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Neuro > CH 10: Organization of the brainstem and CNs > Flashcards

CH 10: Organization of the brainstem and CNs Flashcards

1
Q

what is the medulla?

A

the most caudal part of the brainstem

extends rostrally for 2.5 cm to the caudal border of the pons

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2
Q

the central canal of the SC continues through the ____ and flares open into the ____?

A

through the caudal half of the medulla

at a point called the obey, flares open into the wide cavity of the 4th ventricle

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3
Q

the rostral part of the medulla occupies the?

A

floor of the 4th ventricle

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4
Q

the roof of the 4th ventricle consists of the ?

A

tela choroidea

the choroid plexus

cerebellum

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5
Q

what is the tela choroidea?

A

a thin sheet of apposed ependyma and pia mater

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6
Q

what is the choroid plexus

A

tela choroidea with good vessels between the ependyma and pia

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7
Q

what can be seen from the anterior aspect of the medulla?

A

the pyramids

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8
Q

what are they pyramids?

A

formed by the pyramidal (corticospinal and corticobulbar) tracts

forms 2 longitudinal ridges on either side of the ventral median fissure

the decussation of the pyramids can be seen as bundles of fibers crossing and obliterating the fissure at the extreme caudal end of the medulla

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9
Q

what can be seen from the lateral aspect of the medulla?

A

the ventrolateral sulcus

dorsolateral sulcus

olive

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10
Q

what is the ventrolateral sulcus?

what exits from this groove?

A

extends along the lateral border of the pyramid

the rootlets of the hypoglossal nerve (12) exit

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11
Q

what exits from the dorsolateral sulcus?

A

cranial portion of the accessory nerve (9)

vagus nerve (10)

glossopharyngeal nerve (11)

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12
Q

how does the accessory nerve exit?

A

the cranial portion exits through the dorsolateral sulcus

the spinal portion originates in the gray matter of C2-5. its rootlets exit through the lateral funiculus of the cord, join, and then ascend along the lateral surface of the medulla

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13
Q

what is the olive?

A

the prominent oval swelling of the lateral area of the medulla between the ventrolateral and dorsolateral sulci

marks the site of the inferior olivary nuclear complex inside the medulla

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14
Q

what can be seen from the posterior aspect of the medulla?

A

fasciculus gracilis

fasciculus cuneatus

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15
Q

what marks the termination of the FC and FG?

A

FC= cuneate tubercle

FG= clava

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16
Q

the axons of neurons in the nucleus gracilis and nucleus cuneatus extend ventrally into the?

A

tegmentum (floor) of the medulla

thus, at the rostral end of these nuclei, the dorsal area “opens up” exposing the floor of the fourth ventricle rostral to the obex

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17
Q

what are the 2 pairs of swellings seen in the floor of the 4th ventricle?

A

vagal trigone

hypoglossal trigone

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18
Q

what is the vagal trigone?

A

lateral ridge in the floor of the 4th ventricle

bulge indicates the location of the dorsal motor nucleus of the vagus

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19
Q

what is the hypoglossal trigone?

A

medial ridge of the floor of the 4th ventricle

bulge indicates the location of the hypoglossal nucleus

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20
Q

what is the striae medullares of the 4th ventricle?

what do these fibers mark laterally?

A

ridges formed by fibers passing toward the cerebellum

laterally, these fibers mark the location of the lateral recesses

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21
Q

what is the lateral recess?

A

where opening in the 4th ventricle (foramina of Luschka) allow CSF to flow from the 4th ventricle into the subarachnoid space

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22
Q

how does CSF leave the 4th ventricle?

A

lateral recesses

foramen of Magendie- a single, midline opening at the Obex

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23
Q

what is the pons?

A

a large tissue mass rostral to the medulla

on the ventral surface of the brainstem, the cerebral peduncles pass into the pons from above, and the pyramids emerge from below

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24
Q

what can be seen on the anterior aspect of the pons?

