Lecture 14: Basal Ganglia Flashcards
What are the functions of the basal ganglia?
- Release appropriate movements from premotor and motor areas
- Allows a smooth motion that is planned an purposeful without extraneous movements
- Allows appropriate movement to start and stop
What are the functions of the cerebellum?
- Modulate cortical output
- Controls the maintenance of equilibrium, posture and muscle tone
- Coordinates movements (and corrects for errors in movements)
How does the cerebellum modulate cortical output?
It gets information from the cortex, forms a plan and sends a signal back to the premotor cortex
What tracts does the cerebellum coordinate conscious movements for?
Corticospinal and Corticobulbar tracts
What is the Corticopontocerebellar pathway?
The pathway that descends from the premotor or supplementary motor cortex when we want to make a conscious movement
What is the pathway that allows motor planning information to enter the cerebeelum?
The Corticopontocerebellar pathway
Which peduncle does the Corticopontocerebellar pathway enter the cerebellum?
The middle cerebellar peduncle
What tract enters the middle cerebellar peduncle?
The corticopontocerebellar pathway
What does the Corticopontocerebellar pathway descend onto?
Granule cells
Why does the Corticopontocerebellar pathway descend onto Granule cells?
Because it is a mossy fiber
Is the Corticopontocerebellar pathway a mossy or climbing fibers?
It is a mossy fiber and descends on Granule cells
What happens after the corticopontocerebellar pathway descends on Granule cells?
It activates glutamatergic signaling to activate purkinje cells
What cells do Granule cells activate with glutamate?
Purkinje cells
Where does the cerebellum project to after receiving motor planning information?
It projects to the contralateral cortex via the thalamus
Which side of the cortex does the cerebellum send and receive motor plans?
It sends and receives motor plans to and from the contralateral cortex
Which side of the cortex does the basal ganglia project to?
The ipsilateral side of the cortex
Which nucleus in the thalamus does the cerebellum and basal ganglia project to?
The VA/VL nucleus
What does the basal ganglia allow for?
It allows for movements to be initiated and helps to plan for the best movement by tweaking movements in real time
If there is a lesion to the cerebellum, where would the effect be seen?
On the ipsilateral side because the corticospinal tract crosses over
What are the two different pathways of the basal ganglia?
- Indirect pathway
- Direct pathway
What nucleus in the the thalamus do both basal ganglia pathways act on?
The VA/VL nucleus
Where does the basal ganglia receive input from?
The premotor cortex (premotor cortex also acts on the cerebellum)
What will the direct or indirect pathway of the basal ganglia do?
They will either inhibit the thalamus and decrease movement or not inhibit the thalamus and promote movement
What can Cerebellar lesions cause?
- Cerebellar ataxia
- Forced Tremor
- Inability to coordinate smooth purposeful movement
What lesion would cause:
- Cerebellar ataxia
- Forced Tremor
- Inability to coordinate smooth purposeful movement
A cerebellar lesion
What is Cerebellar ataxia?
The lack of coordination of muscle movements
What is a forced tremor?
When there is no tremor at rest but there is a tremor when performing movements
What are some smooth purposeful movements that are difficult with a cerebellar lesions?
- Repetitive movement
- Finger to nose test (overshoot)
- Heel to shin test (can’t move smoothly)
What diseases can lesions to the Basal Ganglia cause?
- Parkinson’s disease (PD)
- Huntington’s disease (HD)
What parts of the brain are Parkinson’s and Huntington’s disease associated with?
The basal ganglia
What are the symptoms fo Parkinson’s disease?
- Bradykinesia (slowness of movements)
- Fine tremor at rest
- Pill rolling tremor
- Poverty of movement
How do people with Parkinson’s tend to walk?
They tend to lean forward to initiate walking because they are unable to do this due to damaged basal ganglia
What are the symptoms of Huntington’s Disease?
- Involuntary flinging and flailing of movements (chorea)
- Too much movement
What does the Postmortem brain of Huntington’s disease patients look like?
Lesions in basal ganglia (cell death and degeneration)
What does the Postmortem brain of Parkinson’s disease patients look like?
A decreased size of the substantia nigra
What does the Basal Ganglia have a major role in?
The control of normal voluntary movement
Where does the basal ganglia receive constant input from?
The cerebral cortex, muscle spindles and joints about the location and posture of the body
Where does the basal ganglia send outputs to?
The prefrontal, premotor and primary motor cortices via the thalamus
What causes Huntington’s disease?
Cell death in the caudate nucleus of the basal ganglia
What does the caudate nucleus extend into?
The lateral ventricles
What projections are in the internal capsule?
Thalamocortical and corticothalamic projections
What is found in the genus of the corpus callosum?
The Corticobulbar tracts for movements of the face
Where in the brain are the corticobulbar tracts for movement of the face found?
The genu of the corpus callosum
What is in the posterior limb of the internal capsule?
The corticospinal tracts from the upper and lower part of the body
Where in the internal capsule are the corticospinal tracts for the upper and lower part of the body?
The Posterior Limb of the internal capsule
What is included in the Lentiform nucleus?
The Putamen and the internal and external Globus Pallidus
What is the substantia nigra a part of?
The basal ganglia
What is included in the striatum?
The caudate nucleus and the putamen
What are the caudate nucleus and the putamen collectively known as?
The Striatum
What are the four principal nucleus of the basal ganglia?
- Striatum (caudate + putamen)
- Globus pallidus internal and external)
- Substantia nigra (reticulata + compacta)
- Subthalamic nucleus
What are the parts of the substantia nigra?
Substantia Nigra Reticulata
Substantia Nigra Compacta
What are the parts of the Globus Pallidus?
- Globus Pallidus external
- Globus Pallidus internal
What can the basal ganglia principal nuclei be divided into?
- Input
- Output
- Intrinsic nuclei
What is the Input nucleus?
The Striatum (Caudate + Putamen)
What information does the Striatum receive?
Receives information from the cortex on the body’s position (sensory) and the motor plan from the supplementary/premotor motor cortex
Where in the basal ganglia is information from the cortex on the body’s position and the motor plan sent to?
The striatum (caudate + putamen)
What are the Output Nuclei?
Globus Pallidus and Substantia Nigra Pars Reticulata
What do the output nuclei of the Basal ganglia do?
Send out information from the basal ganglia to the supplementary motor cortex/premotor cortex to initiate or stop movements