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NEUROANATOMY > (6) Brainstem > Flashcards

(6) Brainstem Flashcards

1
Q

are divisions of the brainstem clearest anteriorly/posteriorly

A

anteriorly

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2
Q

what is the pyramidal decussation

A

dividing line between medulla and spinal cord

corticospinal fibres cross one side to another

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3
Q

what is the pontomedullary junction/sulcus

A

where pons are separated from medulla

cranial nerves emerge at side

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4
Q

midbrain begins at levels of the …

A

cerebral peduncles

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5
Q

what are the cerebral peduncles

A

connect brainstem with white matter of cerebrum

form 2 thick band of fibers

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6
Q

brainstem 3 components (top to bottom)

A

midbrain
pons
medulla

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7
Q

medulla ends where?

A

just above the vagal trigone

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8
Q

what is the vagal trigone?

A

small elevation on the floor of 4th ventricle produced by the underlying dorsal motor nucleus of the vagus

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9
Q

pons beings where?

A

at lower border of the inferior colliculus

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10
Q

upper margin of midbrain is extent of..

A

rostral extent of superior colliculus

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11
Q

rostral vs caudal

A

rostral= upper/above

caudal= lower/below

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12
Q

rostral and caudal midbrain divided by

A

line between superior and inferior colliculi

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13
Q

rostral and caudal pons divided by

A

line where the superior cerebellar peduncle forms the roof of the 4th ventricle (called superior medullary velum)

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14
Q

medulla sections open/closed

A

rostral= open (upper)

caudal= closed (lower)
- no 4th ventricle

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15
Q

rostral and caudal medulla divided by

A

caudal limit of the 4th ventricle called obex

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16
Q

above the obex, each level of brainstem is adjacent to ventricular space (name them)

A

midbrain= anterior and posterior to cerebral aqueduct

pons= anterior and posterior to the 4th ventricle

medulla= anterior to the 4th ventricle

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17
Q

what is the obex

A

caudal limit (lower) of the 4th ventricle

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18
Q

3 general areas identified in cross section at any level above obex

A

1) tectum
2) tegmentum
3) large structures appended to anterior surface of the brainstem

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19
Q

what is the tectum

A

area posterior to the ventricular space (mostly found in midbrain)

  • consist of superior and inferior colliculi
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20
Q

what is the tegmentum

A

area anterior to the ventricular space

  • consist of reticular formation, cranial nerve nuclei and tracts, ascend/descending pathways
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21
Q

large structures appended to anterior surface of the brainstem consist of …

A
  • most of the pons of tegmentum are appendages

- pyramids and other structures are appendages of tegmentum

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22
Q

brainstem is a conduit for… (2)

A

1) ascending tracts to reach thalamus and cerebellum

2) descending tracts to reach spinal cord

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23
Q

cranial nerve nuclei associated with brainstem

A
  • mostly all associated

only one cranial nerve no direct association with brainstem= olfactory (CN1)

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24
Q

brainstem intrinsic features (2)

A
  • reticular formation

- associated projections

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25
Q

what is reticular formation?

A
  • stuff left over

contains neurons, nucleus fibres, don’t for discrete components
- neurons and processes

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26
Q

descending motor tracts, brainstem conduits

A

Corticospinal fibres travel in most ANTERIOR past of the brainstem

cerebral peduncle (basis pedunculi)–> basal pons –> medullary pyramids

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27
Q

at highest level if brainstem, corticospinal fibres are found

A

in basis pedunculi (cerebral peduncles)

located ANTERIOR part of brainstem

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28
Q

at any level of the brainstem, where are corticospinal fibers located?

A

ANTERIOR/ventral part of brainstem

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29
Q

cerebral peduncles also carry what type of fibres? (2)

A

corticobulbar (corticonuclear) fibres

corticopontine fibres

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30
Q

what are corticobulbar fibres?

A

descending, mostly bilateral, motor input to cranial nerve nuclei

  • travel to innervate cranial nerve nuclei in brainstem
  • come from cortex, innervate lower motor neuron targets in brainstem
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31
Q

what are cortipontine fibres?

A
  • descending input to pontine nuclei

- fibres originate from nucleus in cerebral cortex, descend and go to level of pons, innervate pontine nuclei

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32
Q

what are pontine nuclei

A

groups of neurons on the pons that project to the cerebellum

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33
Q

corticopontine pathway important for

A

processing by cerebellum

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34
Q

3 tracts from cerebrum to cerebral peduncles

A

corticospinal fibres
corticobulbar fibres
corticopontine fibres

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35
Q

where are corticopontine tracts located

A

at medial and lateral extreme of cerebral peduncle

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36
Q

ascending sensory tracts, brainstem conduits

A

spinothalamic fibres are found LATERALLY

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37
Q

spinothalamic fibres carries sensation of (3)

A

pain
temperature
crude touch

38
Q

posterior column medial lemniscus pathway carries info for (3)

ascending sensory pathways (brainstem conduits)

A

fine touch
vibration
conscious proprioception

39
Q

the posterior columns terminate where?