A

a band of thick transverse fibers- constitute the pons proper or the “bridge”- occupies the entire anterior aspect

the basal sulcus-

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25
Q

what is the basal sulcus?

what coincides with it ?

A

shallow furrow extends along the midline and coincides with the course of the basilar artery

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26
Q

what CN exits from the inferior pontine sulcus?

A

the abducens nerve (6) at the caudal border of the pons close to the pyramids

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27
Q

what can be seen from the lateral aspect of the pons?

A

middle cerebellar peducles (brachia pontis)

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28
Q

what is the middle cerebellar peduncle?

A

transverse fibers of the pons converge to form compact lateral bundles that attach the pons to the overlying cerebellum

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29
Q

what does the cerebellopontine angle consist of?

A

the triangular space formed between the caudal border of the middle cerebellar peduncle, the adjoining part of the cerebellum and the upper part of the medulla

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30
Q

what CNs emerges from the cerebellopontine angle?

A

facial (7)

vestibulocochlear (8)

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31
Q

where does the trigeminal nerve (5) emerge?

A

penetrates the brachium pontis near the middle of the lateral surface of the pons

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32
Q

what can be seen on the posterior aspect of the pons?

A

forms the rostral part of the floor of the 4th ventricle
at its widest point, this triangular area contains the pontomedullary junction and the lateral recesses of the ventricle.

the facial colliculus superior cerebellar peduncles

anterior medullary velum

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33
Q

what is the facial colliculus and what forms it?

A

lies rostral to the lateral recess in the floor of the 4th ventricle.

the abducens nucleus and the fibers of the facial nerve that cross over the nucleus of abducens form this colliculus (little hill)

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34
Q

what do the superior cerebellar peduncles form?

what joins it to form the roof of the ventricle?

A

forms the walls of the 4th ventricle at this level

the cerebellar vermis in the caudal pons and the anterior medullary velum rostrally join these peduncles in the midline and complete the roof

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35
Q

what does the midbrain consist of?

A

a short segment of brain stem between the pons and the diencephalon

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36
Q

what is the cerebral aqueduct?

A

a markedly narrow tubular passage connecting the 3rd and 4th ventricles

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37
Q

what can be seen from the anterior aspect of the midbrain?

A

2 rope like bundles of fibers- cerebral peduncles or crura cerebra and a deep interpeduncular fossa that separates them, form the inferior surface

the optic tract skirts around each cerebral peduncle just before it disappears into the cerebral hemisphere above.

at its caudal end, the peduncle passes directly into the basilar portion of the pons

38
Q

what CN exits from the sides of the interpeduncular fossa?

A

the oculomotor nerves

and emerge on the surface at the transverse groove between the pons and the midbrain

39
Q

what can be seen from the posterior aspect of the midbrain?

A

corpora quadrigemina

40
Q

the posterior surface of the midbrain=

A

tectum

41
Q

what is the corpora quadrigemina?

A

4 rounded elevations

superior colliculi
inferior colliculi

42
Q

what nerve emerges from the tectum?

A

the trochlear nerve (4)
smallest CN
emerges from tectum just behind the inferior colliculi after decussating in the anterior medullary velum

43
Q

what arteries provide the primary source of blood to the brain stem?

A

vertebral arteries

44
Q

direct branches of the L and R vertebral arteries supply the ..

A

anterolateral parts of the medulla

45
Q

the anteromedial medulla receives blood from the

A

anterior spinal artery

46
Q

at the pontomedullary junction, the 2 vertebral arteries..

A

join to form the basilar artery

47
Q

the basilar artery supplies..

A

branches to the pons and the midbrain

48
Q

branches of both the vertebral and basilar arteries wrap ..

what do these arteries include?

A

dorsally around the brain stem to supply the dorsal aspect of the brain stem and the entire cerebellum

posterior inferior cerebellar arteries
anterior inferior cerebellar arteries
superior cerebellar arteries

49
Q

the posterior inferior cerebellar arteries supply the

A

medulla as well as the cerebellum

50
Q

the anterior inferior cerebellar arteries provide blood for the

A

pons and the cerebellum

51
Q

the superior cerebellar arteries distribute to ?

