Brain Stem Tracts and Anatomy Flashcards
1
Q
parts of the brain stem
A
in continuous order: midbrain, pons, medulla (oblongata)
2
Q
pair of fiber bundles ventral to the midbrain in the brain stem
A
cerebral peduncles (feet) major tract of axons of voluntary motor neurons (corticospinal tract)
3
Q
the large bulge ventral to the pons in the brain stem contains a massive series of neurons that project to overlying…
A
cerebellum
4
Q
what do the medullary pyramids contain
A
corticospinal tracts (which are the same tracts that run through cerebral peduncles)
5
Q
bulging out from the upper lateral portion of the medulla is a pair of ___, which contain neurons that project almost exclusively to the cerebellum
A
olives
inform cerebellum in errors in smooth execution of movement
6
Q
where are the superior and inferior colliculus and what do they do
A
dorsal side of midbrain (two pairs of small mounds)
superior- vision (gaze)
inferior- auditory stimuli
7
Q
where is the fourth ventricle
A
on top of the entire pons and part of the medulla
8
Q
which cranial nerve is not a true cranial nerve (name and number)
A
cranial nerve XI (11), spinal accessory (motor)
exits through foramen magnum. arises from cervical spinal cord
9
Q
which 3 cranial nerves do not arise from brain stem
A
I (olfactory), II (optic), XI (spinal accessory- motor)
10
Q
the __ is home to cranial nerves III and IV
the __ is home to cranial nerves V, VI, VII, VIII
A
midbrain- III (oculomotor) and IV (trochlear)
pons- V (trigeminal), VI (abducens), VII (facial), VIII (vestibulocochlear)
11
Q
the largest cranial nerve, and the only true pontine nerve (because it enters/exits directly from substance) is ___
A
cranial nerve V (trigeminal, mixed)
cranial nerves VI, VII, VIII are at pons-medulla junction
12
Q
the only completely crossed cranial nerve is __
A
IV, trochlear (motor, eye movement)
13
Q
name/number of the three sensory cranial nerves
A
I (olfactory), II (optic), VIII (vestibulocochlear- somewhat mixed though)
14
Q
name/number of motor cranial nerves
A
III (oculomotor)- eye IV (trochlear)- eye VI (abducens)- eye XII (hypoglossal) XI (accessory)- cervical spinal cord
15
Q
name/number of four mixed cranial nerves
A
V (trigeminal)
VII (facial)
IX (glossopharyngeal)
X (vagus)
16
Q
cranial nerve I
A
olfactory, sensory
17
Q
cranial nerve II
A
optic, sensory
18
Q
cranial nerve VIII
A
vestibulocochlear, sensory (somewhat mixed)
19
Q
cranial nerve III
A
oculomotor (motor)
20
Q
cranial nerve IV
A
trochlear (motor)
21
Q
cranial nerve VI
A
abducens (motor)
22
Q
cranial nerve XII
A
hypoglossal (motor)
23
Q
cranial nerve XI
A
accessory (motor)- cervical spinal cord
24
Q
cranial nerve V
A
trigeminal (mixed)
25
cranial nerve VII
facial (mixed)
26
cranial nerve IX
glossopharyngeal (mixed)
27
cranial nerve X
vagus (mixed)
28
the axons of the corticospinal tract run down entire length of brain stem and cross at lower medulla levels at the ___?
pyramidal decussation
29
this tract runs down the entire length of the spinal cord and provides a way for the diencephalon (specifically the hypothalamus) to control sympathetic tone at spinal cord level
hypothalamic axons/fibers (hypothalamospinal fibers)
30
spinothalamic tract
ascending axons carrying sensation from limbs/trunk of pain/temp/itch
runs parallel (but it opposite direction) to descending hypothalamic axons
31
dorsal columns of brain stem
sensory axons that process touch, vibration, pressure, proprioception from tactile/ muscle position receptors at limbs and trunk
synapse on second neurons in lower medulla in dorsal column nuclei
32
the dorsal columns (sensory axons of limbs/trunk) synapse on dorsal column nuclei in lower medulla, which cross and form ___
medial lemniscus
33
every brain stem cross section will feature these 4 tracts:
corticospinal tract
descending hypothalamic fibers
spinothalamic tract
medial lemniscus
34
this tract descends medially and ventrally through the entire brain stem. what is?
