Basal Ganglia Pathways

Direct Pathway = Disinhibition of the ThalamusMotor Cortex excites the Striatum (cauduate nucleus and putamen)Leads to inhibitory signals to the Globus pallidus internal Also leads to inhibitory signals to the Substantia Nigra pars reticulata/reticularisIn the mean time, Substantia Nigra pars compacta = dopaminergic signalling to Striatum via D1 receptorsFurther enhances Inhibitory signal of Striatum and Pars reticulataVA/VL nuclei of Thalamus = excited = talks back to cortexUltimately resulting in Muscle movement

Indirect Pathway = Dampening down signal (less movement = fine-tuning to prevent overstimulation probably)Motor Cortex excites the Striatum (cauduate nucleus and putamen)Leads to inhibitory signals to the Globus pallidus externalLeads to disinhibition of Subthalamic nucleiSubthalamic Nucleus = excites Pars reticulata and globus pallidus internal Leads to inhibition of Thalamus = lowers output = less movementIn the mean time, Pars compacta = dopamine signalling via D2 receptors to enhance inhibition of globus pallidus externa