Term
| why is the medulla so important? |
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Definition
| it contains CN 9, 10, 11, 12 - the final control of life (ability to breathe and regulate heartbeat) - therefore it is very vulnerable to compression. |
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Term
| how are CN9 (glossopharyngeal) and 10 (vagus) tested? |
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Definition
| both are tested w/the gag reflex - but saying "ah" separately tests CN 10 |
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Term
| how is CN 11 (spinal accessory nerve) tested? |
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Definition
| lift shoulders and turn head |
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Term
| how is CN 12 (hypoglossal nerve) tested? |
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Definition
| tongue movement - stick out tongue, should come out straight. |
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Term
| how do CN 9, 10, 11, 12 come out of the medulla? |
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Definition
| CN 9, 10, 11 come laterally and inferior in successive order from the medulla. CN 9+10 are between the olive and the inferior cerebellar peduncle. CN 11 projects from the spinal cord (but does traffic through the jugular foramen with CN9 and CN10). CN 12 comes more medially and anteriorly from the same level as CN 9 (inferior to the pyramid, above the olive). |
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Term
| what are the 3 sensory nuclei in the medulla? what CN are involved w/which? (know these) |
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Definition
| trigeminal (CN 9, 10 - most lateral), solitarius - *very important for life, controls sensation of heart rate, CO2/O2, and pH levels (CN 9, 10 - most medial and inferior), and gustatory-solitarius - posterior 1/3 of the tongue (CN 9 right on top of the solitarius). |
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Term
| what are the 4 motor nuclei in the brainstem? |
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Definition
| hypoglossal (CN 12 - most medial), ambiguus (CN9, 10, 11 - most lateral and superior), dorsal vagal - parasympathetic (CN 10 - in between), and inferior salivary - parasympathetic to parotid gland (CN 9 - right above the dorsal vagal) |
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Term
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Definition
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Term
| what are the 5 cranial nuclei associated w/CN9? |
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Definition
| sensory: trigeminal (tonsil, external ear, internal tympanic membrane, pharynx), *solitarius (subconscious carotid sinus+body), gustatory (posterior 1/3 tongue). motor: ambiguus (stylopharyngeus - helps w/swallowing) and inferior salivatory (parasympathetics to the parotid). |
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Term
| what characterizes the general sensory (pain, touch, temperature) pathways of CN9? |
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Definition
| sensory information from the tonsil, external ear, internal tympanic membrane, pharynx, and posterior 1/3 of tongue all project to the inferior glossopharyngeal ganglion and then to the ipsilateral trigeminal nucleus and from there to the *contralateral (ventroposterior) thalamus and cortex. |
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Term
| what characterizes the visceral sensory (unconscious) pathway of CN9? |
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Definition
| sensory information from the carotid body and sinus (at bifurcation of the carotid artery) is sent to the inferior glossopharyngeal ganglion to the caudal solitarius nucleus, from which there are bilateral projections to the hypothalamus and to the RAS (provide feedback). there is a reflex arc here which also communicates w/CN 10. |
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Term
| what does the carotid body do? carotid sinus? |
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Definition
| carotid body: performs as a chemoreceptor - monitoring O2 tension in blood, CO2, and pH. carotid sinus: baroreceptor which monitors arterial blood pressure. |
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Term
| what characterizes the special sensory (taste) pathway of CN9? |
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Definition
| taste sensory information is sent from the posterior 1/3 of the tongue to the inferior glossopharyngeal ganglion to the gustatory nucleus and to the **ipsilateral thalamus and cortex. |
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Term
| what characterizes the general motor pathway of CN9? |
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Definition
| corticobulbar input projects from each hemisphere bilaterally to each nucleus ambiguus (UMN lesion would not be noticed in this muscle because of bilateral contribution from contralateral side). then from each ambiguus to each stylopharyngeus, which elevates the pharynx during swallowing and speech (LMN lesion would be noticeable on the side of the lesion). |
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Term
| what characterizes the visceral motor (parasympathetic efferent) pathway of CN9? |
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Definition
| ipsilaterally from the limbic system to the hypothalamus to the inferior salivatory nucleus to the parotid gland. |
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Term
| what is glossopharyngeal neuralgia? |
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Definition
| sharp/stabbing pulses of pain in the back of the throat/tongue/tonsils/middle ear which last a few sec - min. triggered by chewing, coughing, laughing, speaking, or swallowing. this is caused by blood vessels pressing down on the glossopharyngeal nerve, growths at the base of the skull, tumors/infections and idiopathic. tx: anticonvulsants (carbamazepine or gabapentin) or sx (nerve resection, tractotomy, microvascular decompression). |
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Term
| what are the 4 cranial nuclei associated w/CN10? |
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Definition
| sensory: trigeminal and solitarius. motor: ambiguus and dorsal vagal (parasympathetic nucleus) |
