BASAL GANGLIA 1
BASAL GANGLIA AND
ITS MOTOR FUNCTIONS
MBCHBII, B.PHARMII, BSP II
11/7/2017 DR.AGABA D. COLLINS
Objectives
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1-Structure and Nuclei of Basal Ganglia
2-Connections of Basal Ganglia
3-Functions of Basal Ganglia
4-Disorders of Basal ganglia
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Basal ganglia
4 Is subcortical mass of grey matter found in the
cerebral hemisphere
It’s a unique area of the brain (high MR and
demand for O2)
Accessory motor system, like cerebellum
Basal ganglia receive most of their input signals
from the cerebral cortex itself and also return
almost all their output signals back to the cortex
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Anatomical relations to other brain structures
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Nuclei of basal ganglia
6 On each side of brain, each ganglia has;
Caudate nucleus, putamen, Globus pallidus,
substantia nigra and sub thalamic nucleus.
Located mainly lateral to and surrounding the
thalamus,
Occupy a large portion of the interior regions of
both cerebral hemispheres.
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Neuronal circuitry to basal ganglia
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BASAL
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Two most important circuits
1) Putamen circuit
2) Caudate circuit
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The putamen circuit
Controls complex patterns of motor activity e.g.
learned skills
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writing letters of alphabet, Cutting papers with scissors, hammering nails,
shooting a basketball through a hoop, passing a football, throwing a
baseball, most aspects of vocalization, controlled movements of the eyes,
and virtually any other of our skilled movements, most of them performed
subconsciously.
Putamen circuit has input from parts of brain
adjacent to primary motor cortex
Outputs do go mainly back to the primary motor
cortex or closely associate premotor and
supplementary cortex
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Abnormalities of putamen circuit
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The way putamen circuit execute patterns of
movement is poorly known.
However, when a portion of the circuit is
damaged or blocked, certain patterns of
movement become severely abnormal
These include;-
Lesions of the substantia nigra lead to the
common and extremely severe disease of rigidity,
akinesia, and tremors (Parkinson’s disease)
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lesions in the Globus pallidus frequently lead to
spontaneous and often continuous writhing
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movements of a hand, an arm, the neck, or the
face (athetosis)
A lesion in the subthalamus often leads to sudden
flailing movements of an entire limb
(hemiballismus)
Multiple small lesions in the putamen lead to
flicking movements in the hands, face, and other
parts of the body, called chorea
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The caudate circuit
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plays a major role in this cognitive control of motor activity
caudate nucleus receives large amounts of its input from the
association areas of the cerebral cortex overlying the
caudate nucleus
Signals return back to the prefrontal, premotor, and
supplementary motor areas of the cerebral cortex, but with
almost none of the returning signals passing directly to the
primary motor cortex.
Role appreciated on seeing a lion-the responses that follow
(1) turning away from the lion, (2) beginning to run, and (3)
even attempting to climb a tree. All these are coordinated
through caudate circuit.
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Specific neurotransmitters in BG system
Dopamine pathways from the substantia nigra to
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1)
the caudate nucleusand putamen
2) GABA pathways from the caudate nucleus and
putamen to the globus pallidus and substantia nigra
3) Acetylcholine; pathways from the cortex to the
caudate nucleus and putamen
4) Multiple general pathways from the brain stem that
secrete norepinephrine,serotonin and enkephalin
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Clinical syndromes from BG damage
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1) Athetosis
2) Hemiballismus
3) Parkinson's disease
4) Huntington’s chorea
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Parkinson's disease
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Also called paralysis agitans
Results from widespread destruction of
that portion of substantia nigra (the pars
compacta) that sends dopamine-
secreting nerve fibers to the caudate
nucleus and putamen
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Parkinson's disease
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Features
1) rigidity of much of body musculature
2) involuntary tremor of the involved areas
even when the person is resting at a fixed
rate of 3 to 6 cycles per second
3) serious difficulty in initiating movement
(akinesia)
Cause of the abnormal motor effects is
unknown
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Parkinson's disease (treatment)
21 Administration of the drug L-dopa to patients
(dopamine itself wont work)
Administration of the drug L- deprenyl. This
drug inhibits monoamine oxidase
Treatment with Transplanted Fetal Dopamine
Cells
Treatment by Destroying Part of the Feedback
Circuitry in the Basal Ganglia.
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Huntington’s chorea
22 Hereditary disorder
Usually begins causing symptoms at age 30
to 40 years
At first, flicking movements occur in
individual muscles and then progressive
severe distortional movts of the entire body
Severe dementia develops along with the
motor dysfunctions
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Huntington’s chorea (causes)
23 Abnormal movts of Huntington’s disease are due
to;
1) Loss of most of the cell bodies of the GABA-
secreting neurons in the caudate nucleus and
putamen
2) Loss of acetylcholine-secreting neurons in many
parts of the brain
Dementia results from loss of Ach-secreting neurons
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Assignment
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Function of the basal ganglia to change the timing
and to scale the intensity of movements.
Agnosia
Personal neglect syndrome.
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References
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Guyton and Hall (2006): Textbook of Medical
Physiology. 11th Edition
Sembulingam (2012): Essentials of Medical
Physiology. 6th Edition
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