Cranial Nerves_ Medulla Flashcards
Closed medulla (nuclei) –>
- caudal end of IVth ventricle
- Inferior olivary nucleus or complex
- Nucleus cuneatus, n. gracilis
- Hypoglossal nucleus
- Spinal Trigeminal Nucleus (Spinal nucleus of V)
Close medulla (tracts) :
- pyramids •medial lemniscus
- spinothalamic tracts (spinal lemniscus)
- internal arcuate fibers
- ventral trigeminothalamic tract • spinal trigeminal tract
- fasciculus cuneatus, f. gracilis • dorsal spinocerebellar tract
- medial longitudinal fasciculus (MLF)
- cuneocerebellar tract [medial vestibulospinal tract]
- lat. vestibulospinal tract • hypoglossal nerve fibers
Open medulla (nuclei) : caudal end of IVth ventricle –>
- pontomedullary junction
- inferior olivary nucleus
- spinal nucleus of V • hypoglossal nucleus
- dorsal motor nucleus of the • • • Vagus (parasympathetic)
- nucleus ambiguus (lower motor neurons for CN IX and X)
- vestibular nuclei (medial and inferior)
- dorsal, ventral cochlear nucleus
Open medulla tracts:
- Pyramids lat. vestibulospinal tract
- medial lemniscus
- inferior cerebellar peduncle
- hypoglossal nerve fibers • olivocerebellar fibers
- ventral trigeminothalamic tract • lateral spinothalamic tract
- med. vestibulospinal tract (MLF) • spinal tract of V • medial longitudinal fasciculus
Hypoglossal nerve (CN XII) =
is a motor nerve that supplies both the intrinsic and extrinsic muscles of the tongue.
The cell bodies of the lower motor neurons are in the hypoglossal nucleus, located near the __________ of the medulla (ventral to the central canal or ______________).
midline
4th ventricle
The axons pass inferolateral next to the _______________________________ to exit the medulla as rootlets in the ventrolateral (____________) sulcus.
medial lemniscus and pyramid
preolivary
Corticobulbar fibers (cortical control; upper motor neurons) arise from the _________ region of the precentral gyrus (Primary motor cortex) and descend with the corticospinal tract to the medulla where most of the fibers cross the midline and synapse in the _______________________ hypoglossal nucleus
tongue
contralateral
The _______________ nucleus receives indirect sensory information from solitary nucleus (taste) and sensory trigeminal nuclei (bolus of food in the oral cavity) by way of multisynaptic connections in the ____________________. This reflex pathway controlling the tongue is involved in swallowing, suckling and chewing.
hypoglossal
reticular formation
Clinically, a lower motor neuron lesion of the hypoglossal nerve or nucleus results in paralysis and muscle wasting of both the intrinsic and extrinsic muscles on the __________________ side.
ipsilateral
Upon protrusion of the tongue, it deviates toward the side of the lesion due to the unopposed action of the intact _________________________ muscle.
contralateral genioglossus
What is dysarthria.
Patients have difficulty with eating and speaking
An upper motor neuron lesion that occurs at a level prior to the crossing, 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 upon voluntary protrusion in this case?
???
The _________________ nerve is important in identifying the level of lesions (strokes) in the medulla.
hypoglossal
A stroke of a paramedian branch of the anterior spinal artery may result in combinations of damage to the:
hypoglossal nerve fibers
adjacent pyramid
medial lemniscus and ventral trigeminothalamic tract
The result (of a stroke of a paramedian branch of the anterior spinal artery) is a lower motor neuron symptom involving the tongue (deficit is noted ipsilateral or contralateral?) and upper motor neuron symptoms involving the ____________ (deficit is noted ipsilateral or contralateral?).
tongue
pyramid
What sensory deficits may also accompany the motor signs in this example?
???
This type of combination of lower and upper motor neuron signs that are demonstrated on opposite sides of the neuraxis occur where a motor cranial nerve exits along the:
This combination of symptoms is called an:
midline adjacent to the descending corticospinal fibers
alternating hemiplegia.
What cranial nerve(s) supply the somatosensory and taste components for the tongue?
trigeminal, facial, glossopharyngeal
Accessory nerve (CN XI) =
contains a few lower motor neurons in nucleus ambiguus that innervate a few of the laryngeal muscles (cranial component).
The cell bodies innervating the sternocleidomastoid and trapezius muscles (spinal component) are located in the cervical levels of the spinal cord (dorsal to the ventral horn). Axons of the spinal component leave the spinal cord and ascend into the cranial cavity to re exit the skull as the ______________ nerve. For the cranial component, a small number of fibers exit the medulla along with the _____________ nerve.
accessory
vagus
Upper motor neurons (corticobulbar fibers) descend with the corticospinal fibers, decussate at the _________________________ and terminate in the cervical region (___________).
pyramidal decussation
C2-4
Clinically, to test for involvement of the spinal part of CN XI the patient is asked to:
The cranial component is indistinguishable from the ___________ nerve.
turn the head (sternocleidomastoid) or shrug the shoulders (trapezius).
vagus
Vagus nerve (CN X)
has several functional components.