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Term
| what characterizes the general sensory (pain, touch, temperature) pathways of CN10? |
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Definition
| sensory information from the posterior meninges, concha, skin at the back of the ear and external acoustic meatus, part of the external surface of the tympanic membrane, the pharynx and larynx to the superior vagal ganglion to trigeminal nucleus to the *contralateral thalamus and cortex (gag reflex). |
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Term
| what characterizes the visceral sensory (unconscious) pathway of CN9? |
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Definition
| sensory information from the larynx, caudal trachea, esophagus, thoracic, abdominal viscera, baroreceptors (stretch) receptors in the aortic arch and chemoreceptors (pO2) is sent to the nucleus solitarius (cardiorespiratory center). therefore a unilateral lesion of the nucleus solitarius will not be fatal, but a bilateral lesion will lead to cardiac/respiratory failure (act fast if there is swelling in this area). |
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Term
| what does the reflex arc between the nucleus solitarius and dorsal motor vagal nucleus allow? |
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Definition
| an immediate response between the sensory and parasympathetic limbs of the vagus via bilateral connections to the RAS and hypothalamus |
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Term
| what characterizes the visceral motor (parasympathetic efferent) pathway of CN10? (there are 2) |
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Definition
| dorsal vagal motor nucleus -> smooth muscle/glands of the pharynx, larynx, and thoracic/abdominal viscera (stimulates increased bronchiolar secretions/constriction and stimulates increased secretions/motility) AND nucleus ambiguus -> cardiac muscle (slows down heart rate) |
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Term
| what characterizes the general motor pathway of CN10? |
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Definition
| nucleus ambiguus bilaterally -> superior/middle/inferior constrictors, levator palati, salpingopharyngeus, palatopharyngeus, palatoglossus (tongue), via the pharyngeal plexus and to the cricothyroid and intrinsic muscles of the larynx. (UMN lesions should not be as noticeable due to bilateral innervation from nucleus ambiguus). |
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Term
| how is a CN9 lesion differentiated from a CN10 lesion? |
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Definition
| look for uvular deviation while having the pt say "ah" and if it deviates = CN10 involvement (unilateral paresis of the superior pharyngeal constrictor). deviation of the uvula to one side implies a lower motor lesion of the vagus nerve contralateral to the side the uvula is deviating to (will also look atrophied if it has been going on for a while). an upper motor neuron vagus nerve lesion will present with the uvula deviating toward the side of the lesion. |
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Term
| how does the gag reflex work? |
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Definition
| sensory input from CN9 (posterior 1/3 of tongue) goes to the trigeminal nucleus, which then synapses (via interneuronal neuron) on the nucleus ambiguus which sends efferent signals to muscles in the pharynx, larynx, and tongue = gag. |
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Term
| what characterizes the swallowing reflex? |
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Definition
| sensory input from CN9 (posterior 1/3 of tongue) goes to the trigeminal nucleus, which then synapses (via interneuronal swallowing center [medullary reticular formation]) on the nucleus ambiguus which sends efferent signals to muscles in the pharynx, larynx, and tongue = start of peristalsis and inhibition of pharyngeal constrictor muscles. |
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Term
| what characterizes the vomiting reflex? |
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Definition
| similar to the gag reflex, or the opposite of the swallowing reflex, the signal for vomiting (reverse peristalsis) comes from the vomiting center in the medullary region and involves CN10. sources of stimulation include: GI tract irritation, gag reflex, area postrema (foreign substance in blood/CSF), vestibular apparatus, and the cerebral cortex (unpleasant sights/odors). |
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Term
| what characterizes the general motor pathway of CN11? |
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Definition
| the SCM has *ipsilateral projections from the corticospinal tract to the accessory spinal nucleus in the spinal cord and the trapezius has *contralateral projections to the accessory spinal nucleus in the spinal cord. even though the innervation pathways are different, R cortex LMNs will still cause the action to occur on the L side (R SCM contracts, head moves L and L trapezius contracts, L shoulder elevates) the innervations going out from the accessory spinal nucleus go up through the foramen magnum and then out through the jugular foramen on each side. |
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Term
| what are the classic symptoms associated w/compression of CN9,10,11 from a tumor? |
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Definition
| loss of gag reflex, whooshing sound (close to tympanic membrane) and a hoarse voice (vagus innervations of laryngeal muscles). |
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Term
| what characterizes the general motor pathway of CN12? testing? |
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Definition
| there is bilateral projections to all the tongue muscles (styloglossus, hyoglossus) through the hypoglossal nucleus, except for the genioglossus which is contralaterally innervated. this means the w/an UMN lesion, the tongue deviates toward the side opposite the lesion, but w/a LMN lesion, the tongue deviates toward the same side as the lesion (and ipsilateral side of tongue appears atrophied and has fasciculations if an older lesion). |
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