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Cns 10
1. The basal ganglia are a group of subcortical nuclei that integrate motor, cognitive, and limbic functions through loops with the cerebral cortex and thalamus. 2. The basal ganglia receive input from the entire cerebral cortex and influence muscle movement through outputs to the thalamus and motor cortex. 3. Disorders of the basal ganglia can result in hyperkinetic or hypokinetic movement disorders like Parkinson's disease, which involves reduced dopamine in circuits regulating voluntary movement.
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Cns 10
- 1. Voluntary Movement Mostcomplex Cerebral cortex integration Initiated at without external stimuli Can become involuntary Riding a bicycle
- 2. Rhythmic Movement Combinationof reflex and voluntary Initiated and terminated by input from cerebral cortex After initiation becomes reflexive Maintained by spinal interneurons Example: Running
- 3. CNS Integration 3levels of control Spinal cord Brain stem and cerebellum Cerebral cortex and basal nuclei Thalamus relay station Simple movements Spinal reflexes Postural reflexes Both can have cerebellar input
- 4. Integration of VoluntaryMovement Coordination between: Cerebral cortex Cerebellum Basal ganglia 3 steps: Decision making and planning Initiating movement Executing movement Feedforward postural reflexes Adjustment in anticipation of changes
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- 7. Anticipates body movementReflexive adjustment to balance change Prepares body for threat: blink, duck, "tuck & roll" Combines with feedback Feed Forward: Postural Reflex Feedforward reflexes and feedback of information during movement
- 8. Overview Anatomy Loops& Pathways Motor Disorders 1 1 1 1
- 9. Basal Nuclei Inthe cerebral white matter of each hemisphere are a groups of subcortical nuclei called the basal nuclei The main mass of this tissue include the caudate nucleus, putamen, globus pallidus (paleostriatum), subthalamic nucleus and substantia nigra
- 10. Basal Nuclei Theputamen and globus pallidus together form a mass called the lentiform nucleus. The comma shaped caudate nucleus arches superiorly over the diencephalon. The lentiform nucleus flanks the internal capsule laterally Collectively the caudate nucleus and the lentiform nuclei are called the corpus striatum because the fibers of the internal capsule that course past these nuclei give them a striped appearance
- 11. Basal Nuclei Thebasal nuclei are functionally associated with the subthalamic nuclei (located in the floor of the diencephalon) and the substantia nigra(pars compacta and para reticulata) of the midbrain The amygdaloid nucleus sits on the tail of the caudate nucleus, functionally it belongs to the limbic system
- 12. Basal Nuclei Functionally,the basal nuclei can be viewed as complex neural calculators that cooperate with the cerebral cortex in controlling movement
- 13. Basal Nuclei Thebasal nuclei receive inputs from the entire cerebral cortex as well as from other subcortical nuclei Via relays through the thalamus, the basal nuclei project to the premotor and prefrontal cortices