Vagus nerve (CN X) Lower motor neurons located in \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_innervate skeletal muscles of the soft palate, larynx and pharynx, including vocalis muscle (True vocal folds).
nucleus ambiguus
Vagus nerve (CN X) Nucleus ambiguus is located in the \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ and is not easily identified (a clue to its name). It contains lower motor neurons for CN \_\_\_ and \_\_\_ as well as for the cranial part of CN \_\_\_.
reticular formation
X, IX , XI
Vagus nerve (CN X) Preganglionic parasympathetic cell bodies are located primarily in the dorsal motor of \_\_\_\_\_\_\_\_\_\_\_\_\_. The axons exit the \_\_\_\_\_\_\_\_\_\_\_\_\_ as rootlets of X and synapse on postganglionic neurons in visceral walls of glands, cardiac muscle and smooth muscle of the thorax and abdomen.
nucleus of X
medulla
Vagus nerve (CN X) Sensory fibers travel along the solitary tract to end in the \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_. This component is carrying \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ from pharynx, larynx and thorax and abdomen. Some of these fibers may enter the spinal trigeminal nucleus (Remember, pain of the face).
solitary nucleus
pain and pressure
Vagus nerve (CN X) Upper motor neurons (corticobulbar) innervate the nucleus ambiguus \_\_\_\_\_\_\_\_\_\_\_\_\_ .
bilaterally
Therefore, a unilateral lesion of the upper motor neurons would not be easily noticed.
Vagus nerve (CN X) Several important reflexes =
are mediated (carried) via parts of the vagus nerve.
Carotid sinus reflex =
CN X carries the efferent part of this reflex arc to the heart.
Vagus nerve (CN X) The afferent limb originates from \_\_\_\_\_\_\_\_\_\_\_\_\_\_ along the carotid artery near the bifurcation into internal and external carotid arteries. The afferent information is carried by fibers of CN IX to the \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_, then relayed to the \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_. This efferent limb of the reflex arc innervates the heart to slow heart rate.
baroceptors
solitary nucleus
dorsal motor nucleus of X
Vagus nerve (CN X) Carotid body reflex = a complex reflex that uses CN X to carry \_\_\_\_\_\_\_\_\_\_\_\_ sensory (afferent) component, the \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ sensation from lung bronchioles, which synapse in the "medullary respiratory center" (an area in the reticular formation). This reflex helps control breathing rhythm. The efferent limb is via descending information to spinal cord levels controlling inspiration (intercostals and diaphragm).
one
chemoreceptor
Vagus nerve (CN X) Cough, gag and vomiting reflexes =
complex reflexes involving sensory fibers from oral/nasal cavity (CN IX) or the gut (CN X). Sensory information is relayed to appropriate lower motor neurons in nucleus ambiguus and spinal cord, and preganglionic parasympathetics in dorsal motor nucleus of X.
lesions of CN X result in _______________________________ deficits.
both sensory and motor
______________________ lesions of lower motor neurons in CN X results in difficulty in swallowing, hoarseness [dysphonia], inability to raise the soft palate on ______________________ side.
Unilateral
ipsilateral
Lesions of the preganglionic parasympathetic fibers of CN X cause disruption of some gut reflexes, but are less important for diagnosis of lesion location than are deficits associated with the ___________________________________.
somatomotor LMN component
Hyperactivity (excess firing) can cause excess gastric acid secretion =
ulcers.
Large ______________ lesions of the medullary reticular formation can disrupt normal ______________________ and reflex control of ___________________________ to blood flow and result in coma. Patients with this type of damage may need life support systems and have a poor prognosis.
bilateral
breathing rhythms
vascular resistance
Glossopharyngeal CN IX
Lower motor neurons for stylopharyngeus muscle; LMN’s located in rostral end of ____________________.
Nucleus Ambiguus
What other cranial nerves also have LMN’s in this nucleus?
???
Glossopharyngeal CN IX
Preganglionic parasympathetic neuron cell bodies located in reticular formation; axons exit medulla to synapse on postganglionic neurons in ______________________, which then innervates the ___________________.
otic ganglion
parotid gland
[Remember from anatomy that this component follows the auriculotemporal branch of V3]
Glossopharyngeal CN IX
Sensory neurons =
central processes synapse in the caudal part of the solitary nucleus; carries the afferent limb of the carotid sinus reflexes.
Glossopharyngeal CN IX
Central processes synapse in ________________________; primarily spinal nucleus of V; carries somatic sensations (touch pressure, pain) from pharynx and posterior 1/3 of tongue [Gag reflex]. This portion also carries _________ sensation from __________ 1/3 of tongue (mainly bitter sensation) to ______________ part of solitary nucleus.
sensory trigeminal nuclei
taste
posterior
anterior
Glossopharyngeal CN IX Cortical control (UMN) in cortex descends as part of corticobulbar system to synapse \_\_\_\_\_\_\_\_\_\_\_\_\_\_ on LMN's in nucleus ambiguus.
bilaterally
Glossopharyngeal CN IX
Reflexes - CN ________ carries the afferent (sensory) limb for several reflexes whose efferent limb is carried by _______________________, and/or spinal cord LMN’s. These include carotid sinus, gag, vomiting and swallowing reflexes. Also, the motor components of IX participate in swallowing and salivation -
CN IX
CN X, CN XII
taste reflexes.
______________ lesions of CN IX can produce difficulty with speech and swallowing but deficits are less severe than with CN X lesions. Some _____________ reflexes can be impaired as with CN X lesions.
Unilateral
visceral
The most diagnostic deficits which distinguish between IX and CN X lesions are:
loss of gag reflex to touching the pharynx (CN IX, afferent limb) compared to deviation of uvula (CN X, efferent limb).
