Brainstem I Flashcards
Brainstem functions
- conduit for info to/from spinal and supraspinal levels
- origin of descending pathways (motor, pain)
- processes/integrates info
- centers for respiration, HR, BP, consciousness
- cranial n.=spinal n. (equivalent functions), and convey taste, hearing, equilibrium
- preganglionic parasympathetic neurons (thoracic and abd viscera, pupillary sphincter, salivation/ lacrimation)
- synthesis of NTs (CNS)
- critical functions = small region
Characteristics of SPINAL CORD LESIONS involving LONG TRACTS
- effects observed at level of lesion and below
- pain and temp loss side opposite of lesion
- weakness, position sense and vibration sense lost ipsilaterally
Characteristics of BRAINSTEM LESIONS
- lesions of 3 long tracts in brainstem –> contralateral deficits
- cranial nerve signs will reveal the level of the lesion in brainstem
- cranial nerve signs observed on the side of lesion
3 parts of the brainstem
medulla
pons
midbrain
____ a. –> supplies medulla
vertebral a. –> supplies medulla
____ a. –> supplies pons
basilar a. –> supplies pons
the basilar a. ends at the level of the ____, giving rise to the ____ a. –> which supplies the ____
the basilar a. ends at the level of the MIDBRAIN, giving rise to the POSTERIOR CEREBRAL a. –> which supplies the MIDBRAIN
The ventral surface of the brainstem contains
pyramids (corticospinal path decussation)
olives
cranial nerve rootlets of IX, X, XI. XII
midline bulge of medulla
pyramid
where corticospinal tract crosses
between pyramids and olive, CN __ exits
between pyramids and olive, CN XII exits
___ forms roof of fourth ventricle
___ forms floor of fourth ventricle
CEREBELLUM forms roof of fourth ventricle
MEDULLA/PONS forms floor of fourth ventricle
The dorsal surface of the brainstem contains
inferior/superior colliculus
inferior/middle/superior cerebellar peduncle
F. cuneatus/F. gracilis (dorsal column paths)
cuneate tubercle/gracile tubercle (surface elevations formed by second order neurons for dorsal column path which reside underneath)
reticular formation
central core of medulla,
pons and midbrain
controls…
respiration
BP
HR
medial lemniscus is formed by fibers leaving the
nucleus gracilis and nucleus cuneatus
becomes more horizontal and unites with spinothalamic path as you ascend through brainstem
medial medullary lesion
TRACTS LOST: Reticular Formation -respiration, BP, HR Medial Lemniscus -dorsal column pathway -position, vibration loss (contralateral) Corticospinal Tract -fine, distal movement (hemiparesis contralaterally)
CN SIGNS CN XII: Hypoglossal -ipsilateral tongue paralysis -fasiculations -protrusion causes tongue deviation TWD lesion
LMN send axons out to
striated m.
analogous to LMN in spinal cord, also receive input
motor cranial n. nuclei receive cortical input via ______
w/ the exception of…
motor cranial n. nuclei receive cortical input via CORTICOBULBAR PATHWAY
w/ the exception of CN NUCLEI INNERVATING EYE
corticobulbar pathway
UMN synapse on facian nucleus either bilaterally (upper face) or contralaterally (lower face) on motor nuclei of the brain stem
alar plate gives rise to
sensory neurons
basal plate gives rise to
motor neurons
motor nuclei are (medial/lateral) to sensory nuclei in the brainstem, and are separated by _______
motor nuclei are medial to sensory nuclei in the brainstem, and are separated by sulcus limitans
2 sets of nuclei that innervate striated muscle, which are most medial?
somatic motor nuclei (most medial)
somatosensory nuclei (most lateral)
which nuclei are adjacent to the sulcus limitans?
visceromotor (VM) viscerosensory (VS)
lateral strokes involve which nuclei?
pharyngeal motor (branchial motor)
medial strokes involve which nuclei?
somatic motor nuclei
columns of CN nuclei (midline to lateral)
somatic motor (hypoglossal)
branchial motor AKA pharyngeal (ambiguous - CN IX, X, XI)
visceral motor (dorsal X)
visceral sensory (solitarius)
somatosensory (spinal V)
social senses (vestibular, cochlear)
caudal medulla: motor decussation
on ventral aspect, the descending lateral corticospinal tract fibers and corticobulbar tract fibers from cortical UMNs decussate through the pyramids to the side they will be innervating
caudal medulla: sensory crossing
on the dorsal aspect, the ascending dorsal column fibers run in fasiculus gracilis and fasiculus cuneatus
synapse to their respective nuclei gracilis/cuneatus
second order neurons project fibers which decussate through the medial lemniscus on their way to the thalamus.