A

both the midbrain and the cerebellum

52
Q

at the rostral end of the midbrain, the basilar artery terminates by …?

A

dividing into the R and L posterior cerebral arteries

53
Q

where does the R and L posterior cerebral arteries provide blood for?

A

passes superior to the tentorium cerebelli to supply the posterior and ventral surfaces of the cerebral hemispheres

54
Q

what is the posterior portion of the pons?

A

tegmentum

55
Q

what is the anterior portion of the pons?

A

basilar portion

56
Q

what is the roof portion of the pons?

A

tectum

overlying the cavity of the ventricle
becomes expanded and specialized to form the cerebellum

57
Q

where do the corticospinal tracts appear in the pons ?

A

in a central location in the basilar portion

58
Q

the gray matter that surrounds the corticospinal tracts in the pons contains cells of the ?

A

pontine nuclei

transverse pontine fibers (pontocerebellar tract) crossing from one side to the other, posterior and anterior to the corticospinal tracts, consist of axons from cell bodies in the pontine nuclei

59
Q

the fibers from the pontine nuclei of one side form the ___ and terminate in the ____?

A

contralateral middle cerebellar peduncle and terminate in the cerebral cortex

60
Q

the pontine nuclei receive input from the ___?

what do their projections to the cerebellum constitute?

A

ipsilateral cerebrum

their projections to the cerebellum constitute a major route by which the cerebral cortex communicates with the cerebellar cortex (travels through the cerebral peduncle of the pons)

61
Q

how is the medial lemniscus oriented in the medulla ?

A

in the anterior-posterior axis (CTLS)

62
Q

how is the medial lemniscus oriented in the lower pons?

A

in the tegmentum of the pons the ML has shifted and the long axis of the ellipse extends transversely along the boundary with the basilar portion of the pons

63
Q

what is the position of the MLF in the lower pons? what does it primarily consist of at this level?

A

retains its position near midline in the floor of the fourth ventricle

MLF primarily consists of ascending fibers- these fibers arise in the vestibular nuclei and project to the nuclei supplying the extra ocular muscles

the descending interstitiospinal and pontine reticulospinal tracts become partially intermingled with the MLF at this level

64
Q

what is the trapezoid body?

A

an auditory relay structure- appears as a prominent band of decussating fibers in the anterior part of the tegmentum

its fibers interlace at right angles with the rostrocaudally oriented fibers of the ML

65
Q

what is the central segmental tract/bundle?

A

an isolated bundle in the anterior part of the RF that contains descending pathways (mainly rubroolivary tracts) and part of the important ascending RF projections to the thalamus and hypothalamus

also carries ascending taste fibers from the solitary nucleus to the ventral-postero-medial nucleus of the thalamus

66
Q

what is the position of the spinal nucleus of V at the level of the lower pons?

A

spinal nucleus and tract of V have NOT changed their position but fibers of the middle cerebellar peduncle cover the lateral side

67
Q

what CNs appear in the lower pons?

what are their functional components?

A

CN 5:
spinal nucleus of V – GSA

CN 6- abducens nucleus– GSE

CN 7- motor nucleus of 7– SVE

CN 8- vestibular nucleus– SSA

68
Q

before leaving the BS, the fibers of the facial nerve form an internal loop “___”

what is the course of the loop?

where does it exit?

A

“internal genu of the facial nerve”

courses posteromedially toward the floor of the 4th ventricle and passes close and just caudal and medial to the nucleus of the abducens nerve

then courses rostrally and laterally around the abducens nucleus and takes a direct course anterolaterally and slightly caudally to its exit at the pontomedullary junction

69
Q

what do the fibers of the motor nucleus of the facial nerve innervate?

