Basal Ganglia and Cerebellum (W6)
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- Which two components of the Basal Ganglia are referred to as the "Corpus Striatum?"
- Caudate and Putamen
- There are 5 structures that make up the basal ganglia. Name them.
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1. Caudate nucleus
2. Putamen
3. Globus Pallidus
4. Subthalamic nucleus
5. Substantia Nigra - The lenticulate nucleus is made up of which two structures?
-
1. Globus Pallidus
2. Putamen - What are the two divisions of the substantia nigra?
-
pars reticulata
pars compacta - T/F: Basal ganglia have direct access to spinal cord motor neurons.
- FALSE: They must use the thalamus as a "mediator"
- Basal Ganglia structures in relation to the internal capsule: The _________ is located medial to the anterior limb of the internal capsule
- head of the caudate nucleus
- Basal Ganglia structures in relation to the internal capsule: The thalamus is ___________ (med/lat) to the posterior limb of the Internal Capsule.
- Medial
- Basal Ganglia structures in relation to the internal capsule: The putamen and globus pallidus are __________ to the genu and anterior and posterior limbs of the internal capsule
- lateral to the genu and A & P limbs of the internal capsule
- Basal Ganglia structures in relation to the ventricular system: The ______________ forms the lateral wall of the lateral ventricle
- head and body of the caudate nucleus
- Basal Ganglia structures in relation to the ventricular system: The ______________ passes in the roof of the temporal horn of the lateral ventricle.
- tail of the caudate nucleus
- Which basal ganglia structure forms the lateral walls of the third ventricle?
- Thalami
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Basal Ganglia Circuitry:
The _________ connects the cortex afferents to the caudate and putamen. - Internal and External capsule
-
Basal Ganglia Circuitry:
The lenticular fasciculus runs between the ___1________ and ____2____. The last structure runs directly to the ____3_____. -
1. globus pallidus
2. thalamic fasciculus.
3. Thalamus - Which basal ganglia structure is the principal player in determining proper movement?
- Subthalamic Nucleus
- Afferent fibers to the subthalamic nucleus come from? Efferent fibers from the subthalamic nucleus go to?
-
Afferents: GPe (external segment of globus pallidus)
Efferents: GPi (internal segment of the globus pallidus) - Which basal ganglia structure can be functionally lumped together with the globus pallidus?
- SNr (substantia nigra, pars reticulata). Common fiber projection to the thalamus.
- What is the function of the substantia nigra, pars compacta?
- The SNc has dopamininergic neurons: it is an important source of afferents to the caudate and putamen.
- What are the two structures that send afferent fibers to the caudate and putamen (corpus striatum)?
-
1. Cortex
2. SNc (substantia nigra, pars compacta) - The striatum influences the globus pallidus via 2 pathways: name them and describe their course.
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1. Direct pathway -> striatum to GPi (internal segment of globus pallidus)
2. Indirect pathway -> striatum to GPe to Subthalamic nucleus to GPi. - Levels of activity within the subthalamic nucleus appear to be key in controlling _________________.
- the initiation of movement
- All output from the striatum can be classified as __________.
- Inhibitory (via GABA)
- D1 receptors are ___________ and are mainly associated with which pathway? What about D2 receptors?
-
D1 -> inhibitory, associated with indirect pathway
D2 -> excitatory, associated with direct pathway - What type of interneurons does the striatum contain? are they (+) or (-)?
- cholinergic interneurons (use acetylcholine). (+)
-
Define:
1. akinesia
2. rigidity
3. tremors -
1. loss of the power of voluntary movement. slow to initiate movement
2. resistance to passive movement, stiffness
3. involuntary trembling -
Define:
1. Chorea
2. Athetosis
3. Ballism -
1. dance-like involuntary mvmts. of the limbs
2. slow involuntary writhing mvmnt. of fingers & hands.
3. violent jerking or shaking mvmnt. of the limbs - Parkinson's disease is caused by ______________. Describe the state of a brain afflicted with PD.
-
intrastriatal dopamine depletion.
nigro-striatal dopaminergic projections degenerate, pars compacta depigmented. - What type of reflexes would a patient with PD have?
