Brainstem Flashcards
what are the structures in the brainstem?
CN nuclei and pathways
vertical tracts
connections w/cerebellum
major centers and nuclei
what are the vertical tracts in the brainstem?
sensory (ascending) tracts:
- DCML
- spinothalamic
- spinocerebellar
- trigeminal lemniscus
motor (descending) tracts:
- vestibulospinal
- corticospinal
- rubrospinal
- reticulospinal
autonomic (descending) tracts:
- lateral and medial corticospinal
- vestibulospinal
- rubrospinal
- reticulospinal
what does the DCML do?
light touch, conscious proprioception
what does the spinothalamic tract do?
crude touch, temp, fast nociception
what is the connection w/ the cerebellum?
peduncles
what are the major centers and nuclei?
autonomic function
reticular function
what are the longitudinal sections of the brainstem?
most ventral-basilar part (basis pedunculi)
middle-tegmentum
most dorsal-tectum
basis pedunculi
most ventral longitudinal section of the brainstem
lots of motor structures including motor nuclei and axons from cortex
tegmentum
middle longitudinal section of the brainstem
contains a lot of sensory nuclei and some ascending tracts
reticular formation, sensory nucleus, and medial longitudinal fasciculus (MLF)
tectum
most dorsal longitudinal section of the brainstem
midbrain only
involved in control of eye and head movement
rule of 4 in the brainstem
4 structures in the midline begin with M
4 structures in the side begin with S
4 CNs in medulla, 4 in pons, 4 above pons (2 in midbrain)
4 motor nuclei in midline that divide equally into 12 (except 1 and 2)
- CN 3, 4, 6, 12
- CN 5, 6, 7, 9, 10, 11 in lateral brainstem
rule of 4: medial and lateral organization of the BS
4 Ms:
- motor tracts
- MLF
- medial lemniscus
- motor nuclei
–> CN 3, 4 in midbrain
–> CN 6 in pons
–> CN 12 in medulla
4 Ss:
- sympathetic tract (hypothalamospinal and hypothalmobulbar tracts)
- spinothalamic tract
- spinocerebellar tract
- sensory nuclei
–> CNS: midbrain, pons, medulla (Trigeminal tract)
–> CN 7 in pons
–> CN 8 in pons and medulla
–> CN 9, 10 in medulla
rule of 4: CNs
1-4 above pons
5-8 in pons
rest in medulla w/exception of 8 and 11
- 8 starts in pons, ends in medulla
- 11 in SC
connection w/cerebellum
cerebellar function dependent on connection w/BS
what are the 4 parts of the midbrain?
basis pedunculi
tegmentum
tectum
medial longitudinal fasciculus
basis pedunculi
anterior structure of the midbrain
cerebral peduncles
SN
also part of basal ganglia
tegmentum
largest portion of midbrain
sensory tracts
-retiular formation: midbrain to medulla
- autonomic pathways (hypothalamospinal tract (sympathetic))
- MLF (coordination of eye and head movements)
- CN 5-8 nuclei
oculomotor complex
CN 4 nuclei - trochlear
PPN
red nucleus
PAG
trigeminal lemniscus
what is in the oculomotor complex?
CN 3 nuclei
Edinger-Westphal nuclei (parasympathetic s of CN 3)
- innervates ciliary muscles of eye that adjust thickness of lens and constrict pupil
what is the role of CN 4 (trochlear)
eye adduction
superior oblique muscle
what does the PPN do?
modulates reticulospinal activation
what does the red nucleus do?
controls upper extremity flexors
descending tract (rubrospinal)
what is the role of the PAG?
pain modulation
one of the key areas of the brain that can spread ascending pain signal
what is the role of the trigeminal lemniscus?
info from face about light touch and conscious proprioception
midbrain tectum
pretectal areas - part of visual system
superior an inferior colliculus - head and eye movements
what is the role of pretectal areas
visual system
eye reflexes
located right in front of sup/info colliculus
what is the role of the superior and inferior colliculus?
superior: reflexive eye and head movements in response to tactile info
inferior: auditory info contributing to visual attention
MLF
located near midline bilaterally
ascending and descending fibers
coordinate eye movement
- connects CN 3, 4, 6
- integrates eye movement w/head movement (CN 8)
what does damage to the MLF result in?
gaze palsy-can’t move eyeballs
pons
major motor processing center
higher level respiratory control
most descending tracts pass through anterior pons (basilar part)
tegmentum (post, bordering 4th ventricle)
most descending tracts pass through the basilar part of the pons. what are the 2 exceptions to this?
corticopontine tract: cortex to pons
corticobulbar tract: cortex to CN nuclei innervating face, head, and neck muscles
- facial expressions, muscles of mastication, pharynx, larynx, and tongue
medulla
vasoconstricts/dilated, coughing, swallowing
needed for survival functions
ventrally located
pyramids: rubrospinal and lateral corticospinal go through pons here
olive: lateral to pyramids
posteriorly is inferior peduncle connecting medulla and 4th ventricle
pontomedullary junction
connection b/w pons and medulla
cochlear and vestibular nuclei
medial and lateral vestibulospinal tracts
pontomedullary reticular formation
what do the cochlear and vestibular nuclei do?
