1 - Cerebellum Flashcards
1
Q
Cerebellum functions
A
Regulates equilibrium
Controls muscle tone and posture
Provides motor coordination for voluntary movements
2
Q
Cerebellum
In the near future
A
Plans motor actions in space and time
3
Q
Cerebellum
During execution
A
Monitors ongoing motor activity
Adjusts the output of the motor cortex and several motor nuclei
4
Q
Cerebellum primary function
A
Primary function: Motor adaptation
5
Q
Cerebellum Oversees modification of
A
motor programs in response to the environment
Walking uphill vs. walking on a flat surface
Home field advantage
6
Q
Cerebellum Motor sequence learning is the function of the
A
basal ganglia
In this horizontal section: caudate, putamen, globus pallidus
7
Q
Cerebellum Located in posterior cranial fossa; below
A
tentorium cerebelli
Cortex: Gray matter on the surface
White matter: inside
8
Q
Fissures divide cerebellum in
A
lobes and lobules
9
Q
Fissures: Lobes of the cerebellum
Primary fissure:
A
divides body of cerebellum into anterior and posterior lobes
10
Q
Fissures: lobes of the cerebellum:
Posterolateral fissure:
A
separates flocculonodular lobe from body of cerebellum
11
Q
Cerebellar Deep Nuclei:
Dentate
Contributes
A
most fibers in SCP
12
Q
Cerebellar Deep Nuclei:
A
Interposed nucleus
Emboliform
Globose
13
Q
Cerebellar Deep Nuclei:
A
Fastigal “Frosch Gives Everyone D’s”
14
Q
Three cerebellar peduncles: Interconnect
A
cerebellum and brainstem
15
Q
Three cerebellar peduncles
Inferior cerebellar peduncle
Restiform body:
A
inputs from spinal cord and brainstem; monitors muscle and limb movement
16
Q
Three cerebellar peduncles
Inferior cerebellar peduncle
Juxtarestiform body:
A
interconnects vestibular nuclei and cerebellum
17
Q
Three cerebellar peduncles
Middle cerebellar peduncle (brachium pontis):
A
largest, lateral to pons, afferents from contralateral basis pontis; relays motor signals from cerebral cortex
18
Q
Three cerebellar peduncles: Superior cerebellar peduncle (brachium conjunctivum):
A
mostly efferent fibers to red nucleus and thalamus (VL)
19
Q
Overview of afferents to cerebellar cortex:
Projections:
Vermis:
A
Fastigal
20
Q
Overview of afferents to cerebellar cortex:
Projections:
Medial hemisphere:
A
Interposed
21
Q
Overview of afferents to cerebellar cortex:
Projections:
Lateral hemisphere:
A
Dentate
22
Q
Cerebellar afferents: Spinocerebellar tracts
A
Anterior (superior peduncle)
Posterior (inferior peduncle)
Cuneocerebellar (inferior peduncle)
23
Q
Cerebellar afferents: Trigeminal nerve
A
(uses all 3 peduncles)
24
Q
Cerebellar afferents: Special senses
A
(vision, hearing, vestibular)
Tectocerebellar tract ipsilateral colliculi
Vestibulocerebellar from ipsilateral vestibular nuclei
25
Cerebellar afferents: Pontocerebellar
(middle cerebellar peduncle)
26
Cerebellar afferents: Olivocerebellar
(inferior cerebellar peduncle)
27
Cerebellar afferents: Reticulocerebellar
(paramedian & lateral reticular nuclei in medulla)(inferior cerebellar peduncle)
28
Cerebellar afferents: Serotonergic, noradrenergic:
facilitate transmission in mossy and climbing fibers
29
PSCT origin
Clarke’s nucleus (T1-L2/3)
30
PSCT body part represented
Trunk, leg
31
PSCT Major inputs
Mechanoreceptors in muscles, joints, skin
32
PSCT Midline crossing
None
33
PSCT Peduncle used to enter cerebellum
Inferior
34
ASCT origin
Spinal border cells (T12-L5)
35
ASCT body part represented
Trunk, leg
36
ASCT Major inputs
Mechanoreceptors, movement-related interneurons
37
ASCT Midline Crossing
Twice: First in cord then in cerebellum
38
ASCT Peduncle used to enter cerebellum
Superior
39
CCT origin
