Brainstem Flashcards
Main functions of the brainstem
1) conduit
- for tracts and connections between periphery and cortex
2) cranial nerves
- 3 to 12
3) reticular formation
- visceral function(respiratory, cardiac)
brainstem
midbrain(mesencephalon)
pons
medulla
- postural control, respiration, origins of descending analgesics, decussations, CN’s(3-12), lots of pathways
reticular formation
reticular activating system
- keeps you alert and awake
- works better in vertical position(standing and sitting)
locus ceruleus
lateral zone of reticular formation
- releases norepinephrine
- descending pain control
- aids in awakefulness, attention, and REM sleep
medial zone of reticular formation
location of vital functions
- respiratory, cardiac, swallowing
- reticulospinal pathways
midline zone of reticular formation
raphe nucleus
- releases serotonin
Dopamine
from substantia nigra in midbrain
- “feel good” neurotransmitter(lack of = depression)
- regulate sleep/wake cycles(attentiveness)
Acetylcholine
from pedunculopontine nucleus to cortex, limbic, cerebellum
- arousal and feelings of reward
Serotonin
from Raphe nucleus to dorsal horn and to cortex
Decussation of medial lemniscus
internal arcuate fibers crossing
inferior olive nucleus
upper part of medulla
- receives input from all over CNS
- helps cerebellum with error detection
CN 12
hypoglossal
- located between the corticospinal tract and inferior olivary nucleus
Inferior cerebellar peduncle
Primary INPUT pathway to the cerebellum(afferents)
Afferent pathways into inferior cerebellar peduncles
1) vestibulocerebellar
2) olivocerebellar
3) dorsal spinocerebellar = unconscious proprioception(LE and lower trunk)
4) ventral spinocerebellar
5) Cuneocerebellar = unconscious proprioception(UE and upper trunk)
6) reticulocerebellar = reticular activating system(rejecting info from cerebellum)
nuclei in the medulla
1) vestibular nuclei(4)
2) nucleus ambiguus
3) spinal nucleus and tract of CN 5
nucleus ambiguus
supplies the soft palate, pharynx, larynx, and upper esophagus
- projections via 9,10,11
spinal nucleus and tract of CN 5
- pain and temp(face)
- crude touch –> C3, maybe ipsilateral
medial medullary syndrome
infarction of medullary branch of vertebral artery
- affects medial lemniscus, corticospinal tract, and CN 12
medial medullary syndrome: corticospinal tract
above decussation
- contralateral hemiplesia
- UMN’s signs and symptoms(hypertonicity, spastic paralysis)
medial medullary syndrome: CN 12
ipsilateral affect of 12
- tongue deviates to side affected
medial medullary syndrome: medial lemniscus
above decussation
- contralateral loss of discriminative touch, conscious proprioception, vibration
blood supply to medulla
from the 3 branches of the vertebral artery
- anterior and posterior spinal arteries
- posterior inferior cerebellar artery
blood supply to pons
basilar artery and 2 branches
- anterior inferior cerebellar
- superior cerebellar
primary blood supply to midbrain
posterior cerebral artery
lateral medullary syndrome
Wallenberg’s
- infarction of the posterior inferior cerebellar artery
Affected:
- spinothalamic, trigeminal nucleus, ventral spinocerebellar tract, CN 9, olivocerebellar tract, nucleus amiguous(9,10,11), inferior cerebellar peduncle
- motor pathways are fine, but smooth motor is disrupted
decorticate
above red nucleus, above medulla
- flexed UE and extended LE rigidity
decerebrate
below red nucleus and midbrain, above nuclei
- extended UE and LE rigidity
Lateral medullary syndrome: spinothalamic tract
above decussation
- contralateral loss of pain and temp
Lateral medullary syndrome: trigeminal nucleus
ipsilateral pain and temp to face
Lateral medullary syndrome: nucleus ambiguous
swallowing problems
- CN 9,10,11
Lateral medullary syndrome: inferior cerebellar peduncle
input pathway of cerebellum disrupted(atoxic movements)