A

branchiomeric muscles underneath the skin of the face– controls facial expression SVE

70
Q

what is the course of the abducens nerve?

where does it exit?

A

fibers take a straight course through the tegmentum of the pons and exit close to the lateral border of the pyramidal tract on the anterior aspect of the BS

71
Q

what does the abducens nerve innervate?

A

the lateral rectus muscle in the orbit

GSE

72
Q

where does the vestibular nucleus lay in the lower pons?

what does it include?

A

vestibular nuclei continue to occupy a lateral area in the floor of the 4th ventricle

the individual sub nuclei at this level include the lateral, superior and medial sub nuclei

the spinal (inferior) nucleus remains confined to the medulla

73
Q

the basilar portion of the pons in the middle pons is..

A

wider and thicker

74
Q

what are the 2 oval shaped nuclei that lie side by side in the posterolateral part of the tegmentum?

A

laterally- the main (principal) sensory nucleus of the trigeminal (GSA- discriminative sensation to the face)

medially- the motor nucleus of the trigeminal nerve (SVE- muscles of mastication)

75
Q

cells from the mesencephalic nucleus of V carry ___?

A

signals from stretch receptors in the muscles of mastication

most make monosynaptic connections with the motor nucleus of CN V and contribute the afferent signals for the jaw reflex

76
Q

small filaments of this nerve pass posteriorly and rostrally to the?

A

pass to the mescencephalic tract of V

77
Q

trigeminal nerve fibers emerge from the pons by:

A

passing directly through the middle cerebellar peduncle

78
Q

the superior cerebellar peduncles appear :

A

in the walls of the fourth ventricle of the middle pons as large compact bands

79
Q

what is the anterior medullary velum?

A

forms the roof of the ventricle

80
Q

what does the upper pons consist of?

A 
basilar portion
MLF
RF
LSTT
VTTT
ML
mesencephalic nucleus of V
81
Q

the corticospinal and corticobulbar tracts occupy the ____ in the midbrain?

A

cerebral peduncle

82
Q

what is the substantial nigra?

where is it?

A

lies between the cerebral peduncle and the tegmentum

produces dopamine

83
Q

where is the ML in the caudal midbrain?

A

displaced laterally and slightly rotated

lies closely to the LSTT

84
Q

the lateral lemniscus contains:

A

ascending auditory fibers – fibers terminate dorsally into the nucleus of the inferior colliculus

85
Q

what CN is located in the caudal half of the midbrain?

where is it located?

A

CN 4- trochlear- GSE

lies near the MLF in there anterior part of the central periaqueductal gray matter

86
Q

in the rostral midbrain, the cerebral peduncle and the substantial nigra …

A

continue to occupy the basal portion of the midbrain

87
Q

the crossed fibers of the superior cerebellar peduncle pass into the ?

A

red nucleus; others pass forward to the thalamus

88
Q

what does the red nucleus do?

A

rubrospinal tract

distal movement

89
Q

What CN nucleus lies in the rostral midbrain?

A

CN III- oculomotor:
GSE
GVE- Edinger-wesphal nucleus

the nuclear complex of the oculomotor nerve lies in the anterior part of the central gray matter with the MLF beside it

90
Q

the root fibers of the oculomotor nerve stream..?

what does CN 3 do?

A

ventrally through and around the red nucleus before converging at their exit in the interpeduncular fossa

from there, the root fibers travel to the orbit where they inner vat 4 of the 6 muscles that control eye movements and one muscle that elevates the eyelid (GSE)

the nerve also contains preganglionic parasympathetic fibers which constrict the pupil and change the shape of the lens within the eye (Edinger-wesphal- GVE)

91
Q

in transverse sections through the rostral midbrain, where the midbrain joins the diencephalon, the _____ appear to be protrusions on the lateral surfaces of the midbrain

A

medial geniculate bodies/nuclei (vision)

not a BS structure, but the most ventral, caudal nuclei of the thalamus

Neuro (48 decks)

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