(CROSS SECTION LOOKS LIKE ARTIST PALETTE)
if there are fibers in medial lemniscus –> they are (ipsilateral/contralateral) to site of origin
if there are fibers in medial lemniscus –> they are CONTRALATERAL to site of origin
lesion will cause contralateral damage
lesion to nucleus gracilis or nucleus cuneatus –> (ipsilateral/contralateral) damage
lesion to nucleus gracilis or nucleus cuneatus –> (IPSILATERAL) damage
distinct feature of nucleus solitarius
found lateral to dorsal motor nucleus of CN X
has tract running through it
hypoglossal nucleus
innervates intrinsic/extrinsic m. of tongue
lesion of hypoglossal nucleus
- paralysis of tongue on side of lesion
- fasciculations - LMN sign
- upon protrusion, tongue deviates to side of lesion
nucleus ambiguus
innervates larynx, pharynx, soft palate (CN IX, X)
lesion of nucleus ambiguus
hoarsness
difficulty swallowing
sx: arch of soft palate is drooped, uvula deviated AWAY from side of lesion
preganglionic parasympathetics for thoracic and abd viscera are carried in
visceral motor column (dorsal motor nucleus of X)
T1-L2
preganglionic parasympathetics to pelvic viscera
S2-S4 of spinal cord
sympathetic outputs arise from thorcacolumbar spinal cord segments and synapse where?
in paravertebral and prevertebral ganglia
parasympathetic outputs arise from craniosacral regions and synapse where?
in ganglia in/near effector organs
nucleus solitarius receives taste and sensation from viscera via
CN VII, IX, X
spinal nucleus of V
receives pain and temp info from face and oral cavity
(also receives input from VII, IX, X - area around ear)
lesions –> ipsilateral deficit pain/temp from face
(loss of nearby SST –> contralateral deficit pain/temp of body)
lateral medullary lesion
STT:
pain/temp loss in body (contralateral)
Ambiguus (IX, X):
hoarseness, uvular deviation (contralateral)
Solitarius (VII, IX, X):
taste/sensation from viscera
Spinal V (V. ~VII, IX, X): pain/temp loss in face (ipsilateral)
VIII/ICP:
ataxia/vertigo (ipsilateral)
Horner’s syndrome: damage to descending sympathetics from hypothalamus to ipsilateral face
ventral lesion in spinal cord will probably affect which tracts?
lesion of corticospinal/corticobulbar tracts
damage to inferior cerebellar peduncle may result in ____ on the side of the lesion
damage to inferior cerebellar peduncle may result in ATAXIA on the side of the lesion
Lateral medullary lesions can result in _______ syndrome
Horner’s syndrome
damage to fibers that originate in the hypothalamus and descend to the spinal cord to control sympathetic NS to ipsilateral face
inferior cerebellar peduncle
located dorsolaterally in the rostral medulla.
receives fibers from spinal cord and inferior olivary peduncle.
the major communication cable between the medulla and the cerebellum.
middle cerebellar peduncle
info from cerebellum –> brainstem –> cortex
____________ sit on top of inferior cerebellar peduncle
cochlear nuclei sit on top of inferior cerebellar peduncle
pontine nuclei sends axons to
middle cerebellar peduncle
CN VI and CN III are controlled by
PPRF which receives info from cortex
paralysis of LOWER face tells you right away that you have a lesion
in contralateral corticobulbar pathway
paralysis of WHOLE side of face indicates which type of lesion
lesion of facial nucleus or nerve (LMN)