corticospinal tract. always medial and ventral (front) through the midbrain to pons to medulla (goes top to bottom- descending)
35
medial brain stem strokes have potential to lesion what tract?
corticospinal tract (ventral and medial running)
36
after descending through the medial and ventral portion of the brain stem, the axons of the corticospinal tract cross at the lower medulla at the pyramidal decussation, and from there descend the spinal cord in the ____ portion of the ___ matter
corticospinal tract- lateral portion of spinal cord white matter
37
the corticospinal tract axons cross at pyramidal decussation, run through lateral portion of white matter in spinal cord, then synapse on lower motor neurons whose bodies are in the ___ of the spinal cord ___ matter
UMN- axons in lateral white matter of spinal cord
| LMN- bodies in ventral horns of gray matter of spinal cord
38
spastic weakness or paresis develops from what kind of lesion? patient will also present with hyperactive muscle stretch reflexes
lesion in corticospinal tract (UMN). Paresis will be contralateral and below point of lesion
39
why does lesion of UMN in corticospinal tract result in hyperactive muscle stretch reflexes?
UMN have net inhibitory effect on muscle stretch reflexes, so loss of innervation disinhibits muscle stretch reflexes
40
Babinski sign, and what does it signify?
backwards cutaneous reflex (upgoing toes), signifies corticospinal tract lesion
41
hypothalamic axons descend through ___ portion of brain stem
lateral
42
a lateral brain stem vascular syndrome has the potential to affect what tract?
descending hypothalamic fibers which run through lateral portion of brain stem
43
ipsilateral central Horner's syndrome is caused by disruption of what?
descending hypothalamic axons (hypothalamospinal fibers)
| disruption in hypothalamus control over sympathetic innervation to face, scalp, smooth muscles in orbit
44
what are the three neurons of sympathetic pathway
1. hypothalamus (above brain stem)- descends through entire brain stem, lateral portion
2. upper thoracic spinal cord (T1-T3)- descend through sympathetic trunk
3. superior cervical ganglion- provides all sympathetic innervation
45
patient presents with ipsilateral miosis (constricted pupil), ptosis (eyelid drooping), anhydrosis (loss of sweating), and orthostatic HTN (drop in bp from lying to standing). what is likely?
ipsilateral central Horner's syndrome (loss of SNS input from hypothalamus)
46
orthostatic htn
bp drop from lying to standing
47
this tract arises at spinal cord levels, ascends up entire length of brain stem, and terminates in the thalamus in the diencephalon above the brain stem. what is?
spinothalamic tract
ascends laterally to descending hypothalamic fibers
48
these two axon tracts are located in the lateral portion of the brain stemp
spinothalamic(ascending) and hypothalamic (descending)
49
where are the three synapsing neurons of the spinothalamic tract found?
1. spinal cord- dorsal root
2. ipsilateral dorsal horn (cross midline of spinal cord)
3. ventral posterolateral thalamus- these project up to primary somatosensory cortex
50
your right hand is itchy. which side of your brain receives the signal
left side- itch sensation relayed by spinothalamic tract is contralateral (second neuron crosses midline of spinal cord)
51
describe how the orientation of the medial lemniscus changes as it ascends
medial lemniscus is medial in brain stem, then progressively becomes lateral as it ascends up, until it is totally shifted to lateral vascular territory when it gets to midbrain
also shifts from vertical organization to flattening out (turns medial to lateral as it rotates)
52
this tract relays modalities of touch, pressure, vibration, and proprioception, to the contralateral cortex. what is?
medial lemniscus
3-neuron sensory processing pathway. medial lemniscus axons represent crossed axons of second neuron
53
what are 3 neurons of medial lemniscus tract?
1a. modality sensitive dorsal roots, T6 and below --> 2a. these synapse up to fasciculus gracilis (more medial)
1b. modality sensitive dorsal roots, T5 and above--> 2b. these synapse up to fasciculus cuneatus (more lateral)
2. medial lemniscus- cross in lower medulla
3. ventral posterolateral thalamus (these project to somatosensory cortex)
54
where do modality sensitive dorsal roots below T6 synapse in medial lemniscus tract? what about those above T5?
