Norden - Extrapyramidal Motor System Flashcards
Involved in motor “programs” (arm swing when you walk), habitual behaviors, and in the modulation of movement
Extrapyramidal system
Involved in balance, equilibrium, posture, tone; the proper timing and coordination of learned, skilled motor movement and the correction of movement errors during on-going movement
Cerebellum
Neither the _ nor the _ project to the spinal cord, rather they have connections which influence firing of UMN’s in the corticospinal tract
Extrapyramidal system
Cerebellum
The major output division of the globus pallidus
GPi (glous pallidus internal portion)
Central players of the extrapyramidal system
Caudate and putamen
Hypo-kinetic disorders of the extrapyramidal motor system
Parkinson’s disease
Parkinsonism
Hyper-kinetic disorders of the extrapyramidal motor system
Huntington’s Chorea
Ballismus
Dystonia
• A family of disorders involving an abnormal posturing of the trunk or
extremity, caused by a sustained contraction and hypertrophy of muscles
involved
• Can be generalized or focal; most common focal are torticollis and
blepharospasm
• Etiology unknown; lentiform nucleus abnormalities have been found
• Can be primary (idiopathic) or secondary (called symptomatic)
Dystonia
Hyperkinetic extrapyramidal disorder • Due to lesions of the subthalamic nucleus • Results in violent, uncontrollable movements (contralateral to lesion) • Can be a fatal disorder
Ballismus
• ETIOLOGY: Autosomal dominant disorder with genetic anticipation linked
to an abnormal expansion in the length of a CAG triplet repeat sequence;
chromosome 4; hyperkinetic extrapyramidal disorder
• PATHOLOGY: A neurodegenerative disorder characterized by loss of the
medium-spiny neurons that are involved in the indirect pathway; overall
effect is to decrease inhibition of the thalamus (VA, VL) and thus
abnormally excite UMNs in cortex – leading to abnormal, uncontrollable
motor movements
• Also involves loss of other cortical neurons (prefontal cortex,
hippocampus)
• Results in chorea, mental changes
Huntington’s Chorea
this is the system that plans and initiates a voluntary motor movement (direct corticospinal) and maintains background tone in muscle that allows the movement to be made (indirect corticospinal
Pyramidal motor system
Plays a primary role in the execution of motor “programs”, habitual learning, and in the modulation of movement
Extrapyramidal motor system
Monitoring of on-going movement, proper timing and coordination of learned, skilled motor movement and the correction of movement errors during on-going movement
Cerebellum
Medium spiny neurons are prominent where ?
Neostriatum (caudate and putamen)
Medium spiny neurons are prominent in the neostriatum (caudate and putamen) and use ____ as a neurotransmitter
GABA
What are the excitatory neurons of the neostriatum ?
Aspiny neurons, excitatory, use acetylcholine
The pars compacta’s melanin containing neurons provide ______ input to the neostriatum
Domapinergic
The extrapyramidal motor system consists of ?
The neostriatum
Globus pallidus
Subthalamic nucleus
Substantia nigra
The 3 major afferent projections to the neostriatum are?
Cerebral cortex (cortico-striate)
Thalamus (thalamo-striate)
Substantia nigra (nigro-striate)
What Is the major neurotransmitter in cortico-striate and thalamo-striate projections?
Glutamate
Where do many of the cortico-striate axons come from?
A lot of them are collaterals from the cortico - spinal tract .
(This allows for the extrapyramidal system to “know” what movement is expected to be made)
What type of neurotransmitter does the pars compacta send to the striatum?
Dopamine.
Either + or -
What determines whether the dopamine that is used in the nigro-striate pathway is inhibitory or excitatory?
The type of postsynaptic dopamine receptor involved.
What are the major efferents out of the neostriatum ?
Globus pallidus and substantia nigra?
What neurotransmitter is used in efferent projections to the globus pallidus and substantia nigra out of the neostriatum ?
GABA
Where do the nuclei of the extrapyramidal motor system ultimately project to ?
The motor cortex .
NOT tHE SPINAL CORD
What thalamic nuclei does the neostriatum ( extrapyramidal motor system) project to ?
Ventral anterior nuclei (VA)
Ventral lateral nuclei (VL)
How does the extrapyramidal system modulate motor movement?
