Lecture 13: Cerebellum Flashcards
1
Q
What is the largest part of the hindbrain?
A
The cerebellum
2
Q
What sits in the Posterior Cranial Fossa?
A
The Cerebellum
3
Q
Where in the skull does the cerebellum sit?
A
In the posterior cranial fossa
4
Q
What part of the dura does surrounds the dura mater?
A
The tentorium cerebelli
5
Q
What sits under the tentorium cerebelli?
A
The cerebellum
6
Q
What forms 2/3 walls of the fourth ventricle?
A
The cerebellum
7
Q
What is the fourth ventricle surrounded by?
A
CSF
8
Q
How does the CSF get to the cerebellum?
A
Through the median and lateral aperatures
9
Q
What is the Cisterna Magna?
A
The big CSF cistern that allows CSF to reach the subarachnoid space
10
Q
How does the cerebellum connect to the Brainstem?
A
Via the three peduncles
11
Q
What percent of brain volume and neurons is the cerebellum?
A
10% of total brain volume; >50% of neurons
12
Q
What is the overall purpose of the cerebellum?
A
It is the overall consultant on rapid movement - keeps the stride steady and balanced
13
Q
Where does the cerebellum provide input to?
A
The Thalamus and the Cortex
14
Q
What kind of input does the cerebellum receive?
A
Afferent input from all muscles and joints
15
Q
Why does the cerebellum receive afferent input from all muscles and joints?
A
Because it needs to know where muscles and joints are in space before performing a function
16
Q
What does the cerebellum consult on?
A
Rapid and ongoing movements to tweak motor skills
17
Q
Where does the efferent information coming from the cerebellum need to go before reaching the cortex?
A
The thalamus
18
Q
What does Cerebellum mean?
A
Little brain
19
Q
What is the cerebellum considered part of the motor system?
A
Because if the cerebellum is damaged movement is still possible but the patient has deficits
20
Q
What deficits may a patients have if the cerebellum is damaged?
A
- Gait imbalance, poor postural control
- Poor coordination of voluntary movements ex. Slurred speech or tremor when moving
21
Q
Why are there deficits when the cerebellum is damaged?
A
Because the cerebellum, basal ganglia and motor systems are disinhibiting to all for motor movement
22
Q
What happens to people with cerebellar damage when performing intentional motor movements?
A
They have a tremor
23
Q
Why do people with cerebellar damage have a tremor when performing intentional motor movements?
A
Because the cerebellum is no longer inhibiting extraneous motor movement
24
Q
What are the functions of the cerebellum?
A
- Controls equilibrium/balance
- Controls posture and muscle tone
- Coordinates smooth and purposeful movement
25
How does the cerebellum control equilibrium and balance?
By using the vestibular pathway using information from the inner ear to control core musculature to balance
26
Is the cerebellum involved in sensory processing?
Yes, the cerebellum is a huge sensory processor
27
What is meant by the cerebellum is the great comparator?
It compares cortical command with muscle and joint positioning and tone
28
Through what tracts does the cerebellum compare muscle joint positioning and tone?
The ipsilateral spinocerebellar tracts (and cuneocerebellar tracts)
29
What are the spinocerebellar tracts and cuneocerebellar tracts?
Sensory afferents from all the muscles, joints and tendons from one side of the body that go to the ipsilateral side of the cerebellum
30
After receiving ipsilateral information from the spinocerebellar tracts what does the cerebellum do?
Sends information through the thalamus to and advises the cortex on how much, how many, and how fast
31
What happens after the cerebellum advises the cortex on a movement?
The motor cortex sends the revised command down the corticospinal tract
32
What are the three steps in the cerebellum being a comparator?
1. Receives muscle and joint positioning from spinocerebellar tracts
2. Advises the cortex on how much, how many and how fast
3. Motor cortex sends the revised command down the corticospinal tract
33
How many afferent tracts does the cerebellum receive?
Two afferent tracts
34
What are the two afferent tracts that the cerebellum receives?
The Corticopontocerebellar tract and the spinocerebellar tracts (ipsilateral)
35
What are the corticopontocerebellar tracts?
Axon tracts from the premotor and supplementary motor cortex that connects to the cerebellum
36
What is the pathway of the Corticopontocerebellar tracts?
1. Premotor cortex/supplementary motor cortex to the pons
2. Pons through the middle cerebellar peduncle to the cerebellum
37
Which cerebellar peduncle doe the corticopontocerebellar tract travel through?
