Medulla Flashcards
while cranial nerves can be found at some location within the medulla
8-12
closed medulla
-location
C1 to the caudal end of the 4th ventricle
nuclei within the closed medulla
inferior olivary nucleus or complex nucleus cuneatus nucleus gracilis hypoglassal nucleus spinal trigeminal nucleus (spinal nucleus of V)
tracts within the closed medulla
pyramids spinothalamic tracts (spinal lemniscus) ventral trigeminothalamic tract fasciculus cuneatus fasciculus gracilis medial longitudinal fasciculus (medial vestibulospinal tract) lateral vestibulospinal tract medial lemniscus internal arcuate fibers spinal trigeminal tract dorsal spinocerebellar tract hypoglossal nerve fibers
open medulla
-location
caudal end of 4th ventricle to the pontomedullary junction
nuclei within the open medulla
inferior olivary nucleus spinal nucleus of V hypoglossal nucleus dorsal motor nucleus of the Vagus nucleus ambiguus vestibular nuclei dorsal cochlear nucleus ventral cochlear nucleus
dorsal motor nucleus of the
Vagus
-sympathetic or parasympathetic
parasympathetic
what is within nucleus ambiguus
LMNs for CN IX and X
tracts within the open medulla
pyramids medial lemniscus hypoglossal nerve fibers ventral trigeminothalamic tract medial vestibulospinal tract (MLF) medial longitudinal fasciculus (MLF) lateral vestibulospinal tract inferior cerebellar peduncle olivocerebellar fibers lateral spinothalamic tract spinal trigeminal tract
CN XII
-function
motor nerve
supplies both intrinsic and extrinsic muscles of the tongue
CN XII
-LMN cell body location
hypoglossal nucleus
-near midline of medulla (ventral to the central or 4th ventricule)
CN XII
-LMN axon location
pass inferolateral to the medial lemniscus and pyramids
exit medulla as rootlets in the ventrolateral (preolivary) sulcus, adjacent to the pyramids
what comes out of the preolivary sulcus
CN XII fibers
CN XII UMNs
- name
- arise from…
- descend with _____ to ____
- synapse where?
corticobulbar fibers
arise from tongue region of precentral gyrus (primary motor cortex)
descend with the corticospinal tract to the medulla
most fibers cross midline in medulla and synapse in the contralateral hypoglossal nucleus
hypoglossal nucleus
- receives _____ sensory information from _____
- how does it receive this information
- this reflex pathway controlling the tongue is involved in…
receives indirect sensory information from solitary nucleus and sensory trigeminal nuclei
receives information via multisynaptic connections in the reticular formation
reflex pathway involved in swallowing, suckling, and chewing
solitary nucleus
-function in relation to CN XII
taste
sensory trigeminal nuclei
-function in relation to CN XII
bolus of food in the oral cavity
LMN lesion of the hypoglossal nerve or nucleus
- results in…
- clinical signs
results in paralysis and muscle wasting of both the intrinsic and extrinsic muscles of the ipsilateral side
clinical signs
-upon protrusion of the tongue, it deviates toward the side of the lesion due to unopposed action of the intact contralateral genioglossus muscle
-patients have difficulty with eating and speaking (dysarthria)
UMN lesion of the hypoglossal nerve
- where does it occur
- results in…
occurs at a level prior to the cross
results in weakness of only the extrinsic muscles (primarily genioglossus) on the side contralateral to the site of the lesion
which way will the tongue deviate if a UMN for CN XII is injured?
contralateral side
stroke of paramedian branch of anterior spinal artery may result in damage to…
hypoglossal nerve fibers
adjacent pyramid
medial lemniscus
ventral trigeminothalamic tract
stroke of paramedian branch of anterior spinal artery will produce what symptoms?
