2.4 Flashcards
Parkinson’s disease symptoms
Basal nuclei:
- Bradykinesia
- Tremor at rest
- Rigidity
- Reduction of the initiation of movement
- Loss of dopamine
Indirect pathway is a movement inhibitor. PD is an agonist of this pathway.
What is the basal nuclei?
A collection of nuclei that work together to plan and initiate movement.
What makes up the basal nuclei?
Caudate nucleus
Putamen
Globus pallidis (pallidum)
Subthalamic nucleus
Substantia nigra
Integration of movement
Basal nuclei
Cerebellum
Cerebral cortex
Thalamus
The basal nuclei and the cerebellum both influence the cerebral cortex through the thalamus.
- The thalamus has an excitatory effect on the cerebral cortex.
- The baseline effect of the basal nuclei on the thalamus is inhibitory which inhibits the cerebral cortex.
3 categories of basal nuclei
Input: receive input to the basal nuclei
- blue
Intrinsic: function remains within the basal nuclei
- yellow
Output: send signals to other structures
- green
Input to the basal nuclei
These nuclei receive input from other structures
- Caudate nucleus and putamen (together called the striatum)
Intrinsic
These nuclei receive input from other basal nuclei and send output to other basal nuclei
- globus pallidus (lateral part)
- subthalamic nucleus
- part of the substantia nigra
Output
These nuclei send output primarily to the thalamus.
- globus pallidus (medial part)
- substantia nigra
Output is inhibitory
Motor loop
Plan sequence of movements
Information flows from:
- motor cortex
- caudate nucleus and putamen
- globus pallidus and substantia nigra
- thalamus
- back to supplementary motor cortex
Input is also contributed by the somatosensory cortex.
Oculomotor loop
Voluntary saccadic eye movements
Information flows from:
- frontal eye field
- caudate nucleus
- globus pallidus and substantia nigra
- thalamus
- back to frontal eye field
Input is contributed by the prefrontal cortex and the posterior parietal cortex.
Association loop
Planning complex movement
Information flows from:
- prefrontal cortex
- caudate nucleus
- globus pallidus and substantia nigra
- thalamus
- back to prefrontal cortex
Input is contributed by the premotor and posterior parietal cortex
Limbic loop
Emotion and motivation of movement
Information flows from:
- anterior cingulate gyrus and orbitofrotal cortex
- striatum
- ventral pallidum, globus pallidus, and substantia nigra
- thalamus
- back to anterior cingulate gyrus and orbitofrontal cortex
Input is contributed by the medial and lateral temporal lobe and other limbic areas (hippocampus, amygdala, and entorhinal area)
Striatum
Caudate nucleus and putamen (principle input nuclei)
- input from cortex and thalamus is excitatory
- input from other basal nuclei is inhibitory
Output is inhibitory and goes to globus pallidus and substantia nigra.
Globus pallidus (lateral) and subthalamic nuclei
Intrinsic nuclei
Principle input is from the striatum to the globus pallidus is inhibitory.
Globus pallidus also receives excitatory input from subthalamic nucleus.
Direct pathway of basal nuclei//motor cortex
End product: inhibition is lifted leading to thalamic excitation of motor cortex.
Allows deliberate, purposeful movement.
Indirect pathway of basal nuclei//motor cortex
End product: inhibition is enhanced leading to thalamic inhibition of motor cortex
Inhibits excessive, purposeless movements.
Excitatory neurotransmitters
Glutamate (GLU)
Acetylcholine
Dopamine (DA)
Inhibitory neurotransmitters
GABA
Dopamine
Which neurotransmitter is both inhibitory and excitatory?
dopamine
Neurotranmitters: Parkinson’s
Destruction of the dopaminergic cells of the substantia nigra.
Ultimately results in increased thalamic inhibition which means the cerebral cortex is understimulated.
Agonist to the indirect pathway.
Neurotransmitter: Huntington’s
Destruction of the GABAergic influence on the lateral globus pallidus.
Ultimately results in decreased thalamic inhibition which means the cerebral cortex is overstimulated.
Agonist to the direct pathway.