Signs of brainstem dysfunction
the 4 D’s:
- Dysphagia
- Dysarthria
- Diplopia
- Dysmetria
Dysphagia
trouble swallowing(choking especially on liquids) - glossopharyngeal, vagus
Dysarthria
speech problems(CN 7 and 12) - dysfunction of muscles(caused by tumor, CVA)(drunk, medication)
Diplopia
eyes don’t track together
- affect corticobulbar tract or CN 3,4,6
Dysmetria
inability to accurately move an intended distance
- typically affects the cerebellum(disrupts pathways to cerebellum)
- Lateral medullary syndrome
tracts that synapse in the pons
corticopontine tract
some corticobrainstem tracts
pontine nuclei
where the corticopontine tract terminates
transverse fibers of the pons
pontocerebellar fibers bundled
- signals from cortex to cerebellum to inform about plan(through middle cerebellar peduncle)
tegmentum on pons
anterior/inferior part of the pons
- reticular formation
- pontinereticular pathway
- nuclei for CN 5(sensation of the face and muscles of mastication)
- 6 (lateral movement of the eye)
- 7 ( facial and chewing muscles)
substantia nigra in midbrain
between tegmentum and crus cerebri
- produces dopamine and stores it
- Parkinson’s = degeneration of substantia nigra, therefore decrease in dopamine
tegmentum of midbrain
contains:
1) red nucleus
2) CN nuclei 3 & 4
3) medial lemniscus
4) medial longitudinal fasciculus
tectum of midbrain
superior colliculus
- tectospinal tract(visual-grasp reflex)
red nucleus
origin of rubrospinal tract
- helps update motorplans with cerebellum and motor planning
- flexor of UE, but not hand
CN 3 nuclei
occulomotor
- movement of the eye except lateral and inferior-medial
- pupil constriction, levator palpibrae
- can be compressed into tentorium by increased cranial pressure(presents with fixed dilated pupils)
peripheral visual information
temporal field
- crosses at optic chiasm (contralateral)
- processed on opposite temporal lobe
nasal visual information
stays ipsilateral
pathways of visual information
Unconscious = optic nerve–>optic chiasm–> optic tract–>superior colliculus(relay area)
Conscious = optic nerve–>optic chiasm–>optic tract–>lateral geniculate nucleus–>primary visual cortex
right homonymous hemianopsia
lesion at the L optic tract
- lose right part of visual field for both eyes
superior cerebellar peduncle
primary OUTPUT pathway of cerebellum
- detects errors in motor plan and updates motor cortex
- R side of cerebellum updates L side of cortex
- L side of cerebellum updates R side of cortex
- cerebellum controls ipsilateral part of body
- everything out of the cerebellum leaves through the superior cerebellar peduncle
parietal lobe
processes spatial information(where it is)
- dorsal stream
temporal lobe
what it is you are seeing(ventral stream)
lesion affecting corticospinal tract
motor impairment(contralateral)
- hemiparesis
- hemiplesia
lesion affecting corticopontine tract
some cerebellar signs
lesion affecting the corticobulbar tract
lack of motor in lower face(contralateral)
- tongue weakness contralateral
lesion at CN 3
no pupil retractions
- eye almost closed
reticular formation
1) integrates sensory and cortical information
2) regulates somatic motor activity, autonomic function, and consciousness
3) modulates nociceptive/pain information
major reticular nuclei
1) ventral tegmental area
2) pedunculopontine nucleus
3) raphe nuclei
4) locus coeruleus and medial reticular area
ventral tegmental area
produces dopamine
- part of the reticular formation
- substantia nigra also produces dopamine
pedunculopontine nucleus
produces ACh
- located in the caudal midbrain
- influences movement
raphe nuclei
produces serotonin
- located along the midline of the brainstem
locus cereleus and medial reticular zone
produces norepinephrine
- in reticular formation
what function will be disrupted by a lesion in the anterior medulla?
tongue control
- lesion would effect CN 12
