BASAL GANGLIA Flashcards
GENERAL FEATURES
Function of the basal ganglia
initiate
+
gross control
skeletal muscle movements
GENERAL FEATURES
Major components
(4)
Striatum - telencephalon
(caudate nucleus and putamen)
Globus Pallidus - telencephalon
(external and internal segments)
Substantia nigra - midbrain
Subthalamic nucleus - diencephalon
GENERAL FEATURES
Basal Ganglia Pathways
(components)
cerebral cortex
+
ventrolateral nucleus of the thalamus
+
basal ganglia
GENERAL FEATURES
Basal Ganglia Pathways
(circuits)
Direct and Indirect basal ganglia pathways
GENERAL FEATURES
Basal Ganglia Pathways
(similarities about both pathways)
receive extensive inputs from cortex + project back to the motor cortex (by VL nucleus) + “disinhibition” process
BASAL GANGLIA PATHWAYS
Describe the direct pathway
Excitatory input from cortex → striatum inhibitory GABA neurons (caudate nucleus and putamen) → outflow to inhibitory GABA neurons globus pallidus (internal segment) → project to thalamus (VL) “disinhibited” → thalamic input excites the motor cortex → promotion of movement
BASAL GANGLIA PATHWAYS
Describe the indirect pathway
Excitatory input from cortex → striatal inhibitory GABA neurons (caudate nucleus and putamen) → project to globus pallidus (external segment) → external segment inhibitory GABA neurons project to subthalamic nucleus → subthalamic nuclues is disinhibited → subthalamic nucleus neurons excites internal segment (globus pallidus) → internal segment inhibitory GABA neurons inhibit the VL nucleus (thalamus) → decreased cortical excitation → supression of unwanted movement
BASAL GANGLIA PATHWAYS
Dopamine effects
dopaminergic neurons in the substantia nigra project to the striatum
+
increase the direct pathway (through D1)
inhibit the indirect pathway (through D2)
+
increase cortical stimulation
BASAL GANGLIA PATHWAYS
Cholinergic effects
Cholinergic neurons in striatum
+
increase the indirect pathway
+
less cortical stimulation
CLINICAL CORRELATE
Lesions of the basal ganglia
movement disorders (dyskinesias)
+
tremor (involuntary)
+
altering the balance between the indirect and the direct pathways
(affecting both)
CLINICAL CORRELATE
Lesions of the direct pathway
underactive cortex + hypokinetic disturbances
(slowing or absence of spontaneous movements)
Parkinson disease
CLINICAL CORRELATE
Lesions of the indirect pathway
chorea
(Huntington and Sydenham)
+
athetosis
(Huntington and others diseases)
+
dystonia
(often occurs with athetosis)
+
tics
CLINICAL CORRELATE
Parkinson disease
CLINICAL CORRELATE
Huntington disease
CLINICAL CORRELATE
Wilson disease
CLINICAL CORRELATE
Hemiballism
Wild, flinging movements of limbs
CLINICAL CORRELATE
Tourette Syndrome
OBS
OCD = obsessive-compulsive disorder
ADHD = attention deficit hyperactivity disorder
TREATMENT
antipsychotic agents