T6 and below- project up to medial fasciculus gracilis
| T5 and above- project up to lateral fasciculus cuneatus
55
effect of medial lemniscus lesion
always results in loss of touch, pressure, vibration sense that is contralateral and below the lesion (axons of medial lemniscus cross the midline at lower medulla)
56
patient touches a hot pan with their left hand but doesn't feel anything. where and on what side of their brain stem do they likely have a lesion?
right spinothalamic tract lesion, anywhere as it courses lateral brain stem vascular area from medulla to pons to midbrain
57
as neural tube develops, it gives rise to alar and basal plate. compare the two and what happens to their relative positions as fourth ventricle forms
alar plate- develops dorsally, home of sensory neurons
basal plate- develops ventrally, home of motor neurons
when forth ventricle forms, they fan out so alar plate (sensory) is lateral and basal plate (motor) is medial
58
sensory neurons are all ___ located, motor neurons are all ___ located
sensory- lateral
| motor- medial
59
a major component of the alar plates (sensory) migrate ventrally and forms inferior olive, which send its axons....
inferior olive sends axons almost exclusively to cerebellum on opposite side of brain stem
60
the alar plate gives rise to this visceral sensory nucleus that responds to input carried by cranial nerves VII, IX, and X. what is?
solitary nucleus
| cranial nerve VII: facial, IX: hypoglossal, X: vagus, all mixed
61
the (sensory/motor) nuclei give rise to inferior olive, spinal trigeminal nucleus, solitary nucleus, cochlear nucleus, and vestibular nucleus
sensory nuclei (lateral)
62
what relative position do cranial nerves III, IV, VI, and XII exit from brain stem?
medial- the motor cranial nerves
| III- oculomotor, IV- trochlear, VI- abducens, XII- hypoglossal
63
what relative position do cranial nerves V, VII, VIII, IX, and X exit brain stem?
ventral lateral brainstem (all mixed)
| V- trigeminal, VII- facial, VIII- vestibulocochlear, IX- glossopharyngeal, X- vagus
64
what type of nerve is vestibular cochlear nerve, technically speaking?
cranial nerve VIII, technically mixed (but most of its function is sensory)
65
on the dorsal (posterior) side of the lower medulla are a pair of dorsal column nuclei, which form these two nuclei:
dorsal column nuclei of lower medulla form nucleus gracilis (medial) and nucleus cuneatus (lateral) --> site of termination of dorsal columns that ascend bilaterally from spinal cord carrying touch, vibration, proprioceptive sense from limbs and trunk
66
the ___ fibers arise from the gracilis and cuneatus nuclei in the dorsal lower medulla, then cross and coalesce to form the medial lemniscus
internal arcuate fibers- arise from gracilis and cuneatus nuclei, cross midline of lower medulla and form medial lemniscus
67
open medulla sections vs closed medulla section
open medulla section contains fourth ventricle
closed medulla section doesn't have fourth ventricle but has dorsal column nuclei instead (closed medulla section is inferior)
68
this nucleus, buried in the reticular formation in the brain stem, gives rise to motor axons that exit through cranial nerves IX and X (glossopharyngeal and vagus, both mixed)- provide skeletal muscle innervation to muscles of palate, pharynx, larynx. what is?
nucleus ambiguus
| nucleus ambiguous exit through ambiguous, or mixed, cranial nerves
69
solitary tract (brain stem) carries what information?
taste info from solitary nucleus in tongue and epiglottis
70
this region of the brain steam is home to cranial nerves IX, X, and XII, and solitary and vestibular nuclei. what is?
medulla:
cranial nerves: IX (glossopharyngeal, mixed), X (vagus, mixed), XII (hypoglossal, motor)
solitary nuceli: taste
vestibular nuclei: cranial nerve VIII (mixed, but mostly sensory)
71
the ventral aspect of the pons (brain stem) forms a large bulge and stains well with myelin stains. what does it house?
pontine nuclei, sending their axons to overlying cerebellum
72
the only dorsally exiting cranial nerve?
cranial nerve IV- trochlear, motor
all other cranial nerves exit ventrally or ventral laterally
73
this channel runs through the entire length of the midbrain and connects the third ventricle in the diencephalon with the fourth ventricle in the pons/ upper medulla. what is?
cerebral aqueduct
74
the midbrain (brain stem) Edinger-Westphal nuclei contain preganglionic parasympathetic neurons that exit through which cranial nerve?
cranial nerve III, oculomotor (motor)
75
running through the middle of the cerebral peduncles, at the foot of the cerebral cortex, are ___
axons of corticospinal tract
76
in the upper midbrain of the brain stem is the red nucleus, which does what?
modifies cerebellar input and gives rise to axons of rubrospinal tract (upper limb contractions)
77
in the upper midbrain levels of the spinal cord is this structure, which contains dopaminergic neuron cell bodies that project to the basal ganglia. what is?
substantia nigra
these neurons degrade in Parkinson's
78
cadual vs rostral pons sections
caudal = lower pons, contains abducens (VI), facial (VII), vestibulocochlear (VIII)- these are at pontomedullary junction
rostral = upper pons, contains trigeminal nerve (V)
79
the inferior olive is found in the caudal or rostral medulla?