- Normal reflexes
- Huntington's disease is caused by ___________. What is observed in this brain?
- caused by intrastriatal GABA depletion due to degeneration of the striatum. Cortical atrophy is observed
- Describe the activity of the subthalamic nucleus in a PD patient versus an HD patient
-
PD -> subthalamic nuclei neurons are more active
HD -> subthalamic nuclei neurons are less active - What would cause hemiballismus?
- a subthalamic stroke. One subthalamic nucleus is obliterated resulting in contralateral hemiballismus
- What is the inheritance of Huntington's disease?
- autosomal dominant
- The thalamus can be divided into 3 main portions when viewed from above. Name them. What separates these?
-
1. Anterior
2. Medial
3. Lateral
internal medullary lamina separates the portions. (white matter) - When the thalamus is viewed from the lateral side there are 5 divisions in the ventral tier. Name them.
-
1. Medial Geniculate Body
2. Lateral Geniculate Body
3. Ventral Posterior Nucleus
4. Ventral Lateral Nucleus
5. Ventral Anterior Nucleus - The medial geniculate body mediates _________ afferents, while the lateral geniculate nucleus mediates ______ efferents.
-
auditory
visual - Which portion of the thalamus are the VPL and VPM found in?
- Ventral Posterior Nucleus
- In which portion of the thalamus are cerebellum efferents and basal ganglia afferents found?
- VLN (Ventral Lateral Nucleus)
- In which portion of the thalamus are some of the basal ganglia afferents found?
- VAN (Ventral Anterior Nucleus)
- In which portion of the thalamus are somatosensory afferents found?
- VPN (Ventral Posterior Nucleus)
- Why has the cerebellum been called a "comparator?"
- Because it compensates for errors in voluntary mvmnts. by comparing intention (from cortex) with performance (from ascending sensory systems)
- Where is the vermis of the cerebellum found?
- In the midline (vermis means worm, therefore the vermis looks like a worm)
- There are 3 lobes of the cerebellum. Name them
-
1. Anterior lobe
2. Posterior lobe
3. Flocculonodular lobe - Which fissure separates the anterior lobe from the posterior lobe in the cerebellum?
- The primary fissure
- Which fissure separates the posterior lobe from the flocculonodular node?
- The posterolateral fissure
- The inferior cerebellar peduncle connects the __________ to the cerebellum.
- medulla and spinal cord
- The middle cerebellar peduncle connects the _________ to the cerebellum.
- basilar (ventral) pons
- The superior cerebellar peduncle connects the cerebellum to the ________.
- midbrain and thalamus
- Which cerebellar peduncles contain efferent and afferent fibers?
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1. Inferior and Middle Peduncles -> afferent
2. Superior peduncle -> efferent - The cerebellum is divided into 3 functional subdivisions. Name them
-
1. vestibulocerebellum (flocculonodular lobe)
2. spinocerebellum (medial)
3. cerebrocerebellum (lateral) - What is the function of the vestibulocerebellum?
- governs eye movements and equilibrium during stance and gait
- What is the function of the spinocerebellum?
- controls posture and gross coordination
- What is the function of the cerebrocerebellum?
- coordinates refined or skilled movements
- A lesion in which portion of the cerebellum would result in nystagmus?
- vestibulocerebellum - lesion manifests as vestibular symptoms
- What is the arbor vitae?
- "tree of life," the internal white matter of the cerebellum
- There are 3 cortical layers of the cerebellum. Name them from outside to in.
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1. Molecular layer (mostly fibers)
2. Purkinje cell layer
3. Granule cell layer - There are 4 pairs of deep nuclei in the cerebellum. Name them from lateral to medial.
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1. Dentate
2. Emboliform
3. Globose
4. Fastigal
"Don't Eat Greasy Food" - Which 2 deep nuclei of the cerebellum are often combined and known as "interposed nuclei?"
- emboliform and globose nuclei
- Which nuclei of the cerebellum are associated with the spinocerebellum? How about the cerebrocerebellum?