Lateral cuneate nucleus in medulla
40
CCT body part represented
Trunk, arm
41
CCT major inputs
Mechanoreceptors in muscles, joints, skin
42
CCT midline crossing
None
43
CCT peduncle used to enter cerebellum
Inferior
44
Olivocerebellar tract: Sensorimotor cortex projects via
corticospinal collaterals onto ipsilateral olivary nuclei
45
Olivocerebellar tract: Olivocerebellar fibers project to
contralateral cerebellar cortex thru ICP
46
Olivocerebellar tract: Inferior olivary nuclei:
posterior lobe
47
Olivocerebellar tract: Accessory olivary nuclei:
anterior lobe (red arrows)
48
Olivocerebellar tract: Climbing fibers: Climbing fibers enter
cerebellum via ICP
49
Olivocerebellar tract: Climbing fibers: Climbing fibers divide into
5-10 branches, synapse as the only climbing fiber on a particular Purkinje cell
50
Olivocerebellar tract: Climbing fibers: Regulate
Purkinje cell firing
51
Olivocerebellar tract: Climbing fibers: ION gets info from
spinal cord (spino-olivary tract), red nucleus, cerebral cortex
52
Olivocerebellar tract: At rest groups of
olivary neurons synchronously discharge, cause complex spikes in Purkinje cells
53
Olivocerebellar tract: Complex spikes:
Occurrence of multiple action potentials in one neuron in response to single action potential from another neuron
54
Olivocerebellar tract: With training performing a motor task
Purkinje cell discharges are simple spikes (produced by parallel fibers)
55
Olivocerebellar tract: If unexpected obstacle to learned motor task is encountered,
complex spikes result each time the obstacle is encountered
56
Olivocerebellar tract: As animal learns to overcome the obstacle,
complex spikes decrease in number and eventually disappear
57
Olivocerebellar tract: Conclusion: Inferior olivary nuclei are involved in
motor learning and in the acquisition of new motor skills
58
Red nucleus: Located in
rostral midbrain
59
Red nucleus: Possible
novelty detector
60
Red nucleus: Input: Collaterals from
Cerebral cortical fibers descending to olive &
Cerebellar output fibers ascending to thalamus
Output: Largest is inhibitory to ipsilateral olivary nucleus
If a mismatch is detected between the intended movement and the movement that is performed then red nucleus may release appropriate olivary neurons, until the two align
61
Red nucleus: Output:
Largest is inhibitory to ipsilateral olivary nucleus
62
Red nucleus: If a mismatch is detected between the
intended movement and the movement that is performed then red nucleus may release appropriate olivary neurons, until the two align
63
juxtarestiform body
(part of inferior cerebellar peduncle that interconnects brainstem and cerebellum and contains mostly vestibular fibers
64
Cerebellar Cortex: Structure:
Uniform throughout
65
Cerebellar Cortex: Structure Three layers:
```
Molecular layer (ML) at top
Purkinje cell layer (arrows)
Granule layer (GL)
```
66
Cerebellar Cortex: Structure: Molecular layer (ML) at top
Contains Purkinje cell dendrites, granule cell axons
67
Cerebellar Cortex: Structure: Purkinje cell layer
Only axons to leave cortex
68
Cortical afferents
excitatory (glutaminergic)
69
Cortical efferents:
inhibitory (GABAnergic)
| Large amount of inhibition in cortical processing
70
Interneurons:
Stellate, Basket and Golgi cells
71
Connectivity of Cortex and Deep Nuclei: Mossy and climbing
fibers send collaterals to deep nuclei before axon enters cortex
72
Connectivity of Cortex and Deep Nuclei: Purkinje cell axons end in
deep nuclei
73
Connectivity of Cortex and Deep Nuclei: Deep nuclei have two
neuronal populations
Source of mossy fibers into cortex
Projection neurons whose axons leave cerebellum
