Motor Systems

Question 1

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 ____.

Answer 1

Primary motor cortex (M1, area 4); area 6

Motor homunculus

Question 2

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 ____.

Answer 2

Pyramidal decussation

Contralateral motor deficits

Ipsilateral deficits

Question 3

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.

Answer 3

Internal capsule

Posterior limb of the internal capsule

Upper spinal arrangements

Lower levels

Question 4

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?

Answer 4

M1; M1

LMN

Amount of force required to produce a movement and movement direction

Question 5

The supplementary motor cortex consists of the medial portion of _____.

Fx?

Answer 5

Area 6

Organizing and planning the sequence/steps of muscle activation required to make a movement (M1 executes the movement)

Question 6

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 _____.

Answer 6

Hand region of M1

Supplementary motor cortex and hand region of M1

Supplementary cortex but not M1

Question 7

Premotor cortex contains _____.

Premotor cortex receives inputs from sensory areas of the parietal cortex and projects to ____.

Fx?

Answer 7

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

Question 8

The basal nuclei are cell groups embedded in the ____. What three nuclei does it contain?

Fx?

Answer 8

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

Question 9

The caudate and putamen are both _____.

Caudate location? What is the nucleus accumbens?

Putamen location?

Claustrum location?

Answer 9

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

Question 10

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?

Answer 10

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

Question 11

Basal nuclear activity are divided into ____ and ____ pathways.

Direct pathways facilitate what?

Indirect pathways inhibit what?

Effect?

Answer 11

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

Question 12

What are the five basal nuclei tracts?

Answer 12

Pallidal fibers

Subthalamic fasciculus

Nigro-thalamic fibers

Nigro-striatal fibers

Striatonigral fibers

Question 13

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.

Answer 13

GABAergic; inhibit

Ventral anterior and ventral lateral

Globus pallidus; subthalamic; excitatory

Question 14

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 ____.

Answer 14

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

Question 15

Parkinson’s disease is caused from from loss of neurons in the ____.

S&S?

Treatment?

Answer 15

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

Question 16

Huntington disease cause what?

What are the symptoms?

Answer 16

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)

Question 17

Syndenham’s chorea is a ____ disease that affects children 5-15.

What is the cause?

What are the symptoms?

Answer 17

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

Question 18

Ballismus is seen as ____.

What does it cause?

Caused by?

Answer 18

Hemiballismus

Uncontrolled flinging movements of limbs

Vascular lesions localized to contralateral subthalamic nucleus or subthalamic fasciculus

Question 19

Chorea is what?

What disease is this seen in?

Caused by?

Answer 19

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

Question 20

Athetosis is what?

Brisk athetosis?

Intense athetosis?

Answer 20

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

Question 21

Corticonuclear fibers are organized in parallel with the _____.

What are direct fibers?

Indirect fibers?

They contain UMN that influence what?

Answer 21

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)

Question 22

UMN lesions of fibers targeting the facial nucleus cause what?

LMN lesions of the root of CN VII cause what?

Answer 22

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

Question 23

UMN lesions in fibers targeting the nucleus ambiguus cause what?

UMN lesions in fibers targeting the hypoglossal nucleus cause what?

Answer 23

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