IX inferior salivatory nucleus with parasympathetic secretomotor to parotid gland (in the pons)
  • CN IX & X (also CN VII) solitary nucleus for taste and visceral sensation (in the medulla)
  • CN IX & X nucleus ambiguus to striated muscles of pharynx and larynx (in the medulla)
  • Spinal nucleus of CN V also receiving general sensation from CN IX & X (in the medulla)
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9
Q

What are the nuclei of CN X?

A
  • CN IX & X (also CN VII) solitary nucleus for taste & visceral sensation (in the medulla)
  • CN IX & X nucleus ambiguus to striated muscles of pharynx & larynx (in the medulla)
  • Spinal nucleus of CN V also receiving general sensation from CN IX and X (in the medulla)
  • CN X dorsal nucleus with parasympathetic to heart, lungs and GI tract (in the medulla)
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10
Q

What are the nuclei of CN XII?

A
  • CN XII hypoglossal nucleus for motor to tongue (in the medulla)
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11
Q

Describe the course and distribution of CN XI spinal root?

A

Spinal root of XI arising from C1 to C5, going through the jugular foramen, and crossing the posterior triangle of the neck supplies the sternocleidomastoid & trapezius muscles

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12
Q

Describe the course and distribution of CN IX?

A
  • CN IX emerging from the jugular foramen, adjacent to the wall of the pharynx, with CN X & XI
  • General visceral afferent (sensory) supply from the carotid body (chemoreceptors) & carotid sinus (baroreceptors) for reflex cardiovascular control
  • Tympanic branch of CN IX to middle ear (general sensation), tympanic membrane & mastoid air cells. (also contains preganglionic parasymp. neurons for the parotid gland that leave the plexus in the lesser petrosal nerve)
  • Taste fibres from posterior 1/3 of tongue (general sensation to posterior 1/3 of tongue, tonsils and oropharynx)
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13
Q

Describe the course of the lesser petrosal nerve.

A

Lesser Petrosal nerve escapes from the middle ear & lies on the surface of the petrous temporal bone in the middle cranial fossa before emerging through the foramen ovale

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14
Q

Describe the innervation of the parotid gland.

A
  • Tympanic branch of CN IX carrying preganglionic parasympathetics from the inferior salivatory nucleus to the tympanic plexus (also receiving somatic sensation via CN IX)
  • Gives off lesser petrosal nerve passing through foramen ovale & synapsing in otic ganglion (suspended from CN V3)
  • Postganglionic fibres passing to the auriculotemporal nerve that sends a branch to the parotid gland
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15
Q

What is the distribution of the vagus nerve (CN X)?

A
  • General sensation from the laryngopharynx & larynx
  • General sensation from deep auricle & parts of the external acoustic meatus
  • General visceral sensory afferents from blood vessels for control of CVS plus afferents from the heart, lungs & GI tract
  • Taste from the vallecula & epiglottis
  • Motor supply to the striated muscles of the pharynx & larynx derived from 4th & 6th pharyngeal arches via Cranial Root of XI
  • Parasympathetic supply to the heart, lungs & GI tract as far as 2/3 along the transverse colon
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16
Q

Apply the innervation of the pharynx?

A
  • The nerve supply to the pharynx is via the pharyngeal plexus that lies on the external pharyngeal wall (over middle constrictor) & receives branches of CN IX & X as well as cervical sympathetics
  • The plexus supplies the pharyngeal musculature (plus levator palati, palatopharyngeus & palatoglossus) as well as sensation to the underlying mucous membrane
17
Q

What is the sensory innervation of the pharynx?

A
  • Oropharynx, palatine tonsil, inferior aspect of soft palate &posterior 1/3 of tongue supplied by CN IX
    Laryngopharynx, vallecula & epiglottis supplied by CN X
18
Q

What is the motor innervation of the pharynx?

A
  • Parasympathetic secretomotor by CN X directly & pterygopalatine ganglion (CN VII) via CN V2
  • Musculature by CN X except stylopharyngeus that is by CN IX
19
Q

Describe the gag reflex course.

A
  • Sensory information Brough in by CN IX
  • Synapses in the nucleus solitaires
  • Interneuron then synapses in the nucleus ambiguus which sends motor branches from CN X to the Pharynx
20
Q

Describe the sneezing and coughing reflexes.

A

Irritants are detected by CN V2 which synapses in trigeminal sensory nucleus
Interneuron then passes to the nucleus ambiguus where it synapses at the nucleus ambiguus and sends motor branches from CN IX and X to the pharynx

21
Q

Describe the course and distribution of CN XII.

A
  1. CN XII passes through the hypoglossal canal
  2. CN XII descends to the neck passing lateral to the internal &external carotid arteries associated with a loop of cervical nerves that supply the strap muscles of the neck
  3. CN XII enters the oral cavity under the tongue between the mylohyoid & hyoglossus to supply all tongue muscles except the palatoglossus that is supplied by CN X via the pharyngeal plexus
22
Q

What occurs if there is an injury to CN XII?

A

there is ipsilateral tongue weakness with deviation to the side of the lesion

23
Q

Describe the innervation of the tongue.

A
  • Anterior 2/3 via lingual nerve (CN V3) for general sensation with taste from the nervus intermedius of CN VIII (chorda tympani hitch-hiking with the lingual nerve)
  • Posterior 1/3 is by CN IX for both general sensation & taste
  • Motor supply to all muscles is by CN XII except palatoglossus that is by CN X via the pharyngeal plexus
24
Q

Describe the innervation of the larynx.

A
  • CN X sends the superior laryngeal nerve that passes with the superior thyroid artery until it divides into internal & external branches
  • Sensation of the larynx down to just above the vocal folds is by the internal laryngeal branch that is accompanied by the superior laryngeal artery from the superior thyroid artery
  • The cricothyroid is supplied by the external branch & this is the only intrinsic muscle of the larynx not supplied by the recurrent laryngeal nerve
  • The recurrent laryngeal branch of CN X passes inferior to the aortic arch on the left (close to the lung hilum) or the subclavian artery on the right & then ascends between the trachea & oesophagus to intermingle with branches of the inferior thyroid artery close to the thyroid gland before entering the larynx
  • The recurrent laryngeal nerve supplies all the intrinsic muscles of the larynx (except the cricothyroid) & provides sensation to the larynx below the vocal folds