74
A microzone is defined as a group of
Purkinje cells all having the same somatotopic receptive field. Microzones were found to contain on the order of 1000 Purkinje cells each, arranged in a long, narrow strip, oriented perpendicular to the cortical folds
75
Cortical Processing: Mossy fibers excite groups of
granule cells
76
Cortical Processing: Facilitate
many 100s of Purkinje cells (microzone)
77
Cortical Processing: Purkinje cells inhibit clusters of
neurons in deep nuclei
78
Cortical Processing: Weakly facilitated
neurons around edge of microzone are “turned off” by stellate and basket cells (focuses signal)
79
Cortical Processing: Golgi cells in
granule layer inhibit granule cells that initiated signal, turning it off
80
Cerebellar Functional Zones: Cur across
anterior, posterior & flocculonodular lobes
81
Cerebellar Functional Zones: Vermis (V):
In midline
82
Cerebellar Functional Zones Hemispheres:
Medial hemisphere: (adjacent to vermis)
| Lateral hemisphere: Adjacent to medial hemisphere
83
Cerebellum involved in:
Equilibrium
Muscle tone and posture
Coordinating voluntary movements
84
Cerebellar functional zones: So it would make sense for the cerebellum to
receive vestibular, spinal and cerebral cortical input and it does
85
Cerebellar functional zones: The pattern of
inputs underlies the zonal connections to cortex
86
Cerebellar functional zones: Each cerebellar zone is related to a
particular deep nucleus
87
Somatotopic maps in
In anterior and posterior lobes
88
Somatotopic maps: Termed fractionated somatotopy, refers to
fractured nature of body part representation in cortex
89
Vestibulocerebellum
Flocculonodular lobe
Vermis (parts)
Fastigial nucleus
90
Pontocerebellum (Neocerebellum)
Lateral hemisphere projects to dentate nucleus
91
Spinocerebellum
Paravermal (medial hemisphere) area
| Interposed nucleus
92
Vestibulocerebellum: Input:
Vestibular labyrinth
| Vestibular nuclei
93
Vestibulocerebellum: Cerebellar location
Flocculonodular lobe
| Vermis (part of)
94
Vestibulocerebellum: Output:
Fastigial nucleus
Vestibular nuclei
Vestibular nuclei
95
Vestibulocerebellum: Function:
Control of eye movements in response to head movements
| Balance
96
Cerebellar efferents: Vestibulocerebellum: From fastigial nucleus; fibers project to
bilateral vestibular nuclei via ICP with contralateral projection thru cerebellar white matter (uncinate fasciculus)
97
Cerebellar efferents: Vestibulocerebellum: Output to
medial and lateral vestibular nuclei control eyes thru medial longitudinal fasciculus (MLF)
98
Cerebellar efferents: Vestibulocerebellum: Output to ipislateral
lateral vestibular nucleus mediates balancing function of vestibulospinal tract
99
Cerebellar efferents: Vestibulocerebellum: Some Purkinje cell axons don’t
synapse in fastigial nucleus and exert direct tonic inhibition on lateral vestibular nucleus
100
Spinocerebellum: Input:
```
Spinal cord (spinocerebellar tracts)
Brainstem (trigeminal afferents)
```
101
Spinocerebellum: Cerebellar location
Paravermal area
| Vermis (part of)
102
Spinocerebellum: Output:
```
Interposed nucleus
Red nucleus (magnocellular portion)
Rubrospinal and reticulospinal pathways
VA/VL of thalamus
Limb area of primary motor cortex
```
103
Spinocerebellum: Function:
Posture & gait
| Coordination of trunk & limb movements
104
Cerebellar efferents: Spinocerebellum: From interposed nucleus axons leave thru
SCP
105
Cerebellar efferents: Spinocerebellum: Contralateral reticular formation:
those ending in pontomedullary reticular formation regulate function of tectospinal tract in posture and locomotion