The Middle Cerebellar Peduncle (MCP)
38
What tract travels through the middle cerebellar peduncle?
The Corticopontocerebellar tract
39
Where does the Corticopontocerebellar tract synapse?
At the pons and cerebellum
40
What is the pathway of the Spinocerebellar tracts?
They go from the upper and lower limbs (muscle spindles and tendon organs) to the cerebellum through the inferior cerebellar peduncle (ICP)
41
What is the neuron pathway of the spincerebellar tracts?
1. From muscle, joints and tendons they synapse at the spinal cord (at the dorsal nucleus of Clarke)
2. From the spinal cord through the inferior cerebellar peduncle to the cerebellum
42
Where does the spinocerebellar tract synapse?
At the spinal cord (dorsal nucleus of Clarke) and cerebellum
43
Which pathway travels through the inferior cerebellar peduncle (ICP)?
The spinocerebellar tracts
44
Which peduncle does the spinocerebellar tract travel through?
The inferior cerebellar peduncle (ICP)
45
Which pathway travels through the middle and inferior cerebellar peduncles?
Middle Cerebellar Peduncle - Corticopontocerebellar tract
Inferior Cerebellar Peduncle - Spinocerebellar Tracts
46
What are the two dorsal spinocerebellar tracts?
- Spinocerebellar tract (lower limbs)
- Cuneocerebellar tract (upper limbs)
47
What do the spinocerebellar tracts sense?
Muscle spindles, tendons and tendon organs
48
What are the largest peripheral nerves?
The dorsal spinocerebellar tracts and cuneocerebellar tracts
49
What happens as a result of the spinocerebellar and cuneocerebellar axons being large?
They are the most myelinates and as a result they are faster than motor axons so they can adjust for sensory axons to advise motor axons
50
What synapses at the Dorsal Nucleus of Clarke?
The spinocerebellar and cuneocerebellar tracts
51
What happens when an individual is thinking about a movement?
The premotor and supplementary motor cortices send afferents down to the basal ganglia and cerebellum
52
What happens after the premotor and supplementary motor cortex sends afferents down to the basal ganglia and cerebellum?
The cerebellum processes this information and sends information back to the upper motor cortex to tell which muscles to contract or not to contract
53
Why is the middle cerebellar peduncle so big?
Because there are tons of afferent motor fibers from from the motor cortex to the cerebellum
54
What kind of afferents does the cerebellum receive?
Motor and sensory afferents
55
What do the motor afferents that the cerebellum receives refer to?
Information from the motor planning areas
56
What kind of sensory afferents does the cerebellum receive?
Afferent information from joints and muscle spindles
57
What side would a lesion to the cerebellum cause deficits?
Ipsilaterally
58
When advising the cortex, which side does the cerebellum project to?
It projects contralaterally
59
Why is a lesion to the cerebellum contralateral?
1. The cerebellum receives cortical information from the contralateral side of the cortex
2. The cerebellum sends information back to the contralateral side of the cortex
3. The crotex then projects to muscles on the contralateral side
This means that there is a double crossover
60
What is the other name for the Lateral Corticospinal Tract?
Pyramidal Tract
61
What happens in the cerebellum once a movement is evoked?
The cerebellum continues to compare the movement that it tried to tell the muscle to do and corrects for errors
62
Where does the Corticospinal tract synapse and cross over?
It crosses over at the medulla and synapses at the spinal cord
63
How is the cerebellum continuously involved in ongoing movements?
The cerebellum compares the intended movement with actual movement and corrects for errors as the movement evolves in real time
64
What are five cerebellar disorders?
Ataxia
Dysmetria
Dysdiadochokinesia
Forces 'intentional tremor'
Vertigo
65
What is Ataxia?
Lack of coordination of muscle movements
66
What can Ataxia look like?
Awkwardness of posture and gait
67
What does Awkwardness of posture and gait usually mean for the cerebellum?
There is a lesion to the midline cerebellum
68
What is an ipsilateral cerebellar sign?
When there is a tendency to fall to the same side as a lesion
69
What are two types of Ataxia?
Dysmetria
Dysdiadochokinesia
70
What is Dysmetria?
Overshooting a goal in reaching for a target
71
What is Dysdiadochokinesia?
Inability to perform rapid alternating movements
72
What is is called when overshooting a goal in reaching for a target?
Dysmetria
73
What is it called when a person in unable to perform rapid alternating movements?
