Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Alien hand syndrome wikipedia , lookup
Transcranial Doppler wikipedia , lookup
Limbic system wikipedia , lookup
Neurodegeneration wikipedia , lookup
Hypothalamus wikipedia , lookup
Neuropharmacology wikipedia , lookup
Cortical stimulation mapping wikipedia , lookup
Hemiparesis wikipedia , lookup
Auditory system wikipedia , lookup
Basal ganglia Chapter 56 Dr. Z Akbari Motor Control by the Basal Ganglia The BG are the five interactive structures on each side of the brain: Caudate nucleus nucleus, putamen, putamen globus pallidus, pallidus and amygdal. amygdal Associated nuclei: VA & VL nuclei l i off thalamus, h l Subthalamic nucleus of the diencephalon, Substantia nigra of the midbrain. The main function: Influence the motor cortex via pathways through the thalamus. The role: Aid in planning and execution of smooth movements. Change the timing and scale the intensity of movement . BG also contribute to affective and cognitive functions.Dr. Z Akbari Organization of the basal ganglia 1- Caudate nucleus Striatum: major recipient of input from cortex, 2- Putamen 2 BS, thalamus. 3- Globus pallidus (Int, Ext) Major output projection…VA &VL of thalamus 4- Substantia nigra g …..to Sup Colliculus….eye movement 5 Subthalamic 5S bth l i nucleus l With the exception of the primary visual and auditory cortices, most regions of the cerebral cortex project topographically to the striatum. Dr. Z Akbari The basal ganglia in relation to surrounding structures Dr. Z Akbari Neural circuitry of the basal ganglia cerebral cortex ……. Striatum,…….. GPi,……… GPi ,……… thalamus,……back to the cortex. The output from GPi to the thalamus is inhibitory, whereas the output from the thalamus to the cerebral cortex is excitatory. Dr. Z Akbari Direct & indirect pathways through the b basal l ganglia li • Direct pathway (Excitatory) Cortex + Striatum GPi Thalamus • IIndirect di t pathway th (Inhibitory) Cortex + Striatum GPe STN + GPi Dr. Z Akbari Thalamus Dr. Z Akbari Some movement disorder result from imbalances in the direct & indirect pathways in the BG • Hypokinetic disorder Hyperkinetic disorder • Excessive motor activity • Impaired initiation of movement (akinesia akinesia)) Reduced amplitude & velocity of voluntary movement ( Bradykinesia Bradykinesia)) • Muscular rigidity( g y( resistance to passive displacement) • Tremor • Parkinson Dx Involuntary movement( dyskinesia) dyskinesia) muscle tone( hypotonia hypotonia)) Athetosis: slow, writhing movements of extremities Hemiballismus: violent largelargeamplitude movement of proximal limb( ballistic movement) Chorea: rapid & irregular writhing of limb and orofacial structures Dr. Z Akbari Huntington Parkinson disease The first example of a brain disorder from deficiency of a single neurotransmitter Dr. Z Akbari Parkinson Treatment: L - DOPA L – Deprenyl (MAOI) Surgical S i l iintervention t ti Dr. Z Akbari Dr. Z Akbari Lesions of subthalamic nucleus ……… ballism (involuntary, often violent, movements of the contralateral limbs ) Hemiballism result from disinhibition of the thalamus due to reduction in the tonic (and perhaps phasic) phasic) output from the GPi……… GPi……… permit thalamocortical neurons to respond in an exaggerated manner to cortical or other inputs inputs. OR Increase the tendency of these neurons to discharge spontaneously, leading t involuntary to i l t movements t Dr. Z Akbari Huntington’s disease Autosomal dominant Age of onset: 30 30--50 Abnormal gene on chromosome 4 Loss of intrastriatal GABA GABA--ergic and cholinergic neuron Symptom: Hyperkinetic choreiform movement , dementia Death 10 10--15 y years after onset of symptom y p Dr. Z Akbari Difference between the basal ganglia and cerebellar motor loop BG receive input from most areas of the cortex BG output from the BG is more widespread (Prefrontal & premotor areas) BG do not receive somatosensory information from ascending pathways in the SC & few connection with the brain stem nuclei Dr. Z Akbari Integration of motor control systems Spinal level Hindbrain level Cortical level Associated function of the cerebellum and Basal Ganglia Dr. Z Akbari The end Dr. Z Akbari