106
Cerebellar efferents: Spinocerebellum: Contralateral red nucleus: involved in
motor learning
107
Neocerebellum or Pontocerebellum: Input:
Motor cortex – basilar pons – middle cerebellar peduncle
108
Neocerebellum or Pontocerebellum: Cerebellar location
Lateral cerebellar hemisphere
109
Neocerebellum or Pontocerebellum: Output:
```
Dentate nucleus
Red nucleus (parvocellular portion)
Inferior olivary nucleus
VA/VL of thalamus
All motor cortex & parietal lobe
```
110
Neocerebellum or Pontocerebellum: Function:
| Planning the
timing of movements especially those of the upper extremity
| Coordination of speech
111
Cerebellar efferents: Neocerebellum: From the dentate nucleus; forms
large dentatorubrothalamic tract, which is most of SCP
112
Cerebellar efferents: Neocerebellum: SCP decussates (DSCP) in
caudal midbrain
113
Cerebellar efferents: Neocerebellum: Collaterals to
red nucleus
114
Cerebellar efferents: Neocerebellum: Synapses in
ventral lateral nucleus of thalamus
115
Cerebellar efferents: Neocerebellum: Then information projected by
VL neurons to motor areas of cerebral cortex
116
One side of cerebellum affects ipsilateral side of body
One cerebral hemisphere controls contralateral muscles (corticospinal tract)
117
One half of cerebellum influences
ipsilateral limbs
118
One half of cerebellum projects to
contralateral thalamus
119
Lateral hemispheres:
planning learned, skillful movements, those that become more precise and rapid with practice
120
Injury: Involvement of
arm and speech
121
Intention tremor:
upper extremity shakes as target is approached, hand may overshoot target
122
Dysdiadochokinesia -
rapid alternating movements
123
Dysmetria -
finger-to-nose test
124
Dysarthria -
Uneven phonation (production of vowel sounds) aka scanning or explosive speech
125
Medial hemispheres:
adjusting limb movements
126
Vermis:
postural adjustments
127
Vermis: postural adjustments
Injury: truncal ataxia;
disturbances in balance while seated, also standing and gait ataxia
128
Truncal ataxia: Disrupted
lateral vestibulospinal tract function
129
Gait ataxia:
Anterior lobe lesion (alcoholics); can’t walk without feet wide apart, staggering walk (even when sober)
130
Vestibulocerebellum: Flocculus & vermis important in
eye movements;
| Injury: nystagmus; back and forth eye movements
131
Other functions of the cerebellum: Cognition:
Most lateral aspect of each cerebellar hemisphere indirectly connected with lateral prefrontal cortex in cerebrum
132
Other functions of the cerebellum: Lateral cerebellar activity highest during
speech, most prominent cerebellar activity is unilateral and consistent with dominant frontal cortex (where speech is represented)
More than pure motor control as cerebellar activity higher during functional naming (“drive”, “fly”) rather than object naming (“car”, “airplane”)
133
Other functions of the cerebellum: Strokes:
Cognitive defects: ↓ reasoning power, inattention, grammatical errors, patchy memory loss
Affective defects: dulling of emotional responses, aberrant emotional behaviors
134
Cerebellum has more neurons than
rest of CNS combined
135
Basal ganglia has
pattern for walking
136
Paravermal area
proximal limb and spinal
137
Posterior lobe input
some from spine, most from pons
138
Cerebellar axons don't
leave - synapse in cerebellar nuclei
139
Fastigial nucleus connected
to flocconodular lobe
140
Middle cerebellar peduncle
fibers going in
141
superior cerebellar peduncle
fibers going out
142
Mossy fibers synapse on
granule layer
143
Parallel fibers run
parallel to folia
144
Granule cell turn son
inhibitory transmission