(caudal = lower, rostral = upper)
| inferior olive is in upper (rostral) medulla
80
what are the three medial columns of motor nuclei found in the brain stem?
1. somatic motor- somatic efferent, innervate skeletal muscles of same embryonic origin as limb/trunk muscles
2. visceral motor (parasympathetic)- visceral efferent, preganglionic PNS neurons
3. branchial/pharyngeal arch motor (most lateral)- somatic efferent, but specific to muscles of face/palate/pharynx/larynx
81
what are the four somatic motor nuclei in most medial discontinuous column of brain stem? Where do they exit?
the 4 pure motor cranial nerves that exit from brainstem:
III (oculomotor)- exits at upper (rostral) midbrain
IV (trochlear)- exits at lower (caudal) midbrain
VI (abducens)- exits at lower (caudal) pons
XII (hypoglossal)- exits at upper (rostral) medulla
82
function of oculomotor nucleus (cranial nerve III)
elevate, adduct eye, raise eyelid
83
function of trochlear nucleus (cranial nerve IV)
innervates superior oblique, which depresses and abducts eye
84
what are the four cranial nerves found in the parasympathetic motor column of the brain stem? What are the nuclei that exit with them?
parasympathetic column contains preganglionic PNS neurons, give rise to axons that will exit in cranial nerves:
III (oculomotor)- Edinger Westphal nucleus (constrict pupil), upper midbrain
VII (facial)- superior salivatory nucleus (PNS input to lacrimal gland, salivary gland), lower pons
IX (glossopharyngeal)- inferior salivatory nucleus (secretomotor innervation to parotid gland), lower pons
X (vagus)- dorsal nucleus (PNS input to heart, lungs, gut), lower medulla
85
what are the three nuclei of the pharyngeal arch motor column in the brain stem?
1. trigeminal motor nucleus (cranial nerve V), mastication muscles, exits at upper pons
2. facial nucleus (cranial nerve VII), facial expression, exits at lower pons
3. pharyngeal arch motor nuclei (nucleus ambiguus)- axons exit from both cranial nerves IX (glossopharyngeal) and X (vagus), exits at lower medulla
86
the sensory columns of the brain stem are located laterally to this embryonic division still present in certain parts of the brain stem. what is?
sulcus limitans
87
what are the three sensory columns of nuclei found in the brain stem?
1. solitary nucleus- most medial
2. vestibular nucleus (cranial nerve VIII, vestibulocochlear)
3. trigeminal nucleus (cranial nerve V)- responds to pain/temp, most lateral
88
```
in the sensory columns of nuclei in the brain stem, the rostral (upper) portion of the solitary nucleus responds to ___
the caudal (lower) portion responds to ___
```
rostral solitary nucleus- taste info from cranial nerves VII (facial), IX (glossopharyngeal), and X (vagus)
caudal solitary nucleus- info from carotid sinus (blood pressure receptor) and carotid body (blood chemo receptor), carried by cranial nerves IX and X
89
where do the inferior, middle, and superior cerebellar peduncles arise from in the brain stem?
inferior cerebellar peduncles- medulla
middle cerebellar peduncles- pons
superior cerebellar peduncles- exit from cerebellum and cross in midbrain
90
what is the only prominent nucleus found in caudal (lower) medulla levels?
cranial nerve V (trigeminal) and trigeminal nucleus- carrying pain and temp from ipsilateral face (runs entire length of brain stem, does not exit or enter here- enters/exits at rostral pons)
91
where is the pyramidal decussation found in brain stem?
caudal (lower) medulla
crossing of corticospinal tracts
92
what are the two sets of crossing fibers in the caudal (lower) medulla?
