Structures involved in involuntary movements are shown on models, in animations, and on gross coronal and axial sections. Diagrams show the cortex-to-cortex loop and the nigrostriatal pathway. The direct and indirect pathways are shown. The direct pathway facilitates movement while the indirect pathway inhibits movement on the opposite side of the body. Clinical videos of two diseases, Parkinson's and Huntington's, are examples of interruption of the balance between excitation and inhibition in these pathways.
