Medulla & CN IX, X, XI, XII

Question 1

Location of cell bodies of CN XII

Answer 1

Cell bodies of LMN are in the hypoglossal nucleus (near the midline & ventral to central canal of medulla)

Question 2

Where CN XII nerve fibers emerge

Answer 2

1. Axons pass inferolateral next to medial lemniscus and pyramids
2. Exit medulla as rootlets in the ventrolateral (preolivary) sulcus

Question 3

Corticobulbar fibers of CN XII

Answer 3

UMN of CN XII

Question 4

Corticobulbar fibers origin (CN XII)

Answer 4

Tongue region of the pre central gyrus (primary motor cortex)

Question 5

Corticobulbar fibers termination (CN XII)

Answer 5

Fibers descend w/ the corticospinal tract to the medulla, where most cross midline and synapse in the contralateral hypoglossal nucleus

Question 6

Sensory component of CN XII

Answer 6

Solitary nucleus (taste) and sensory trigeminal nucleus (bolus of food) sends info indirectly to hypoglossal nucleus by reticular formation

Question 7

Sensory component of CN XII function

Answer 7

Reflex pathway controlling tongue in swallowing, suckling and chewing

Question 8

LMN lesion of hypoglossal nerve

Answer 8

• paralysis and muscle wasting of intrinsic/extrinsic muscles on ipsilateral side
• protrusion of tongue, deviates to side of lesion
• dysarthria- difficulty eating and speaking

Question 9

UMN lesion of CN XII prior to crossing

Answer 9

• weakness of only extrinsic muscles (primarily genioglossus) on side contralateral to the lesion
• protrusion of tongue, deviates to opposite side of lesion

Question 10

Alternating hemiplegia

Answer 10

Combo of UMN and LMN signs, ipsilateral and contralateral presentation in different parts of the body

Question 11

CN X11 function

Answer 11

Hypoglossal nerve

Motor nerve that supplies the intrinsic/extrinsic muscles of the tongue

Question 12

Damaged structures from a stroke of a paramedical branch of the anterior spinal artery

Answer 12

Hypoglossal nerve fibers, adjacent pyramid, medial lemniscus and ventral trigeminothalamic tract

Question 13

Origin for cranial component of accessory nerve CN XI

Answer 13

LMN in the nucleus ambiguus that innervate a few of the laryngeal muscles

Question 14

Origin for spinal component of CN XI

Answer 14

Cell bodies located in the cervical levels of the spinal cord (dorsal to the ventral horn), innervate said SCM and traps

Question 15

Termination of spinal component of CN XI

Answer 15

Leave the spinal cord and ascend into cranial cavity to re-exit skull as accessory nerve

Question 16

Termination of cranial component of CN XI

Answer 16

Small # of fibers exit medulla w/ the vagus nerve

Question 17

UMN of CN XI tract/termination

Answer 17

Corticobulbar fibers descend w/ corticospinal fibers, decussate at pyramidal decussation and terminate in the cervical region (C2-4)

Question 18

Clinical test for CN XI

Answer 18

Patient is asked to turn head (SCM) or shrug shoulders (traps), cranial component indistinguishable from vagus nerve

Question 19

LMN origin for CN X- Vagus Nerve

Answer 19

Nucleus ambiguus, located in the reticular formation

Question 20

LMN for CN X- function

Answer 20

Innervates skeletal muscle of soft palate, larynx, pharynx, vocalis muscle

Question 21

Preganglionic parasympathetic cell body location (CN X)

Answer 21

Dorsal motor nucleus of X

Question 22

Preganglionic parasympathetic axon termination (CN X)

Answer 22

Exit medulla as rootlets of X and synapse on postganglionic neurons in visceral walls of glands, cardiac muscle and smooth muscle of the thorax and abdomen

Question 23

Sensory fibers CN X tract

Answer 23

Travel along solitary tract and end in solitary nucleus, sometimes the spinal trigeminal nucleus (pain for face)

Question 24

Sensory fibers CN X- function

Answer 24

Carry pain and pressure from pharynx, larynx, thorax and abdomen

Question 25

UMN of CN X

Answer 25

Corticobulbar fibers innervate the nucleus ambiguus bilaterally, so unilateral lesion would not be easily noticed

Question 26

Carotid sinus reflex afferent part

Answer 26

CN IX carries info from baroceptors in the carotid artery (near the bifurcation into internal and external carotid arteries) to the solitary nucleus, then to the dorsal motor nucleus of X

Question 27

Carotid sinus afferent part

Answer 27

CN X- reflex arc that innervate so the heart to slow HR

Question 28

Carotid body reflex- afferent limb

Answer 28

CN X- carries sensory info from chemoreceptors in lung bronchioles, synapse in medullary respiratory center (in reticular formation), to control breathing rhythm

Question 29

Carotid body reflex- efferent limb

Answer 29

CN X- Carries descending info to spinal cord levels controlling inspiration (intercostal and diaphragm)

Question 30

Cough, gag, vomiting reflexes

Answer 30

Sensory fibers from oral/nasal cavity (CN XI) or gut (CN X) is relayed to LMN in nucleus ambiguus and spinal cord, and Preganglionic parasympathetic in dorsal motor nucleus of X

Question 31

Unilateral lesion of LMN of CN X symptoms

Answer 31

difficulty swallowing, hoarseness (dysphonia), inability to raise the soft palate on ipsilateral side

Question 32

Lesions of preganglionic parasympathetic fibers of CN X symptoms

Answer 32

disruption of gut reflexes, hyperactivity can cause gastric acid secretion= ulcers

Question 33

Large bilateral lesions of the medullary reticular formation symptoms

Answer 33

disrupts normal breathing rhythms, reflex control of vascular resistance to blood flow and results in coma. Patients need life support

Question 34

LMN origin/function glossopharyngeal nerve CN IX

Answer 34

located in rostral end of nucleus ambiguus | innervates stylopharyngeus muscle

Question 35

Preganglionic parasympathetic origin CN IX

Answer 35

reticular formation

Question 36

Preganglionic parasympathetic tract CN IX

Answer 36

exit medulla to synapse on postganglionic neurons in otic ganglion

Question 37

Preganglionic parasympathetic function CN IX

Answer 37

innervates the parotid gland

Question 38

Sensory neurons- carotid sinus reflex- CN IX origin

Answer 38

afferent limb starts in the caudal part of the solitary nucleus

Question 39

Sensory neurons CN IX origin

Answer 39

sensory trigeminal nucleus, primarily spinal nucleus of V

Question 40

Sensory neurons CN IX function

Answer 40

- somatic sensations (touch,pressure,pain) from pharynx and post 1/3 of tongue (gag reflex) - taste sensation from post 1/3 of tongue to anterior solitary nucelus

Question 41

UMN CN IX

Answer 41

descends with corticobulbar system, synapses bilaterally on LMN in nucleus ambiguus

Question 42

CN IX reflexes

Answer 42

- carries afferent (sensory) limb for carotid sinus, gag, vomiting and swallowing - motor- swallowing, salivation, taste reflexes

Question 43

Unilateral lesions of CN IX symptoms

Answer 43

difficulty speaking, swallowing (less severe than CN X), visceral reflex impariments

Question 44

Diagnostic deficits CN X vs. CN IX

Answer 44

CN X- deviation of uvula | CN IX- loss of gag reflex to touching of pharynx