Dysdiadochokinesia
74
What is a Forced Intentional tremor?
When an individual has a tremor when attempting to perform purposeful movements
75
What usually causes resting tremors?
Basal Ganglia lesions
76
What is the foliage of the cerebellum?
The folds of the cerebellum
77
What are the spaces between folia called?
Fissures
78
What do Primary Fissures in the cerebellum do?
Divides the cerebellum into lobes
79
What is the Vermis?
The midline of the cerebellum
80
What is the midlines of the cerebellum called?
The Vermis
81
How many blood vessels supply the cerebellum?
Three
82
What are the blood vessels that supply the cerebellum?
1. Superior cerebellar artery
2. Anterior Inferior Cerebellar Artery (AICA)
3. Posterior Inferior Cerebellar Artery (PICA)
83
How many peduncles does the cerebellum have?
Three
84
How many lobes does the cerebellum have?
Three
85
How many deep nuclei does the cerebellum have?
Three
86
How many layers of cells does the cerebellum have?
Three
87
How many functional divisions does the cerebellum have?
Three
88
What are the three cerebellar peduncles?
- Superior cerebellar peduncle
- Middle cerebellar peduncle
- Inferior cerebellar peduncle
89
What are the afferent and efferent classifications of the cerebellar peduncles?
- Superior cerebellar peduncle (mostly efferent)
- Middle cerebellar peduncle (afferent)
- Inferior cerebellar peduncle (afferent)
90
What does the Inferior Cerebellar Peduncle do?
Carries information from the spinal cord and medulla going to the cerebellum - spinocerebellar tracts
91
What does the Middles Cerebellar Peduncle do?
Carries information from the motor cortex for motor planning from the through the pontine nuclei to the cerebellum
92
What does the superior cerebellar peduncle do?
Carries information from the cerebellum going to the midbrain, thalamus and ultimately the frontal lobe
93
What is the Dentatothalamocortical tract?
The tract that carries information from the cerebellum to the motor cortex to tell it which UMNs to activate and inhibit
94
What is the pathway of the Dentatothalamocortical tract?
Cerebellum through superior cerebellar peduncle to midbrain and thalamus to the primary motor cortex
95
What are the three lobes of the cerebellum?
1. Anterior Lobe
2. Posterior Lobe (includes tonsil)
3. Flocculonodular Lobe
96
What happens if there is swelling or space-filling lesions in the brain?
It can cause the cerebellar tonsil to herniate and this is where the nucleus of the solitary tract and cardiorespiratory centers are and they get damaged
97
Describe the cerebellar homunculus?
- The midline structures are in the middle of the cerebellum
- The shoulder and hip are lateral
- Farther lateral are the distal limbs
- The distal part of the cerebellum is associated with fingers, toes, legs and arms
- Middle part is core and truncal stability
98
What are the sizes of the anterior and posterior lobe of the cerebellum?
There is a smaller anterior lobe and a larger posterior lobe
99
What is the Vermis made of?
The Anterior lobe, posterior lobe and the nodule
100
What is the Flocculonodular lobe made of?
The Flocculus and Nodule
101
What are the afferent tracts to the cerebellum?
- Corticopontocerebellar tracts
- Spinocerebellar tracts
- Vestibulocerebellar tracts
102
Through what does the cerebellum project to the motor areas?
Via the deep cerebellar nuclei (GABA)
103
What is found deep in the cerebellum?
Deep cerebellar nuclei
104
What are the inputs to the cerebellum classifed as?
Climbing fibers or mossy fibers
105
What are Climbing fibers?
Any afferent fibers involving the olive
106
What kind of fibers are Dorsal cerebellar and cuneocerebellar tracts (mossy/climbing)?
They are mossy fibers
107
What are the three important afferents to the cerebellar cortex?
- Corticopontocerebellar tracts
- Dorsal Spinocerebellar and cuneocerebellar tracts
- Vestibulocerebellar tracts
108
What are the vestibulocerebellar tracts?
Tracts that sense when the head move in space and allows for truncal stability via the cerebellum
109
What neurotransmitter do the three afferent pathways to the cerebellum release?
Glutamate. Meaning that the cerebellum receives glutamatergic afferents
110
What kind of afferents does the cerebellum receive (neurotransmitter)?
Glutamatergic afferents
111
What kind of neuron is the output neuron from the cerebellum?
The Purkinje neuron
112
What happens if there is enough glutamate from the afferents to activate an output purkinje neuron in the cerebellum?