auditory and vestibular inputs to CN 8
output to medial and lateral vestibulospinal tracts
what do the medial and lateral vestibulospinal tracts do?
postural muscles activity
head and eye movements-MLF
what does the pontomedullary reticular formation do?
coughing, hiccuping, sneezing, yawning, shivering, gagging, vomitting, swallowing, laughing, crying
what does the superior olive contribute to?
locating sounds
what is in the rostral medulla?
nucleus ambiguus
hypoglossal nucleus (CN 12)
solitary nucleus
inferior olivary nucleus
what is the nucleus ambiguus and what does it do?
motor efferent
controls muscles in pharynx and larynx via CN 9 and 10
shared motor nuclei for CN 9 and 10
damage=difficulty swallowing, dysphonia, and instability of HR
CN 9-soft pallette and pharynx
CN 10-vagus-slows HR (cardiac parasympathetic activity)
what is the solitary nucleus and what does it do?
visceral sensory nucleus
visceral and taste efferents (CN 7)
cardiorespiratory centers (inputs from baroreceptors in carotid body and aortic arch -CN 9 and 10)
lesion=loss of taste and instability of BP
what is the inferior olivary nucleus and what does it do?
irregularly shaped nucleus
perception of time and control of movement (olivocerebellar tracts)
afferent from motor and sensory corticies
efferent connection going out of cerebellum
timing of movement
what is in the caudal medulla?
pyramids (corticospinal tract axons)
- lateral corticospinal is most important voluntary movement tract
spinothalamic tracts
DCML
CN 5
MLF
what are the pathways to the medulla?
cerebrovestibular tract
what are the pathways from the medulla?
spinocerebellar tract
olivocerebellar tract
vestibulocerebellar tract
reticulocerebellar tract
what is in the reticular formation?
4 reticular nuclei
-VTA
- PPN
- raphe nuclei
- locus coeruleus and medial reticular zone (MRZ)
ascending/descending projections
- reticulospinal tracts (2)
- raphespinal tract
- ceruleospinal tract
what are the functions of the reticular formation?
integrates sensory and cortical info
regulates motor activity, autonomic function, and consciousness
modulates nociceptive info-always ascending info
what is the ventral tegmental area (VTA), where is it located, and what does it do?
midbrain
dopamine released (SN in midbrain also released dopamine)
motivation, decision-making, pleasure/reward
where is most dopamine released into the CNS from?
midbrain (SN and VTA)
what is the PPN, where is it located, and what does it do?
caudal midbrain
releases ACh (excitatory/inhibitory), GABA (inhibitory), and glutamate (excitatory)
motor control
- GP, STN influence reticulospinal tract neurons
- reticulospinal tract-posture and gross limb movement
- limbic system
lesion=issues w/initiation of movement
what is the raphe nuclei, where is it located, and what does it do?
midbrain, pons, and medulla
releases serotonin
pontine raphe nuclei project mainly to cerebrum and modulate activity throughout cerebral cortex
- arousal and mood
medulary raphe nuclei are involved in pain modulation and provides serotonin to dorsal horn of SC inhibiting nociceptive info
- sensory and autonomic activity
- decreases pain-one of the fastest routes to decrease pain
what is the locus coeruleus (LC) and medial reticular zone (MRZ), where are they located, what do they release, and what do they do?
pons
LC and MRZ: NE
MRZ: E
arousal, attention, autonomic regulation
LC: direct attention to food and enemies; inhibits spinothalamic neuron to modulate pain signals
nonspecific excitation of motor and interneurons in SC
MRZ: psychological responses to stress and panic- (related to sympathetic response)
what are the 4 descending tracts of the reticular formation?
medial reticulospinal tract
lateral reticulospinal tract
raphespinal tract
ceruleospinal tract
what does the medial reticulospinal tract do?
postural control
pons
what does the lateral reticulospinal tract do?
gross limb movement
medulla
what does the raphespinal tract do?
pain modulation (dorsal horn)
cardiac influence (lateral horn)
nonspecific activation of interneurons and motor neurons in SC (ventral horn)
does the ceruleospinal tract do?
enhances activity of motor neuron pool and interneuron pool throughout SC
do same as ventral raphespinal w/different mechanism
what structures are involved in the regulation of consciousness?
reticular formation
ascending reticular activating system (ARAS)
cerebral consciousness system
what is the ARAS?
formation and cerebral consciousness system
actively induces sleep
what are the structures of the cerebral consciousness system?
basal forebrain
thalamus
cerebral cortex
what would a lesion in the structures that regulate consciousness result in?
difficulty controlling consciousness and wakefulness
what is the blood supply of the midbrain?
posterior cerebral artery (branch of basilar artery)
what is the blood supply of the pons?
anterior inferior cerebellar artery (AICA)
superior cerebellar artery
what is the blood supply of the medulla?
basilar artery (paramedian and circumferential branches)
posterior inferior cerebellar artery (PICA)
anterior spinal artery
posterior spinal artery
