Motor Systems Flashcards
Neurons give rise to corticospinal fibers located in the ____. Fibers also arise from premotor and supplementary motor cortices in ____.
M1 corticospinal neurons are organized as the ____.
Primary motor cortex (M1, area 4); area 6
Motor homunculus
CST fibers arising in the L motor cortex influence muscles on the R side. Fibers cross the midline in the ____.
CST lesions rostral to the decussation cause _____.
Lesions caudal to the desiccation cause ____.
Pyramidal decussation
Contralateral motor deficits
Ipsilateral deficits
The corticospinal fibers descend through the ____.
They pass through the corona radiata and converge to enter the ____.
Axons that terminate in the ____ are rostral in the capsule.
Axons that terminate at ____ are caudal in the capsule.
Internal capsule
Posterior limb of the internal capsule
Upper spinal arrangements
Lower levels
Corticospinal fibers originate from _____. Sensory info reaches ____ to provide feedback for the motor output.
Corticospinal neuron (UMN) descend from M1 to control _____ output.
They encode what?
M1; M1
LMN
Amount of force required to produce a movement and movement direction
The supplementary motor cortex consists of the medial portion of _____.
Fx?
Area 6
Organizing and planning the sequence/steps of muscle activation required to make a movement (M1 executes the movement)
Random finger movements elicit neural activity only in ____.
Same movements with multiple fingers elicits neural activity in ____ and _____.
Mentally rehearsing a specific sequence of finger movements without moving fingers elicits activity in _____.
Hand region of M1
Supplementary motor cortex and hand region of M1
Supplementary cortex but not M1
Premotor cortex contains _____.
Premotor cortex receives inputs from sensory areas of the parietal cortex and projects to ____.
Fx?
Area 6
M1, SC, RAS (reticular activating syndrome forming reticulospinal fibers that influence spinal motor neurons)
Preparation to move, organizes postural adjustments required to produce movement
Directs the control of the proximal limb muscles used to position the arm for movement tasks or to orient the body for movement
The basal nuclei are cell groups embedded in the ____. What three nuclei does it contain?
Fx?
Cerebral hemispheres
Subthalamic, substantia nigra, pedunculopontine tegmental nucleus
Fx in sets of parallel circuits: cerebral cortex -> basal nuclei -> thalamus -> cerebral cortex
Receive corticostriatal fibers from the cerebral cortex
The caudate and putamen are both _____.
Caudate location? What is the nucleus accumbens?
Putamen location?
Claustrum location?
Basal nuclei
Caudate: head forms a bulge in the lateral ventricle; at anterior level, the ventral/medial part of the striatum constitutes the nucleus accumbens.
Putamen: lateral to the internal capsule and globus pallidus; separated from globus pallidus by lateral medullary lamina
Lateral to putamen is white matter separated by external and extreme capsules; contains gray matter called the claustrum
Globus pallidus and sustantia nigra are both ___.
Globus pallidus lies medial to the ____, separated from it by the lateral medullary lamina. GP segments are separated by ___.
Substantia nigra is the most ventral part of the _____. It contains ____ and _____. What is the fx of each part?
Basal nuclei
Putamen; medial medullary lamina
Midbrain
Pars compacta: pigmented melanin neurons that synthesize dopamine; project to caudate nucleus and putamen
Pars reticulata: functional homologue of the medial segment of the GP
Basal nuclear activity are divided into ____ and ____ pathways.
Direct pathways facilitate what?
Indirect pathways inhibit what?
Effect?
Direct and indirect
Facilitate a flow of info through the thalamus
Inhibit this flow of info
Creates a balance in the inhibitory outflows of the basal nuclei; modulates the extent of this inhibition on target nuclei
What are the five basal nuclei tracts?
Pallidal fibers
Subthalamic fasciculus
Nigro-thalamic fibers
Nigro-striatal fibers
Striatonigral fibers
Pallidal fibers are ____ with high rates of spontaneous activity; they ____ their targets.
Pallidothalamic fibers target the ____ and ____ thalamic nuclei.
The subthalamic fasciculus is a reciprocal fiber tract between the ____ and _____. It contains ____ fibers.
GABAergic; inhibit
Ventral anterior and ventral lateral
Globus pallidus; subthalamic; excitatory
Nigro-thalamic fibers are non-dopaminergic fibers that originate in the ____ and terminate in the ____.
Nigro-striatal fibers are _____ fibers that originate in the ____ and terminate in the ____. These neurons get destroyed in _____.
Striatonigral fibers are _____ that originate in the _____ and terminate in the ______ in the ____. Loss of these fibers can cause ____.
Pars reticulata of the substantia nigra; VA and VL thalamic nuclei
Dopaminergic; pars compacta of the substantia nigra; caudate and putamen; Parkinson’s
GABAergic fibers (inhibitory); putamen; pars compacta of the substantia nigra; Huntington’s disease
Parkinson’s disease is caused from from loss of neurons in the ____.
S&S?
Treatment?
Substantia nigra
Tremors at rest, cogwheel rigidity (increase muscle tone), akinesia, bradykinesia, disturbances of eye movements, loss of postural reflexes
I-3,4-hydroxyphenylalanine (I-DOPA or levodopa): can cross the BBB and is converted to dopamine
Huntington disease cause what?
What are the symptoms?
Pt’s lose their ability to fx due to progressive involuntary movements and dementia
Absent mindedness, irritability, depression, clumsiness, and sudden falls
Choreiform movements increased until pt is bedridden
Cognitive fx and speech deteriorate -> severe dementia (caudate nucleus is lost)
Syndenham’s chorea is a ____ disease that affects children 5-15.
What is the cause?
What are the symptoms?
Autoimmune
Major manifestation of rheumatic fever (infection with group A beta-hemolytic streptococci): results from antibodies against strep react with epitopes in the basal nuclei
Rapid, irregular, aimless movements of the limbs, face, trunk; muscle weakness, hypotonia
Ballismus is seen as ____.
What does it cause?
Caused by?
Hemiballismus
Uncontrolled flinging movements of limbs
Vascular lesions localized to contralateral subthalamic nucleus or subthalamic fasciculus
Chorea is what?
What disease is this seen in?
Caused by?
Rapid irregular involuntary dance-like movements that flow from one body region to another
Huntington’s, tar dive dyskinesia, side effect of Parkinson’s treatment
Loss of neurons in the indirect pathway
Athetosis is what?
Brisk athetosis?
Intense athetosis?
Continuous writhing of distal portions of extremities, more obvious in UE
More brisk and resemble chorea= choreoathetosis
More intense, sustained, and resemble dystonia= athetotic dystonia
Corticonuclear fibers are organized in parallel with the _____.
What are direct fibers?
Indirect fibers?
They contain UMN that influence what?
CST
Fibers that project to cranial motor neurons
Fibers that project to midbrain and pontine reticular formations adjacent to CN nuclei
Motor nuclei of CN V, VII, XII Nucleus ambiguus (CN IX, X) Accessory nucleus (CN X)
UMN lesions of fibers targeting the facial nucleus cause what?
LMN lesions of the root of CN VII cause what?
Central facial paralysis (supranuclear facial palsy): drooping of the muscles at the corners of the mouth and lower face of the contralateral side
Bell (facial) palsy: flaccid paralysis of facial muscles of upper and lower portions of the face on the ipsilateral side
UMN lesions in fibers targeting the nucleus ambiguus cause what?
UMN lesions in fibers targeting the hypoglossal nucleus cause what?
Deviation of palate/uvula to the side ipsilateral to the lesion
Tongue protrusion to the side contralateral to the lesion
*both are due to the pull of the opposite muscle