A

posterior column nuclei

40
Q

2 posterior column nuclei (lower/upper limb)

A

lower= gracilis (medial)

upper= cuneatus (lateral)

41
Q

projections from posterior column nuclei decussate where?

A

in medulla as internal arcuate fibres to form the medial lemniscus

42
Q

medial lemniscus location in the posterior column medial lemniscus pathway

A

start out as midline (medial) structure posterior to pyramids

move progressively laterally, rotate nearly 180 degrees as they ascend

  • relative to spinothalamic fibres
43
Q

ascending (brainstem conduits) to the cerebellum carry what type of info

A

unconscious proprioception

44
Q

3 ascending (brainstem conduits) pathways to the cerebellum

A

anterior spinocerebellar tract

posterior spinocerebellar tract

cuneocerebellar tract

45
Q

anterior spinocerebellar tract (brainstem conduit)

A

crossed projections, primarly from the leg to superior cerebellar peduncle

46
Q

posterior spinocerebellar tract (brainstem conduit)

A

uncrossed projections from leg, via Clarke’s nucleus, inferior cerebellar peduncle

47
Q

cuneocerebellar tract (brainstem conduit)

A

uncrossed projections form arm, via lateral cuneate nucleus, inferior cerebellar peduncle

48
Q

ascending (brainstem conduits) to the cerebellum are all positioned what way?

A

LATERALLY

49
Q

neurons within reticular formation

A

integrative participating in complex motor patterns, respiratory and cardiovascular activity and regulation of level of consciousness

50
Q

what 5 structures are present at the CAUDAL MEDULLA (near spinomedullary transition)

A
  • pyramidal decussation
  • pyramids (most anterior part of brainstem)
  • spinothalamic tract (lateraly)
  • posterior columns (most posterior)
  • caudal regions of posterior columns
51
Q

central canal in caudal medulla

A

remnants of neural tube formation in development

52
Q

posterior columns in caudal medulla cross and terminate in

A

nucleus gracilis (lower)

  • not much end in cuneatus (upper)
53
Q

what 3 main structures are present at the caudal medulla caudal/lower to the obex

A
  • medial lemniscus
  • internal arcuate fibres
  • nucleus cuneatus and gracilis prominent
54
Q

position of medial lemniscus in caudal medulla caudal to obex

A

2 parallel band medially

55
Q

in the caudal medulla, caudal to the obex what do the the medial lemniscus and internal arcuate fibres do

A
  • they are obvious here

- make spinothalamic and posterior spinocerebellar tracts more obvious

56
Q

is fasciculus gracilis present in caudal medulla, caudal to obex

A

NO

  • fibers end in NG
  • there is FC and NC present here
57
Q

what is alteral to the nucleus cuneatus

A

lateral/external cuneate nucleus

58
Q

axons of the lateral cuneate nucleus form the

A

cuneocerebellar tract that is adjacent to posterior spinocerebellar tract

59
Q

medial longitudinal fasciculus in caudal medulla (Caudal to obex)

A
  • its the caudal extend of MLF
  • fibre bundle runs from caudal medulla to midbrain
  • connects different cranial nerve nuclei to coordinate eye and head movements
60
Q

what is the inferior olivary nucleus, where is it present?

A
  • gray matter, posterior to pyramids

- visible in caudal medulla, caudal to obex

61
Q

what structure is most obvious in the rostral (open) medulla

A

inferior olivary nucleus (IO)

62
Q

inferior olivary nucleus forms

A

swellings visibly called the olives, because it is so large

63
Q

IO projects to … and is associated with …

A

projects to the cerebellum via inferior cerebellar peduncle

  • associated with motor coordination and motor learning
64
Q

what other 8 structures are present at the rostral (open) medulla

A
  • well defined pyramids
  • medial lemniscus
  • medial longitudinal fasciculus
  • spinothalamic tract (most lateral)
  • lateral cuneate nucleus
  • ASCT
  • PSCT
  • CCT
65
Q

caudal pons is at the level of the

A

facial colliculus

66
Q

what is the facial colliculus

A

2 swellings in floor of 4th ventricle

  • under are fibres associated with facial nerves
67
Q

what 5 structures are present at caudal pons

A
  • superior peduncle
  • inferior peduncle
  • middle peduncle
  • medial lemniscus (rotated 90 degrees)
  • corticospinal tract (about same position as medulla)
68
Q

in the caudal pons what is between and posterior to corticospinal tract fibres?