LMN symptom (ipilateral) UMN symptoms involving the pyramid (contralateral)
the combination of LMN and UMN signs that are seen on opposite sides of the neuraxis with injury to the paramedian branch of the anterior spinal artery occur where…
-this combo of Sx is called…
occur where a motor cranial nerve exits along the midline adjacent to the descending corticospinal fibers
combo of Sx is called an alternating hemiplegis
CN XI
- location of LMNs
- functions of LMNs in each location
nucleus ambiguus
-innervate a few of the laryngeal muscles (cranial component)
cervical levels of spinal cord (dorsal to ventral horn)
-innervate SCN and trapezius
CN XI
-axons of spinal component: location
leave spinal cord and ascend into cranial cavity through foramen magnus to re-exit the skull as the accessory nerve through the jugular foramen
CN XI
-axons of the cranial component: location of the ones that leave the cranium
small number exit medulla along with vagus nerve
CN XI UMNs
- descend with
- decussate at…
- terminate where
descend with corticospinal fibers
decussate at the pyramidal decussation
terminate in the cervical region (C2-4)
CN XI
-clinical testing
turn head (SCM) shrug shoulders (trap) cranial component is indistinguishable from vagus nerve
CN X
-LMN location and function
located in nucleus ambiguus
-innervate skeletal muscles of the soft palate, larynx and pharynx, including vocalis muscle (true vocal folds)
nucleus ambiguus
- location
- contains…
located in reticular formation -not easily identified contains -LMNs for CN X and IX -LMNs for cranial part of CN XI
CN X: preganglionic parasympathetic cell bodies
-location
dorsal motor nucleus of X
CN X: preganglionic parasympathetic axons
- location
- synapse…
exit medulla as rootlets of X
synapse on postganglionic neurons in visceral walls of glands, cardiac muscle and smooth muscle of the thorax and abdomen
CN X sensory fibers
- travel along
- end in
- function
- some fibers may enter…
travel along solitary tract to end in solitary nucleus
this component carries pain and pressure from pharynx, larynx, and thorax and abdomen
some of these fibers may enter spinal trigeminal nucleus (pain of the face)
CN X UMNs
- innervate…
- -clinical implication
innervate nucleus ambiguus bilaterally
therefore, a unilateral lesion of the UMN would not be easily noticed
important reflexes that are mediated by parts of the vagus nerve
carotid sinus reflex
carotid body reflex
cough, gag, and vomiting reflexes
carotid sinus reflex
-CN X carries what part of the reflex
carries the efferent part of this reflex arc to the heart
carotid sinus reflex: afferent limb
- originates from…
- afferent info carried by _____ to _____, then relayed to _____
originates from barareceptors along the carotid artery near the bifurcation into internal and external carotid arteries
carried by fibers of CN IX to the solitary nucleus, then relayed to the dorsal motor nucleus of X
carotid sinus reflex: efferent limb function
innervates heart to slow heart rate
carotid body reflex: function
helps control breathing rhythm
carotid body reflex: role of CN X
carries one sensory (afferent) component, the chemoreceptor sensation from lung bronchioles, which synapse in the medullary respiratory center (area in the reticular formation)
carotid body reflex: efferent limb is via…
via descending information to spinal cord levels controlling inspiration (intercostals and diaphragm)
cough, gag and vomiting reflexes
-involves sensory fibers from…
oral/nasal cavity (CN IX)
OR
the gut (CN X)
cough, gag and vomiting reflexes
-sensory information relayed to…
appropriate LMNs in
- nucleus ambiguus and spinal cord
- preganglionic parasympathetics in dorsal motor nucleus of X
will as lesion of CN X result in sensory or motor deficits, or both
can result in both
unilateral lesions of LMNs of CN X
-results in…
difficulty in swallowing
hoarseness (dysphonia)
inability to raise the soft palate on ipsilateral side
lesions of the preganglionic parasympathetic fibers of CN X
- cause disruption of some _____ reflexes
- less important for diagnosis of lesion location than deficits associated with…
cause disruption of some gut reflexes
less important for diagnosis of lesion location than are deficits asosciated with somatomotor LMN component
preganglionic parasympathetic fibers of CN X
-hyperactivity can cause
excess gastric acid secretion = ulcers
large bilateral lesion of the medullary reticular formation
- what can happen?
- prognosis
can disrupt normal breathing rhythms and reflex control of vascular resistance to blood flow
-can result in coma
poor prognosis; may need life support
CN IX LMNs
- control
- location
LMNs for stylopharyngeus muscle
located in rostral end of Nucleus Ambiguus
which CNs have LMNs in the Nucleus ambiguus
IX, X, XI
CN IX preganglionic parasympathetic neurons
- cell body location
- axon location and synapse
- -function to…
cell body
-reticular formation
axons
-exit medulla to synapse on postganglionic neurons for innervation of parotid gland
CN IX sensory neurons: central processes
- synapse in…
- carry…
synapse in caudal part of solitary nucleus
carries the afferent limb of the carotid sinus reflexes
CN IX sensory neurons central processes
- also synapses in…?
- carries
synapse in sensory trigeminal nuclei
-primarily spinal nucleus of V
carries somatic sensation (touch, pressure, pain) from pharynx and posterior 1/3 of tongue (gag reflex)
also carries taste sensation from posterior 1/3 of tongue (mainly bitter sensation) to rostral part of solitary nucleus
CN IX cortical control (UMN)
- descends as part of…
- synapse location
descends as part of corticobulbar system
synapses bilaterally on LMNs in nucleus ambiguus
CN IX reflex involvement
carries afferent (sensory) limb for several reflexes who efferent limb is carried by CN X, XII, and/or spinal cord LMN's these reflexes include carotid sinus, gag, vomiting, and swallowing reflexes
CN IX motor components
-participate in which reflexes
participate in swallowing and salivation - taste reflexes
unilateral lesions of CN IX
- can produce…
- severity compared to CN X lesions
can produce difficulty with speech and swallowing
deficits less severe than with CN X lesions
can affect some visceral reflexes, similar to CN X
what are the most diagnostic deficits which distinguish bewteen IX and X lesions
loss of gag reflex to touching the pharynx
-CN IX, afferent limb)
deviation of uvula
-CN X, efferent limb)
where is the majority of the cochlear component of CN VIII found?
pons