- 14. Basal Nuclei Viarelays the basal nuclei influence muscle movements directed by the primary motor cortex The basal nuclei has no direct access to the motor pathways The precise role of the basal nuclei is difficult to determine since their function overlaps to some extent with the cerebellum The basal nuclei are particularly important in starting, stopping, and monitoring movements executed by the by the cortex
- 15. Components of theBasal Ganglia Input Nuclei Corpus Striatum (aka Striatum) Caudate Putamen Output Nuclei Globus Pallidus Interna Substantia Nigra Pars Reticulata* Intermediate Nuclei Globus Pallidus Externa Subthalamic Nucleus* Substantia Nigra Pars Compacta*
- 16. Basal Ganglia Non-MotorLoops Executive/Prefrontal Loop Limbic Loop Oculomotor Loop Motor Loop (Focus of our journey) Regulation of upper motor neurons Necessary for normal initiation
- 17. Pathways of MotorLoop Direct Pathway Overall Excitatory Indirect Pathway Overall Inhibitory
- 18. Direct Pathway (akathe Express Route) CORTEX PUTAMEN (GPe) (STN) GP interna VA/VL THALAMUS Glutamate (+) Glutamate (+) GABA (-) GABA (-)
- 19. Indirect Pathway (aka, scenic route) CORTEX PUTAMEN GP externa STN GP interna VA/VL THALAMUS Glutamate (+) GABA (-) Glutamate (+) GABA (-) GABA (-) Glutamate (+)
- 20. What is missing?Effect of DA on pathways Direct Pathway: Stimulates Indirect Pathway: Inhibits Overall Excitatory
- 21. DA in DirectPathway Substantia Nigra pars compacta Dopamine (+)
- 22. DA in theIndirect Pathway Dopamine (-) Substantia Nigra pars compacta
- 23. Direct and IndirectMotor Loops CORTEX PUTAMEN (GPe) (STN) GP interna VA/VL THALAMUS Glutamate (+) Glu(+) GABA (-) GABA (-) (--) CORTEX PUTAMEN GP externa STN GP interna VA/VL THALAMUS Glutamate (+) GABA (-) GABA (-) GABA (-) Glutamate (+) DA (+) Glu(+)
- 24. Striatal Connexions Cerebralcortex Caudate nucleus Putamen Globus pallidus Substantia nigra Tone inhibitor dopamine Thalamus (corticostriate) – motor region (thalamostriate) (Nigrostriate) Striatonigral Inhib GABA striatopallida Subthalamic nucleus Subthalamic fasciculus - - + Pallidonigral 1 2 2 2 3
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- 26. Command for movement- + + Motor Cortex Basal Ganglia Cerebellum Thalamus
- 27. Movement Cortical control– “ What is to be done” Basal ganglia and cerebellum – “ How it is to be done” Disease to the extrapyramidal system gives rise to extrapyramidal disorders ( basal ganglia, substantia nigra and subthalamic nucleus )
- 28. Dopamine A Monoamineneurotransmitter Formed by an amino acid (tyrosine) which is modified by tyrosine hydroxylase to form DOPA . DOPA decarboxylase removes CO2 from DOPA and forms Dopamine which is a precurser to norepinephrine and epinephrine .
- 29. Dopamine Systems 4main systems Mesolimbic Tubero-infundibular Incertohypothalamic Nigrostriate
- 30. Dopamine systems Mesolimbic: cell origin are in the ventral tegmentum of the midbrain which sends axons to the limbic system. Excessive dopamine result in psychotic episodes ex. Schizophrenia. Tubero – infundibular : Dopamine release in this system inhibits release of pituitary prolactin and influences oxytocin and vasopressin secretion Incertohypothalamic: Dopamine release in this system influences endocrine secretion
- 31. Dopamine systems Nigrostriate: Dopamine neurons in the substantia nigra send axons to the caudate nucleus and the putamen as tone inhibitors.
