Lecture 12: Medulla Flashcards
What types of fibers and what nerves come from the nucleus ambiguus?
branchial motor that serve CN IX (stylopharyngeus which elevates the pharynx during swallowing) and the CN X to the palatal (veil palatini), pharyngeal and laryngeal muscles
Name the broad functions of the fibers leaving the nucleus ambiguus.
swallowing and speech (elevate palate for swallowing and speech as well as dilate the pharynx for swallowing
Describe the nerves coming from the nucleus ambiguus involved in the gag reflex
the sensory limb includes nerves IX and X via pain pathways (spinal tract and spinal nucleus V) and projects bilaterally; the motor limb synapse with sensory limb in the nucleus ambiguus and goes out to the pharyngeal constrictors
What effects will a lesion on the sensory limb (sensory nerve) of the gag reflex
cannot elicit response from the ipsi side but stimulation contra side can elicit a bilateral response
What effects will a lesion in the motor limb (motor innervation to muscle) of the gag reflex
no response on the ipsi side regardless of stimulation side, stimulation of either side elicits response on side contra to lesion
Describe the effect of a lesion in the nucleus ambiguus on the uvula
uvula deviates to the strong side (caused by weakness in the levitator veil palatini)
Describe the type of fibers coming from the hypoglossal nucleus and what they innervate. (medulla)
cranial nerve XII- hypoglossal- produces somatomortor that innervate the striated muscle of the tongue
Describe the path of fibers leaving the hypoglossal nucleus.
nucleus lies medial and posterior near to the 4th ventricle in the medulla, the descend ipsilaterally between the inferior olives and then exit anterior-lateral (between the pyramid and the inferior olive) to synapse with the LMN of the tongue
How would you find a lesion on the hypoglossal nerve?
have patient stick out tongue, if there is a lesion, the tongue will deviate toward the weak side (muscles affect push the tongue forward and medially); note that LMN neuron lesion will also cause atrophy BONUS: a lesion will also affect the functions of speaking, chewing, swallowing, and buccal cleaning
Describe the fibers of the accessory nucleus and what those fibers serve (cell bodies C1-C5/6 ventral horn)
branchial motor to striated muscles via the sternocleidomastoid and trapezius
Describe the pathway of fibers leaving the accessory nucleus.
cell body in the ventral horn exits laterally (NOT VIA VENTRAL ROOT) and ascends brainstem assembling and then descend to innervate sternocleidomastoid and trapezius
What are the actions of the sternocleidomastoid and the trapezius?
sternocleidomastoid turns head to the opposite side, trapezius partially elevates shoulders