The output neuron from the cerebellum (purkinje neuron) will send GABA (an inhibitory neurotransmitter) to the deep cerebellar nuclei
113
What causes the cerebellum Purkinje neuron to release GABA onto the deep cerebellar nuclei?
The release of glutamate from afferent fibers onto the cerebellum
114
What does the GABA released onto the deep cerebellar nuclei do?
Inhibits the three deep cerebellar nuclei
115
When there is no GABA being released onto the deep cerebellar nuclei by the Purkinje neurons what do the deep cerebellar nuclei do?
They fire GABA onto the thalamus
116
What happens when the Purkinje neurons fire GABA onto the deep cerebellar nuclei?
They inhibit the deep cerebellar nuclei from firing GABA onto the thalamus
117
What happens when GABA is released onto the thalamus?
It inhibits movement
118
What are the steps starting from afferent fibers releasing glutamate onto cerebellum neurons?
1. Afferent fibres release glutamate onto cerebellar neurons
2. This cause Purkinje cells to be activated and release GABA onto the deep cerebellar nuclei
3. The deep cerebellar nuclei then stop releasing GABA onto the thalamus
4. This disinhibits the thalamus allowing it to fire to the cortex allow for movement
119
How is the thalamus disinhibited?
The deep cerebellar nuclei stop releasing GABA onto the thalamus because Purkinje fibers are releasing GABA onto the deep cerebellar nuclei because they are activated by glutamate released from afferent fibers
120
What are the three layers of the cerebellar cortex from outside to inside?
- Molecular Layer
- Purkinje cell Layer
- Granule cell Layer
121
What do the afferents release on the cerebellum?
Glutamate
122
What do the Purkinje cells release onto the Deep Cerebellar Nuclei?
GABA
123
What do deep cerebellar nuclei release onto the thalamus?
GABA
124
Describe Purkinje cells?
They have a large dendritic arbour and unmyelinated cytoplasmic processes that reach into the molecule cell layer
125
Where do Purkinje cell axons go?
They transverse the granule cell layer and reach the molecular cell layer and sends axon tracts down to the deep cerebellar nuclei
126
How many dendrites and axons do Purkinje cells have?
They have many dendrites but one axon
127
What acts on Purkinje cell neurons to tell them whether to fire or not onto deep cerebellar nuclei?
Afferents from the granule cell layer
128
What happens if Purkinje neurons are activated by glutamate?
They release GABA onto deep cerebellar nuclei
129
What is the outer cell layer in the cerebellum?
Molecular cell layer
130
What is the middle cell layer in the cerebellum?
Purkinje cell layer
131
What is the inner cell layer in the cerebellum?
The granule cell layer
132
What cells do all the afferent pathways to the cerebellum act on?
Granule cells
133
What kind of fibres synapse on granule cells?
Mossy fibers
134
What do mossy fibers synapse on?
Granule cells
135
What pathways do the mossy fibers come from?
- Dorsal spinocerebellar and cuneocerebellar tracts
- Vestibular cerebellar tracts
- Pontocerebellar tracts
136
What do the mossy fibres release onto granule cells?
Glutamate
137
Where do granule cells project?
They protect through the granule cell layer into the molecular layer where purkinje dendrites are
138
What do Granule cells synapse on?
Purkinje cells (parallel fibers)
139
What synapses onto Purkinje cells?
Granule cells and climbing fibers
140
What is the pathway of climbing fibers?
They climb pass the granule cells and synapse directly onto purkinje cells
141
What do climbing fibers release onto purkinje cells?
Glutamate
142
Where do climbing fibers come from?
They come from the olive
143
What activate purkinje cells?
Climbing fibers and granule cells activated by mossy fibers releasing glutamate on them
144
Where do Purkinje cells project to?
Deep cerebellar nuclei
145
What do purkinje cells release?
GABA onto deep cerebellar nuclei to prevent them from releasing GABA onto the thalamus
146
Through which peduncle do olivocerebellar fibers (climbing fibers) enter the cerebellum?
Through the Inferior Cerebellar Peduncle
147
What is the pathway of Olivocerebellar fibers?
Inferior olive - cross midline - enter cerebellum through inferior cerebellar peduncle - synapse directly onto molecule layer (purkinje cell dendrite)
148
Are mossy fibers excitatory or inhibitory?
They are excitatory
149
What are the three mossy fiber tracts?
- Spinocerebellar + Cuneocerebellar
- Corticopontocerebellar
- Vestibularcerebellar
150
What is the pathway of mossy fibers?
