Lecture 10: Midbrain and Cranial Pons Flashcards
Which nerve(s) does the trochlear serve? What types of fibers?
cranial nerve IV, somatomotor fibers serving striated muscle (superior oblique)
What is unique about the trochlear nerve?
it exits dorsally
Describe the path of the trochlear nucleus? (midbrain)
just ventral and medial to the periaqueductal gray and ventures around the aqueduct dorsally and crosses superior and oblique
Name the nuclei of the trigeminal complex (4)
trigeminal motor nucleus, mesencephalic V, chief sensory trigeminal and the spinal trigeminal (stretch along whole length of the brainstem)
What types of fibers are in the trigeminal motor nucleus?
branchial motor (located more laterally) that supply striated muscle, muscles of mastication and tensor tympani
What types of fibers are found in the mesencephalic V? (midbrain)
(pseudo DR ganglion) somatosensory carrying unconscious proprioception of the jaw
What types of fibers are found in the chief sensory trigeminal? (where? seriously I have no idea)
somatosensory carrying touch sensation for the head and face
What types of fibers are found in the spinal trigeminal? (extends from the pons down to the cervical spinal cord)
somatosensory: pain and temp to the face and head
Discuss the path of alpha-beta, C/delta fibers and Ia,Ib and II and alpha motor neurons
alpha beta come in and synapse on the chief nucleus, cross the midline and ascend to the thalamus in the TTT (trigeminal thalamus tract) to the VPM; c, delta fibers come in and descend to the spinal nucleus, cross the midline and ascend to the thalamus; Ia,Ib and II come in and synapse on the mesencephalic nucleus before giving input to the motor nucleus V; motor nucleus V sends information via alpha motor neurons to the muscles of mastication
A lesion in the motor V might lead to what types of symptoms?
weakness in opening and closing the mouth, jaw deviates to the weak side and hyperacusis (acoustic)
CNV innervates tensor tympani for what purpose?
to dampens sounds (ie. from chewing)
Describe the jaw jerk reflex?
reflex loop created by the fibers synapsing on the mesencephalic nucleus V that feedback onto the motor nucleus that cause the movement of the muscles of mastication (reflexes increases with UMN lesion)
Where are motor nuclei located (generally) in relationship to the sensory nuclei?
from medial to lateral: somatomotor, branchiomotor, visceromotor, visceral sensory, somatosensory and special sensory
Describe the two nuclei of the oculomotor complex (in the upper midbrain).
serves cranial nerve III: oculomotor nucleus and the Edinger-Westphal nucleus
What type of fibers does the oculomotor nucleus serve?
somatomotor to the eye muscles traveling via the oculomotor nucleus
What type of fibers does the Edinger-Westphal nucleus serve?
autonomic- preganglionic parasympathetic to the iris and the cilia muscles (lens focus) which travel via the oculomotor
Where are the oculomotor nerves located relatively?
ventral to the brainstem, rostral to the pons near the midline: the tract travels ipsilaterally and ventrally from the nuclei until it exits the brainstem
What are symptoms of CNIII palsy?
closed lid (lavator palpebrae), deviated eye (diplopia-double vision) and dilated pupil (autonomics)
What is the medial longitudinal fascicles?
tract of vestibular and motor neurons for eye movement (? not positive on this)
How are the fibers of the spinal nucleus organized?
more caudal is represents the top/back of the head whereas the mouth/jaw is represented cranially; fibers from different cranial fibers enter along the descending pathways of the spinal nucleus; also more caudal signal is more localized pain
Describe the type of fibers in the abducens nucleus?
somatic motor that serves the extrinsic eye muscles via the abducens nerve (VI) as well as interneurons that help to coordinate eye movements (this tract crosses the midline)
What is significant about the tracts of the abducens
one tract says ipsilateral and one goes contralateral which is uniquely suited to control two different eyes to focus on a stimulus (coordinated eye movements)
What types of fibers does the cerebral peduncle contain?
Fibers traveling down from the cerebrum: corticopontine, coricospinal and corticobulbar
Describe the type of fibers from the facial nucleus and what they innervate. (caudal pons) AKA motor nucleus VII
branchial motor to striated muscle for facial expression
Describe the type of fibers from the superior salivary nucleus and what they innervate.
visceromotor (autonomic) to the submandibular, sublingual and lacrimal glands
Describe the fibers coming from the spinal nucleus V and what they innervate.
somatosensory of pain/temperature from the ear, and face
Describe the fibers coming from the nucleus of the solitary tract and what they innervate.
visceral sensory: taste to the anterior ⅔ parts of the tongue
Name the types of fibers that CN VII carries (4) and where they go.
the facial nerve contains branchio motor to LMN in the face and middle ear (motor root), pregangionics to the superior salivary and lacrimal glands (intermediate root) and visceral-tatse to anterior ⅔ tongue and somatosensory pain/temp- ear (sensory geniculate ganglion)
Describe the path of the facial nucleus (motor VII)
motor nucleus of VII sits just lateral and anterior to the superior olive in the caudal pons and heads medially and anteriorly to wrap around the nucleus of the abducens and heads out of the lateral brainstem
Describe the symptoms of a VII lesion
ispislateral symptoms including: face sags (muscles of facial expression), cannont close eye (obicularis oculi) and hyperacusis (stapedius)
Corticobulbars carry cortical input to facial nucleus and synapse on the upper and lower motor VII nuclei, what are the symptoms of a lesion of either
the top receives synapse unilaterally, so a lesion to one side is unlikely to cause problems but the lower nucleus receives synapse only from the contralateral side and if this is damaged, it can lead to lower face problems without affect of the upper face
Dampening of the stapedius is controlled by what nerve?
VII (facial)