By providing feedback to the motor cortex that influences the firing of cortical UMN’s of the direct and indirect corticospinal tracts
At rest. Medium spiny neurons are ?
Quiescent
In the direct pathway, the dopaminergic projection from the substantia nigra to the neostriatum is ?
Exitatory
In the indirect pathway, there is ____ inhibition of the the thalamus.
(This is regarding the extrapyramidal motor system)
Increased
In the indirect pathway (extrapyramidal) the dopaminergic projection from the substantia nigra to the neostriatum is ?
Inhibitory
Disorder involving extrapyramidal motor system where the primary dysfunction is a decrease and slowing of movement
Hypokinetic disorders
Hypokinetic disorders include?
Parkinson’s disease
Parkinsonianism
What type of disease are huntington’s chorea, ballismus, and dystonia?
Hyperkinetic disorders
Extrapyramidal dz in which the major clinical manifestation is abnormal involuntary movement
Hyperkinetic disease
Parkinson’s Disease is caused by ?
Idiopathic, cause unknown. (90%) of cases
Parkinsonism -
Parkinson’s in which there is a known etiologic agent/cause.
Cause of parkinsons’ disease?
Loss of melanin-containing neurons of the pars compacta of the substantia nigra. 80-85%of substantia nigra must be lost to start seeing symptoms
What does the loss of melanin containing neurons of the substantia nigra do?
Loss of dopaminergic input to the neostriatum
This causes a decrease in the activity of the direct path (extrapyramidal motor loop) and and increase in the activity of the indirect pathway.
Dementia and then parkinsonism
Lewy body dementia
Parkinsonism then lewy body then dementia?
Parkinson, (50-80% of pts develop dementia)
Causes an increased incidence of both parkinsons and alzheimers
Occurs second to swine flu.
Lethargy, due to the reticular formation’s involvement
Encephalitis lethargica
Where can strokes occur that could cause the development of Parkinson’s disease?
Branches of the ACA, PCA, and anterior choroidal, which all supply the striatum.
Branches of the posterior cerebral artery which supply the substantia nigra
What can happen with people who have long, chronic exposure to low levels of CO or who attempt suicide by CO poisoning?
Increased incidence of parkinson’s disease
What are some known insults that can cause parkinson’s disease?
Encephalitis lethargica (2nd to swine flu)
Stroke of branches of PCA, ACA, MCA, and ant choroidal
CO exposure
Herbicides and pesticides
Toxic manifestation of some prescription drugs
Long term Meth use.
Why is drooling a symptom of parkinson’s disease?
Swallowing is impaired
What gene is errant in Huntington’s chorea?
Gene 4.
Has expansion in the length of a CAG triplet repeat sequence
A neurodegenerative disease characterized by the loss of medium spiny neurons in the caudate and putamen. These normally project to the GPe in the indirect pathway.
Overall effect of loss of neurons is decrease in inhibitory output to the thalamus. Results in abnormal activation of UMN’s
Huntington’s chorea
motor disturbance characterized by non-rhythmic continuous involuntary
movements, particularly of the distal extremities, face and tongue a. In advanced stages, the patient is never at rest; the patient has no control; it can involve
all parts of the body, can be unilateral or bilateral
Chorea
early in the disorder, the patient characteristically tries to hide the
movements (tries to work them into normal movements)
a. As the disease progresses, there is severe mental deterioration and usually marked
paranoia
Mental changes associated with huntington’s disease
What neurological disease has the highest patient suicide rate, at about 10%?
Huntington’s chorea
Occurs with lesions of the subthalamic nucleus; lesions effectively remove excitatory input
to GPi thereby decreasing the inhibitory outflow of extrapyramidal motor system nuclei; this leads to an abnormal activation of UMNs (resulting in violent movements)
Ballismus
Most common form of focal dystonia.
Involves cervical neck muscles
Torticollis
Focal dystonia; orbicularis oculi
Blepharospasm
Focal dystonia involving vocal apparatus
Spasmodic dysphonia
Focal dystonia involving upper extremity only when writing
Writer’s cramp
Where are lesions in ballismus?
Subthalamic nucleus
Where is problem of huntingtons disease
Medium spiny neurons in caudate and putamen that project to GPe degenerate
Where is degeneration in Parkinson’s disease?
Substantia nigra
Dystonia can be caused by lesions in the?
Lentiform nucleus
