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- 1. BUI DEPARTMENT OFANATOMY ANA 304 NEUROANATOMY TOPIC: BASAL GANGLIA 1
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- 3. Basal ganglia • • The basalganglia/nuclei are collections of gray matter which are located at the base of each cerebral hemisphere. Are a group of subcortical structures found deep within the white matter of the brain. 3
- 4. Basal ganglia • • Form apart of the extrapyramidal motor system Work in synchrony with the pyramidal and limbic systems. 4
- 5. Basal ganglia -Components •Components and Relations 5
- 6. Basal ganglia -Components •Components and Relations 6
- 7. Basal ganglia – Components fivepairs of nuclei 7
- 8. • • • • • Five pairs ofnuclei Caudate nucleus ("tail") Putamen ("shell") (caudate nucleus + putamen = corpus striatum ("striped body")) Globus pallidus ("pale globe") Subthalamic nucleus Substantia nigra. Basal ganglia – Components 8
- 9. • • • Striatum, furtherconsists of the: Dorsal striatum, made by the caudate nucleus and putamen Ventral striatum, composed of nucleus accumbens and olfactory tubercle (forms part of the limbic system) • Globus pallidus, consists of an internal segment (GPi) and an external segment (GPe) • Subthalamic nucleus • Substantia nigra Basal ganglia – Components 9
- 10. Basal Ganglia -Components • • • • Caudate nucleus = caudate nucleus + putamen Lentiform nucleus: Putamen and Globus Pallidus Amygdala Claustrum 10
- 11. Classification of thebasal ganglia Traditional Classification • • • • Caudate nucleus Lentiform nucleus Amygdaloid body Claustrum Functional Classification • • • • Caudate nucleus Lentiform nucleus Subthalamus Substantia nigra 11
- 12. Functions of theBasal Ganglia • • Primary function = control and regulate activities of the motor and pre-motor cortical areas so that voluntary movements can be performed smoothly. Therefore concerned with motor refinement, acting as a tonically active break, preventing unwanted movements to start and also preventing excessive and exaggerated movements. 12
- 13. Functions of theBasal Ganglia cont’d • • • • • • • • • Voluntary movements - Initiation of movement Control of ramp movement Change from one pattern to another Programming and correcting movements while in progress (thalamocortical circuits) Postural control Righting reflex Automatic associated movements (walking) Control of muscle tone 13
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- 16. Corpus striatum • • • • Lies lateralto the thalamus Divided by a band of nerve fibers (internal capsule) into: Caudate Nucleus Lentiform nucleus. 16
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- 18. Caudate nucleus • • • • The caudatenucleus is C-shaped and presents Head, body, and tail The head is Large and lies in the frontal lobe. It is attached to the putamen of lentiform nucleus The body is tapering and curved into the tail The tail terminates in amygdaloid nucleus 18
- 19. Lentiform nucleus • • • • The lentiformnucleus is Wedge-shaped and lies: lateral to the Internal capsule. medial to the External capsule. Lateral to the external capsule is the claustrum and Extreme capsule 19
- 20. Lentiform nucleus • • Lentiform nucleusis comprised of Globus pallidus medially and Putamen laterally. The Globus pallidus is further divided into two: GP externus and GP internus 20
- 21. Amygdala and Claustrum • • • Amygdalalies close to the tail of the caudate nucleus, anterior to the hippocampus. It is more closely related to the limbic system The Claustrum function is not well known. Amygdaloid 21
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- 23. Substantia Nigra • • • • • • • • • • The substantianigra is present: In the midbrain Between the tegmentum and the basis pedunculi Mesencephalic in origin Highest concentration of GABA in CNS The substantia nigra consists of two components: Pars compacta : dorsal cell–rich portion Pigmented (neuromelanin) neurons = contain Dopamine Principal source of striatal dopamine Pars reticulata : ventral cell–sparse portion 23
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- 25. Connections of BG • • • • • Basalganglia RECEIVE INPUT through the Striatum which comprises of: Caudate nucleus Putamen Output leaves through the Globus pallidus 25
- 26. Connections of BG • • Thestriatum - considered to be the principal “input” structure of the BG since it receives the majority of afferents from the cerebrum and other parts of the brain. The Globus Pallidus + pars reticularis of the substantial nigra = the main “output” structures of the BG because they give off the main efferent fibre projections. 26
