15 Basal Ganglia

Anatomy

Function

• direct for helpful movement

• indirect for unhelpful movement

• pars compacta/reticulata different parts of substantia nigra

• at rest: GP Internus and Pars Reticulata inhibits thalamus via GABA (tonic inhibition), no cortex stimulation

• action: direct/indirect pathway modulate thalamus

Direct Pathway

• cortex activate striatum via glutamate, which then inhibits pars reticulata and globus pallidus internus via GABA

• cortex also activates pars compacta that stimulates striatum via D1 dopamine to amplify the process

Indirect Pathway

• striatum stimulated and inhibit GP externus, thus disinhibit subthalamic nucleus that stimulates GP internus that inhibits thalamus

• cortex also stimulates pars compacta that inhibits striatum via D2

• D2 result: thalamus activated

Summary

Pars Compacta

• important because destroyed in parkinson's

Movement disorders

• hyperkinetic disorder: inhibition removed

• hypokinetic disorder: disinhibition not present