Synapse onto granule cell layer - Granule cell axons project to molecular layer - They synapse onto Purkinje cells dendrites - Project to deep cerebellar nuclei
151
What are the efferent axons of the cerebellum?
The deep cerebellar nuclei
152
What do Purkinje cells do for the deep cerebellar nuclei?
They fine-tune impulses of the deep cerebellar nuclei
153
What happens with the mossy and climbing fibers during rest?
They act directly onto the deep cerebellar nuclei and release glutamate on them to allow them to continue release GABA onto the thalamus to inhibit activation
154
Why do Purkinje cells only fine tune the deep cerebellar nuclei?
Because the deep cerebellar nuclei already receive excitatory inputs from the mossy and climbing fibers
155
What are the three deep cerebellar nuclei?
- Fastigial nucleus
- Interposed nucleus
- Dentate nucleus
156
Where is the Fastigial nucleus in the cerebellum?
In the vermis
157
What is the Fastigial nucleus important for?
Balance and posture
158
Which cerebellar nucleus is important for balance and posture?
The Fastigial Nucleus
159
What is the Interposed Nucleus composed of?
The Globose Nucleus and the Emboliform nucleus
160
What do the Globose and Emboliform nucleus make?
The Interposed nucelus
161
Where is the interposed nucleus found?
In the Paravermal zone
162
What does the interposed nucleus control?
The trunk, shoulder, hips and proximal limb muscles
163
Where is the dentate nucleus located?
In the Lateral zone
164
What does the Dentate nucleus control?
Distal limb muscles
165
What area is each cerebellar nucleus located?
Fastigial nucleus - Vermis
Interposed nucleus - Paravermal zone
Dentate nucleus - Lateral zone
166
What nucleus controls the trunk, shoulder hips and proximal limb muscles?
Interposed
167
What nucleus controls the distal limb muscles?
Dentate nucleus
168
Which tracts does the Fastigial Nucleus give input to?
The vestibulospinal and Reticulospinal
169
Which tracts do the Interpositus nucleus give input to?
- Corticospinal tract
- Corticobulbar tract
- Rubrospinal tract
170
Where does the dentate nucleus give input to?
- VA/VL thalamus to Motor, Premotor and supplementary motor cortex?
171
What control does the Fastigial Nucleus have?
- Modulate balance and truncal stability
- Muscle tone
172
What control does the Interpositus Nucleus have?
- Execution of movement
- Modulate movement
173
What control does the Dentate Nucleus have?
- Motor planning
- Evaluation of sensory information
174
What nuclei is in the Flocculonodular lobe?
The Vestibular nuclei
175
What area of the cerebellum is the Vestibular Nuclei?
The Flocculonodular lobe
176
What is the big motor planning area in the cerebellum?
The lateral zone
177
What coordinates eye and head movements in the cerebellum?
The focculonodula lobe in connection with the vestibular nuclei
178
What do the Fastigial nucleus and Interposed nucleus do together?
- Maintain axial balance
- Maintain muscle tone and synergy of collaborating muscles
179
What does the dentate nucleus mainly do?
- Motor planning
- Evaluation of sensory info
- Ensure smooth sequence of muscle contractions and precision of force, direction and extent of voluntary upper movements
180
What does the Vestibular nuclei mainly do?
- Coordinated muscles of balance equilibrium
- Coordinates head and eye movements
181
What is the Dentatothalamocortical tract?
The projection pathway from the thalamus to the motor planning areas of the cortex
182
What is the projection pathway from the thalamus to the motor planning areas of the cortex?
The Dentatothalamocortical tract
183
What are the major cerebellar efferent pathways?
The Dentatothalamocortical tract and the Vestibulospinal Tract
184
What peduncle does the Dentatothalamocortical tract pass through?
The Superior Cerebellar peduncle
185
What are the three functional divisions of the Cerebellum?
Flocculonodular lobe - controls equilibrium/balance
Vermal/Paravermal zone - controls posture and muscle tone
Lateral Zone - Coordinates smooth purposeful movements
186
How does the Vestibulocerebellar tract work?
1. Projects to granule neurons b/c they are mossy fibers
2. Granule neurons synapse onto purkinje neuron dendrites
3. They synapse of the Fastigial nuclei which project to the vestibular nuclei in the brainstem
4. Vestibular nucleus send axons to excite arm/leg extensors for balance and axial core muscles