- 27. Connections of corpusstriatum • • • • Afferents Cerebral cortex- Corticostriate • Thalamic nuclei- Thalamostriate • Substantia nigra- Nigrostriate • Brainstem striatal fibres • • • • Efferents Globus pallidus- Striatopallidal Substantia nigra- Striatonigral 27
- 28. Afferent: Cerebral cortex- Corticostriate • Thalamicnuclei- Thalamostriate • Substantia nigra- Nigrostriate • Brainstem striatal fibres Efferent: Globus pallidus- Striatopallidal Substantia nigra- Striatonigral 28
- 29. Connections of globuspallidus • • • • • • GP has 2 segments –a medial & lateral segments also known as GP interna and GP externus GP internus & substantial nigra pars reticularis = output Receive afferent – striatum, subthalamic nucleus – Efferents GP externa– subthalamic N GP interna – thalamus – motor areas 29
- 30. Connections that controlMotor Activities • • • • • The BG influence the motor activities by means of two Pathways: Direct pathway Indirect pathway Direct pathway turns up motor activity Indirect pathway turns down motor activity 30
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- 33. The Role ofSubstantial Nigra 33
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- 35. Summary of thepathways • • • • • • • • • • Direct pathway Involves GP internus. Stimulatory to movement. Dopamine stimulates direct pathway ACH inhibits direct pathway Indirect pathway It involves GP externus and subthalamus in addition to structures of direct pathway. Is inhibitory to movement Dopamine inhibits indirect pathway ACH stimulates Indirect pathway 35
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- 37. BLOOD Supply toBG • • • • The arterial supply - mainly from the middle cerebral artery, a continuation of the internal carotid artery. The main artery is named lenticulostriate artery and, as the name implies: provides most of the circulation to the striatum and the lenticular nucleus. 37
- 38. Basal Ganglia -Blood Supply cont’d • • There is also a small amount of supply from the anterior cerebral artery and the anterior choroidal artery, both of which are also branches of the internal carotid artery, supplying the more anterior aspect of the ganglia, (i.e. the head of the caudate nucleus). The particularly large artery(from ACA) is referred to as medial striate artery (of Heubner) = Recurrent artery of Heubner 38
- 39. Blood Supply toBG cont’d • • The substantia nigra and the subthalamic nucleus are more posterior and thus receive their vasculature from branches of the posterior cerebral and posterior communicating arteries. The venous drainage is via striate branches of the internal cerebral vein, which drain into the great cerebral vein. 39
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- 41. Diseases of basalganglia • • Change in muscle tone Abnormal involuntary movement 41
- 42. Parkinsonism • • • • • • • Degeneration ofdopamine- producing cells in substantia nigra- depletion of dopamine in striatum Resting tremor Rigidity – simultaneous contraction of flexors and extensors Bradykinesia = Slowness of movement Hypokinesia No paralysis, sensory loss, ataxia •Less activation of direct pathway and less inhibition of indirect pathway May be associated with heroine addiction and antipsychotic drugs 42
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- 44. Huntington’s disease – • • Hereditarydisease of unwanted movements. It results from degeneration of the caudate and putamen, and produces continuous dance-like movements of the face and limbs - choreoathetosis 44
- 45. Hemiballism - • • Hemiballism isthe flailing movements of one arm and leg (one-sided), which is caused by damage (i.e., stroke) of the subthalamic nucleus. Discrete lesions of the subthalamic nucleus in humans lead to hemiballism, a syndrome characterized by violent, forceful choreiform movements that occur on the side contralateral to the lesion and involve primarily proximal muscles. 45
- 46. SUMMARY • • • When the substantianigra is not working properly, input to the basal ganglia is not modulated properly, and the globus pallidus receive progressively less information. Without this information, the initiation of movement (i.e. , timing) message is less effective and the person’s movements progressively become slower (i.e., bradykinesia). Parkinson’s disease is related to a deterioration of the substantia nigra and globus pallidus, and is characterized by resting tremors and bradykinesia. 46
- 47. Thank You. Wishing you successin all your Exams. 47