Basic FunctionStriatum – Caudate and Putamen - receives input from motor cortical areas and substantia nigra pars compacta (SNpc)Pallidum - GPi and Gpe - relays output information to the ipsilateral thalamusThalamus – VA and VL nuclei - relays excititory response to motor cortexSubthalamic Nucleus - relays excitatory ouput to GPiSubstantia Nigra (pc) – dopaminergic excitation/inhibition to striatum (pr) – output to thalamus along w/ GPi
GPi Anatomy Thalamic Fasciculus 1. Ansa Lenticularis - From GPi loops under post limb to VA/VL of thalamus 2. Lenticular Fasciculus - From GPi pass through internal capsule on top of STN to VA/VL of thalamus1. 2.
Basal Ganglia Disclosure Statement1. The caudate, putamen, and globus pallidus act on the motor thalamus, which acts on the motor cortex2. There are no descending spinal cord tracts w/in the basal ganglia3. All circuitry is ipsilateral and projects to the same side of the brain4. Basal Ganglia circuits affect movements of the contralateral side
Neurotransmitters1. Glutamate - excitatory2. GABA - inhibitory3. Dopamine a. D1 - Excitatory b. D2 - Inhibitory4. ACh
Cortical Direct Pathway Glutmate GABA Inhibit the InhibitorThe Direct pathway turns UPthe motor thalamus, and inturn the motor cortex. Thusit TURNS UP motor activity!
Cortical Indirect Pathway Glutmate GABA Inhibit the Inhibitor InhibitedThe Indirect pathway turnsDOWN the motor thalamus, andin turn the motor cortex. Thus itTURNS DOWN motor activity!
Dopaminergic EffectDopamine EXCITES thedirect pathway, andINHIBITS the indirect D1 - excitatorypathway! D2 - inhibitoryThe overall concept ofdopamine is to increaseexcitatory output
ACh EffectsThe overall concept ofACh is to TURN DOWNmotor activity! StriatalACh INHIBITS direct and InterneuronsEXCITES indirect pathways!
Pathologic Lesions to Basal Ganglia1. Hypokinetic - lesion of the direct pathway - ex. Parkinson’s2. Hyperkinetic - lesion of the indirect pathway - ex. Hemiballismus, Huntingtons Chorea