1. pyramidal decussation
| 2. crossing fibers of dorsal column nuclei
93
these two structures in the medulla represent the incoming dorsal roots carrying touch, vibration, pressure, and proprioception from ipsilateral limbs and trunk. what are?
fasciculus gracilis and fasciculus cuneatus
| dorsal column nuclei
94
the fasciculus gracilis and fasciculus cuneatus (dorsal column nuclei) cross over in the upper medulla, forming the ___ which will form the contralateral medial lemniscus
internal arcuate fibers
95
the axons of the inferior olivary nucleus cross the midline of the rostral (upper) medulla and enter the cerebellum via the ___
inferior cerebellar peduncle, which also collects proprioceptive information from spinal cord to send to cerebellum
96
the cranial nerves which enter or exit from the caudal pons are __, ___, ___
cranial nerves VI (abducens, motor), VII (facial, mixed), VIII (vestibulocohlear, sensory)
VII to a lesser degree because it enters at pons-medulla junction
97
the pontine nuclei which form the large ventral bulge of the pons send their axons across the midline to the ____ peduncle on their way to the contralateral side of the cerebellum
middle cerebellar peduncle
98
the cranial nerve loops around the abducens nucleus in the caudal pons (though we're not sure in what direction it loops)
facial nuclei (cranial nerve VII) loops around abducens nuclei (cranial nerve VI)
99
the rostral (upper) pons is the location of the entering/exit fibers of just one cranial nerve. This cranial nerve is mixed. What is the nerve, and what constitutes its motor component?
cranial nerve V (trigeminal) enters/ exits rostral pons
| mostly sensory, but motor component is pharyngeal arch motor (innervates muscles of mastication)
100
what are the 3 divisions of the trigeminal nerve (cranial nerve V)
1. ophthalmic- sensory
2. maxillary- sensory
3. mandibular- sensory and motor root
101
which cerebellar peduncle do the fibers of the trigeminal nerve enter and exit from in the brain stem?
trigeminal nerve enters/exits from rostral (upper) pons (only cranial nerve to enter/exit here)
its fibers go through middle cerebellar peduncle
102
what is the medial longitudinal fasciculus and where is it found in the brainstem (hint: it links two kinds of nuclei)
medial longitudinal fasciculus found in rostral pons
links abducens nucleus neurons in caudal pons with oculomotor nucleus neurons in midbrain
promotes horizontal gaze
103
the midbrain section of the brain stem is the exiting point for which 2 cranial nerves?
III (oculomotor)
IV (trochlear)
both motor
104
what is the fourth ventricle replaced with in the midbrain?
cerebral aqueduct
105
what are the two defining features of a cross section of the midbrain?
cerebral aqueduct
| superior/inferior colliculi
106
where is the first place in the brain stem that the medial lemniscus and spinothalamic tract could be lesioned together?
midbrain, once medial lemniscus finally catches up to lateral position of spinothalamic tract
107
axons projecting out of the cerebellum cross at the superior cerebellar peduncles before ascending up to synapse in thalamus. where is the superior cerebellar peduncle decussation?
lower midbrain of spinal cord
108
where is the trochlear nucleus found specifically in the brain stem?
in midbrain, between the superior and inferior colliculus
(trochlear nucleus is IV, motor)
exits dorsally (only one to do so)
109
this cranial nerve is the only one to completely cross midline and also exit dorsally. It crosses in the inferior medullary vellum before exiting dorsally. what is?
trochlear nucleus, cranial nerve IV (motor)
110
the ocular motor nuclei and the nucleus of Edinger-Westphal (home of preganglionic parasympathetics that exit from cranial nerve III) form a triangular shaped nuclear complex in what region of the brain stem?
upper midbrain
111
the red nucleus is found where in the brain stem and gives rise to what?
upper midbrain
red nucleus gives rise to UMN that form rubrospinal tract (which we think facilitate upper limb flexors)
red nucleus is also site of termination of fibers that travel up to midbrain from superior cerebellar peduncle
gives feedback down to lower medulla, where inferior olivary nucleus is
112
this structure is known as the expressway of the reticular formation, which is the diffuse area found throughout the brain stem. what is?
central tegmental tract
113
what do the neurons of the reticular formation (diffuse area throughout center of brain stem) secrete?
norepinephrine, serotonin
114
the central tegmental tract carries fibers of reticular formation and also ___ in medulla which project up to insular cortex
solitary nucleus (taste fibers)
115
this significant and large nucleus is found in the upper midbrain (ventral and laterally) is functionally associated with the basal ganglia, and is a major source of dopamine. what is?
substantia nigra
