FUNCTIONS OF BASAL GANGLIA
PLANNING & PROGRAMMING –> Discharge starts even before commencement of movement.
EXECUTION OF MOTOR TIMING, INTENSITY & SEQUENCES –> Basal Ganglia gets input from cortex projects back to cortex (Prefrontal, premotor, Supplementary motor area). These Corticospinal & Corticobulbar neurons influence Proximal & Distal limb.
MUSCLE TONE –> Inhibits tone, decreases stretch reflex (BG LESION – HYPERTONIA).
COGNITIVE FUNCTION –> Connects to Prefrontal & Orbitofrontal Cortex.
SPEECH –> Lesion in Lt head of Caudate Nucleus – causes DYSARTHRIA
In lower animals, higher centre for MOTOR ACTIVITY.
DISEASES OF BASAL GANGLIA
PARKINSONISM / PARKINSON’S DISEASE/PARALYSIS AGITANS/ SHAKING PALSY
Named after James Parkinson (English Physician) -1817.
Has both HYPOKINETIC & HYPERKINETIC features.
Loss of PARS COMPACTA neurons of Substantia Niagra that leads to loss of DOPAMINE in NIGROSTRIATAL Pathway.
Imbalance between Excitation & Inhibition
- LEVODOPA/L-DOPA –>Dopamine cannot enter Blood Brain Barrier but L-Dopa can cross. So, L-Dopa is given as replacement of Dopamine.
- BROMOCRIPTINE –> Synthetic Dopamine Agonist. Can cross BBB.
- ANTICHOLINERGIC – BENZHEXOL — >Inhibits Cholinergic System.
- LEVODOPA + CARBIDOPA –>Carbidopa inhibits conversion of L-Dopa to Dopamine outside BBB, minimizes side effects and prolongs the action of L-Dopa.
- L-DEPRYNYL –>Slows the progression of disease. Inhibits MAO, prolongs Dopamine action.
- Surgical treatment –>
- Implantation of dopamine secreting tissue (adrenal medulla, foetal striatal tissue)
- Surgical lesion :
- VA, VL Nuclei
- Globus Pallidus
- Use of pacemaker
Difference between Cerebellum and Basal Ganglia
|No input from spinal cord||Direct input from spinal cord|
|Input from all areas of cerebral cortex||Input only from Motor areas.|
|Output is more widespread, reaches prefrontal & all premotor areas.||Restricted to premotor & primary motor cortex.|
|Few connections with brainstem.||Has rich connections with brainstem.|
|Usually causes HYPERTONIA (Rigidity)||Causes HYPOTONIA|
|Tremors at rest. Disappears with activity.||Intentional tremor. Disappears with rest & reappears with exercise/movt.|
|Lesion affects opposite side||Affects same side|
‘All change is not growth, as all movement is not forward.’