- 32. How do Ikeep this all straight? Basal Ganglia (Caudate, Putamen, and GP) Medium Spiny neurons = GABAergic GABA = Inhibitory Cortex, Thalamus, STN Here, looking at Glutamatergic neurons Glut=excitatory Dopamine from Substantia Nigra pc Acts on Putamen
- 33. Functions 1.Involved in planning and programming of movements. 2.The nuclei are involved in monitoring muscle movements that are relatively slow and sustained or patterned. 3. Inhibits the muscle tone 4. Regulates the subconscious gross movements. 5. Caudate nucleus – role in cognitive process
- 34. Movement Disorders HyperkineticHemiballismus Huntington’s Disease Hypokinetic Parkinson’s Disease Drug Induced (Neuroleptics)
- 35. Hemiballismus CORTEX PUTAMENGP externa STN GP interna VA/VL THALAMUS Glutamate (+) GABA (-) GABA (-) GABA (-) Glutamate (+) Glutamate (+) +
- 36. Hemiballismus Injury usuallyto STN Decreased inhibition (Indirect Pathway) Characterized by uncontrolled flinging TX: Dopamine Antagonist
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- 38. Huntington’s Disease CORTEXPUTAMEN GP externa STN GP interna VA/VL THALAMUS Glutamate (+) GABA (-) Glutamate (+) GABA (-) GABA (-) Glutamate (+) +
- 39. Parkinson’s Disease Lossof DA neurons in substantia nigra Four cardinal symptoms Bradykinesia, Akinesia, Rigidity, Tremor
- 40. Parkinson’s Disease CORTEXPUTAMEN (GPe) (STN) GP interna VA/VL THALAMUS Glutamate (+) Glu(+) GABA (-) GABA (-) (--) CORTEX PUTAMEN GP externa STN GP interna VA/VL THALAMUS Glutamate (+) GABA (-) GABA (-) GABA (-) Glutamate (+) DA (+) Glu(+)
- 41. Dopamine Clinical symptoms:Occur when 70 %– 80% of Dopamine depleted Decreased Dopamine formation Reduced dopaminergic Impulses to the striatum Enhanced excitation of globus palledus and subthalamic nucleus Increased inhibition of the thalamus Decreased cortical regulation
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- 43. In Terms ofEtiology and Clinical Picture, Major Symptoms Involve: Bradykinesia - Slowness in Initiation and Execution of Voluntary Movements Rigidity –it can be lead pipe or cog wheel. Increase Muscle Tone and Increase Resistance to Movement (Arms and Legs Stiff) Tremor - Usually Tremor at Rest, When Person Sits, Arm Shakes, Tremor Stops When Person Attempts to Grab Something Postural Instability - abnormal fixation of posture (stoop when standing), equilibrium, and righting reflex Gait Disturbance - Shuffling Feet
- 44. Usually Other AccompaniedAutonomic Deficits Seen Later in Disease Process: Orthostatic Hypotension Dementia Dystonia Ophthalmoplegia Affective Disorders
- 45. Chorea and athetosis Chorea: caudate nucleus damage Rapid , irregular involuntary movements of short duration. Athetosis: Lenticular nucleus Continuous , slow twisting movement.
- 46. Pyr system (CStract) 1. Weakness 2. Spasticity 3. Inc tone 4. No atrophy 5. Babinski UMN lesion 1. Weakness 2. Dec DTR 3. Dec tone 4. Atrophy 5. Downgoing toes LMN lesion EPS (Basal Ganglia) Chorea (Huntington’s, Syndenham’s) Athetosis (choreoathetosis in HD) Hemiballismus (stroke) Parkinson’s disease (resting tremor, bradykinesia, truncal instability, dementia) Cerebellum Intention tremor Ataxia (fall towards lesion, gait & trunk dystaxia, dysrhythmokinesia, dysdiadochokinesia, dysmetria) Nystagmus Dec DTR/tone ipsilaterally Asthenia (muscle tire easily )
Editor's Notes
- #17 Executive loop: involves dorsolateral prefrontal cortex and part of the caudate Limbic loop: involves cingulate cortex and nucleus accumbens Oculomotor loop: involves cadate and superior colliculus (responsible for eliciting rapid eye movements called saccades) Focus here on the motor loop, (the other loops are similar so if we learn this now it should help demystify the others) BG influences movement by regulating upper motor neurons-necessary for normal initiation of voluntary movement Responds in anticipation of and during movements
- #18 Balance between the two are not well-defined, but they work together for movement. While they are presented separately here, keep in mind they are working simultaneously.
- #19 Overall Excitatory by disinhibiting the upper motor neurons in the cortex (promotes movement)
- #20 Overall inhibitory. Serves to modulate the disinihibitory actions of the direct pathway
- #21 DA stimulates the direct pathway and inhibits the indirect pathway for an overall excitatory effect. DA input is needed for stimulation of the putamen, along with input from the cortex.
- #22 Predominantly D1-receptors
- #23 Predominantly D2-Receptors
- #36 Lesion in STN reduced inhibitory outflow of basal ganglia in indirect pathway Sx: violent, involuntary movement of limbs