A

pontine nuclei and transverse pontine fibres

69
Q

fibres from pontine nucleus cross midline and give rise too… (in caudal pons)

A

give rise to middle cerebellar peduncle

70
Q

mid pons are at the level of

A

trigeminal nerve

71
Q

what structures are present at level of mid pons

A
  • similar structure to caudal pons
  • anterior spinocerebellar tract lateral to the superior cerebellar peduncle
  • NO posterior spinocerebellar tract
72
Q

why is there no posterior spinocerebellar tract at the level of the mid pons?

A

because it is above the level of inferior cerebral peduncle where fibres enter cerebellum

73
Q

what structures are present at rostral pons, near pons-midbrain junction

A
  • similar structure as caudal pis
  • posterior wall of 4th ventricle now formed by superiorly medullary velum
  • medial lemniscus rotated above 90 degrees
  • pontine nuclei- give rise to transverse pontine fibres
74
Q

locus ceruleus in rostral pons

A

group of pigmented (melanin) cells

  • largest group of CNS neurons that are noadrenergic (uses noradrenaline)
  • the pigment is a byproduct of synthesis of the NT noradrenaline
  • part of the reticular formation, have widespread projections to cerebrum
75
Q

neurons of locus ceruleus

A

inactive during sleep

active when awake

very active during periods of attention and vigilance

76
Q

serotonin containing neurons in rostral pons

A

also contains serotonin-containing neurons in the dorsal raphe nucleus

  • no pigment, occupy discrete region
77
Q

what 5 structures are present at caudal midbrain at level of inferior colliculus?

A
  • cerebral peduncles
  • medial lemniscus (curving posteriorly)
  • MLF
  • spinothalamic tract (pain/temperature)
  • PAG: reticular formation region, descending pain control pathway
78
Q

superior cerebellar peduncles at level of the caudal midbrain

A

here they decussate

  • only output fibres from the cerebellum
79
Q

Periaqueductal gray-raphe nuclei pathway

A
  • PAG neurons receive inputs from spinothalamic tract collaterals
  • PAG neurons project to serotonin containing neurons in nucleus raphe magnus in rostral medulla/caudal pons (in reticular formation of lower pons)
  • the raphe magnus neurons then project to posterior (dorsal) horn of the spinal cord
80
Q

pain and temperature signals can pass directly/indirectly

A

directly to neurons in nucleus proprious

indirectly via neurons in adjacent substantia gelatinosa

81
Q

pain and temperature projecting indirectly (pathway)

A
  • spinothalamic tract collaterals project to enkephalin-containing inhibitory interneurons
  • these can inhibit inhibitory interneurons that normally suppress pain-control pathway
  • PAG projections neurons are disinhibited
  • the serotonergic neurons of the raphe magnus project to the substantia gelatinosa (can reduce pain transmission)
82
Q

how do the serotonergic neurons of the raphne nucleus reduce pain transmission (3 ways)

A

1) presynaptically inhibit nociceptive primary afferets
2) post-synaptically inhibit spinothalmamic neurons
3) excite inhibitory enkephalin-containing interneurons that project to spinothalamic neurons

83
Q

summary: pain temperature signals

A

there is a descending inhibitory pathway that involves serotonergic neurons, dorsal raphe nucleus neurons and through variety of pathways can inhibit flow of pain information through dorsal horn

84
Q

what 5 structures are present at rostral midbrain at level of superior colliculus

A
  • cerebral peduncles
  • rostral margin of superior cerebellar peduncle (etc.)
  • brachium of the inferior colliculus
  • substantia nigra
  • red nucleus
85
Q

what is the brachium of the inferior colliculus (at rostral midbrain)

A

connection from inferior colliculus to the medial geniculate nucleus of the thalamus (auditory pathway)

86
Q

substantia nigra position at level of rostral midbrain

A

it is posterior to the cerebral peduncles, and anterolateral to the medial lemniscus

87
Q

substantia nigra can be divided into … (at rostral midbrain)

A

posterior compact part
anterior reticular part

  • both regions have connections with basal ganglia
88
Q

compact part of the substantia nigra (in rostral midbrain) is source of

A

dopaminergic projections to the basal ganglia

89
Q

dopaminergic neurons in compact part can be seen without stain because

A

a byproduct of dopamine synthesis is melanin (dark pigment)

substantia nigra= black substance

90
Q

supply of dopamine to basal ganglia is critical for…

A

normal function

91
Q

decrease/loss of DA leads to

A

dysfunction of basal ganglia= Parkinson disease

92
Q

red nucleus in rostral midbrain receives..

A

projections from the cerebellum

  • has iron-containing neurons that give it a red-pink appearance
  • iron gets iodized to rust

NEUROANATOMY (7 decks)

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