Basal Ganglia PDF

Basal ganglia 11 November 2024 09:54 Function; - Motor control - Motor learning and control of movement - Cognition and emotion Structures; If you count all distinct structures mentioned, there are 10 major components of the basal ganglia: 1. Caudate nucleus...

Basal ganglia 11 November 2024 09:54 Function; - Motor control - Motor learning and control of movement - Cognition and emotion Structures; If you count all distinct structures mentioned, there are 10 major components of the basal ganglia: 1. Caudate nucleus Neurosci Page 1  1. Caudate nucleus 2. Putamen 3. Nucleus accumbens 4. Globus pallidus externus (GPe) 5. Globus pallidus internus (GPi) 6. Subthalamic nucleus (STN) 7. Substantia nigra pars compacta (SNc) 8. Substantia nigra pars reticulata (SNr) 9. Olfactory tubercle 10. (Optional) Limbic extensions of the basal ganglia, such as certain parts of the amygdala, may also be considered in broader contexts. Caudate nucleus Putamen and globus pallidus Neurosci Page 2 Inputs of basal ganglia Cerebral cortex (majority) Thalamus and substantia niagra pars compacts Input zone Main outputs Gpi Thalamus Frontal cortex (motor) Substantia nigra pars reticulata Neurons in superior collicilus (midbrain)- head and eye movement Neurosci Page 3  Neurons in superior collicilus (midbrain)- head and eye movement Pathways of basal ganglia Direct- facilitates the initiation of purposeful movement Indirect- inhibits unwanted movement Direct; Cerebral cortex Glutamate release striatum Glutamate release GABA thalamus GABA GPi movement Reduced inhibition of thalamus by Gpi due to incoming GABA from striatum Dopamine modulation Dopaminergic neurones in substantia nigra pars compacts modulate direct and indirect pathways The neurons in the striatum possess 2 types of dopamine receptors - D1 and D2 D1 involved with direct pathway - excitation of neurones in striatum D2 involved with indirect pathway - inhibition of neurones in striatum Dopamine has the same outcome on both systems, it increases activity of d1 (throtrle) while decreasing activity of d2(brakes) - promoting movement Dopamine's effect on direct pathway Substantia nigra pars compacta D1 Neurosci Page 4  Indirect pathway inhibits unwanted movement Effectiveloy inhibiting thalamus glutamate Cerebral cortex Thalamus GABA glutamate GPi striatum glutamate STN GABA GPe movement GABA Dopamine's effect on the indirect pathway Effectiveloy inhibiting thalamus glutamate Cerebral cortex Thalamus GABA glutamate GPi striatum glutamate STN GABA GPe movement GABA D2 Neurosci Page 5  striatum glutamate STN GABA GPe movement GABA D2 SNpc Reverses pathway by reducing inhibitory effect of striatum Neurosci Page 6 Parkinson's disease Idiopathic (unknown cause) Hypokinetic movement disorder Degeneration of nigrostriatal dopaminergic neurons of substantia nigra Neurosci Page 7 Signs and symptoms Bradykinesia (slowness of movement) Akinesia (difficulty initiating movement) Opposite to cerebellar lesion Resting tremor Rigidity Postural disturbance Short stooped steps Reduced arm swing Blank facial expression Slurred voice Difficulty stopping movement Non-motor; Impairment of cognitive and behavioural functions Psychological and emotional changes' Treatments Precursor of dopamine (levodopa) as dopamine cannot cross blood brain barrier Huntington's disease Hyperkinetic movement disorder Autosomal dominant disease Selective loss of medium spiny neurons in the striatum that project to GPe (indirect pathway) Neurosci Page 8 Putamen and cordate nucleus atrophy, causing large lateral ventricals Signs and symptoms; Chorea - dance Exhibits involutary movement - quick jerky Neurosci Page 9 Both diseases impare cognitive and emotional function Neurosci Page 10