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Spinocerebellum -> Emboliform, Globose, Fastigal
Cerebrocerebellum -> Dentate - A cerebellar hemisphere recieves ascending sensory information from the ___________ side of the body. (ipsi/contra)
- ipsilateral
- A cerebellar hemisphere recieves motor command information from the __________ cortex. (ipsi/contra)
-
contralateral
it is then relayed and decussates at the pons. - a cerebellar hemisphere sends information back to the _______ motor cortex via the thalamus. (ipsi/contra)
- contralateral
- a cerebellar hemisphere is responsible for regulation of movement on the ________ side of the body. (ipsi/contra)
- ipsilateral
- Name the 2 cerebellar afferent pathways to the cerebrocerebellum.
-
1. pontocerebellar fibers
2. olivocerebellar fibers - How do pontocerebellar fibers get to the cerebrocerebellum? What kind of information do they carry?
- via the middle cerebellar peduncle. they carry information from sensory and motor cortices.
- the pontocerebellar fibers recieve information from the cortex __________, then they project fibers _________ to the cerebrocerebellum. (ipsi/contra)
-
recieve ipsilaterally
project contralaterally - What information do the olivocerebellar fibers transmit?
- info from spinal cord, brainstem and cortical sources
- Describe the pathway of the olivocerebellar fibers.
- from inferior olivary nucleus (which recieves and integrates info) to the contralateral cerebellar cortex via the inferior cerebellar peduncle
- There are 5 afferent pathways that end in the spinocerebellum. Name them.
-
1. DSCT
2. Cuneocerebellar tract
3. VSCT
4. Olivocerebellar fibers
5. Trigeminocerebellar fibers - The DSCT, cuneocerebellar, olivocerebellar and trigeminocerebellar all project to the spinocerebellum via the ____________.
- inferior cerebellar peduncle
- The VSCT projects to the spinocerebellum via the ____________.
- superior cerebellar peduncle
- There are 2 pathways that project onto the vestibulocerebellum. Name them.
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1. vestibulocerebellar fibers
2. olivocerebellar fibers - There are two kinds of vestibulocerebellar fibers. What are they called and what is the difference?
- 1. primary vestibulocerebellar afferents bypass vestibular nuclei & go directly to cerebellum. Secondary vestibulocerebellar afferents go through the nuclei
- How do the vestibulocerebellar fibers project to the vestibulocerebellum?
- via the juxtarestiform body
- Purkinje cells are ___________(+) or (-). Which neurotransmitter do they release?
-
(-) inhibitory
release GABA - Purkinje cells are large: they are the primary way from the ____________ to the _____________.
- cerebellar cortex to the deep nuclei
- Purkinje neurons of the flocculonodular lobe project to the _____________ via the _____________.
-
lateral vestibular nucleus
juxtarestiform body - Climbing fibers come from the ___________ and are ___ (+) or (-) to Purkinje cells and deep nuclei.
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inferior olive
(+) - Mossy fibers come from __________ and are (+) to the ________ and _________.
-
everywhere but the inferior olive
deep nuclei and granule cells - The fastigal nucleus recieves input from the Purkinje neurons and projects ____1___ to the ____2____ via the ___3_____.
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1. bilaterally
2. vestibular complex
3. juxtarestiform body - The Globose, Emboliform & Dentate nuclei all recieve input from Purkinje cells and project to the ____1____ and _____2____ via the ______3__.
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1. red nucleus
2. ventrolateral thalamic nucleus
3. superior cerebellar peduncle - Define: ataxia
- inability to coordinate the muscles in voluntary movement (catch all term)
- Define: past pointing
- a systemic drift (to one side) of a directed movement. This is a vestibulocerebellar symptom
- What type of tremor is specific to cerebellar disorders?
- intention tremor
- Define: dysmetria
- inability to stop a mvmt at a desired point. (reach for coffee cup on table can't stop)
- Define: decomposition of movements
- movements broken down into its constituent parts
- Define: dysdiadochokinesia
- inability to perform rapid alternating movements
- What is masking of cerebellar signs?
- When there is a lesion in a cerebellar pathway but it is hidden in a CST lesion. (ie. paralysis)