Extra Pyramidal Motor Systems

Question 1

What is the function of the pyramidal motor system?

Answer 1

Important for planning and initiating voluntary motor movement and muscle ton

Question 2

What is the function of the extrapyramidal motor system?

Answer 2

Important for motor programming, habitual behaviors, and plays a small role in cognition and emotion

Question 3

What is the function of the cerebellum?

Answer 3

Important for balance, equilibrium, and real time motor adjustment

Question 4

What are the four functional loops of the extrapyramidal motor system?

Answer 4

Movement loop

Oculomotor loop

Prefrontal loop

Limbic loop

Question 5

What are the the three major inputs (afferents) to the striatum?

Answer 5

Cortico-striatal pathway

Nigro-striatal pathway

Thalamo-striatal pathway

Question 6

What is the cortical striatal pathway?

Answer 6

Projections arise from the cortex and project to the neostriatum via the internal capsule

These projections are excitatory (glutamatergic)

Question 7

What is the nigro-striatal pathway?

Answer 7

Projections from the substantia nigra pars compacta (SNc) to the neostriatum are modulatroy dopaminergic neurons

Question 8

What is the thalamo-striatal pathway?

Answer 8

Projections from the thalamus tot he neostriatum are excitatory (glutamatergic)

Question 9

What are the two major efferent inputs?

Answer 9

Globus pallidus (GPi) and project to the thalamus

Neostriatum projects to the substantia nigra pars reticularis (SNr)

Both are inhibitory/GABAergic

Question 10

Describe the substantia nigra’s role in information integration

Answer 10

Integrates information from the nuclei of the indirect descending corticospinal pathway

Information moves reciprocally between these nuclei and the SN

Means the SN can influence movement via the thalamus or via these alternative nuclei that project directly to the spinal cord

Question 11

What are the two paths that the GPi sends projections to the thalamus through?

Answer 11

Ansa lenticularis or lenticular loop - passes under the internal capsule to the thalamus

Lenticular fasciculus - passes through the internal capsule to the thalamus

Question 12

Describe the Direct pathway

Answer 12

Projects directly from the striatum to the GPi or SNr

Facilitates movement by reducing inhibition of thalamic activity

When dopamine is released in this pathway it acts on D1 receptors and is excitatory

Question 13

Describe the indirect pathway

Answer 13

Projects from the striatum to the GPe then to the subthalamic nucleus, then to the GPi or SNr

Inhibits movement by increasing inhibitory action on the thalamus

Dopaminein this pathway acts on D2 receptors and is inhibitory

Question 14

What degenerates in Parkinson’s disease?

Answer 14

Dopaminergic neurons that project from the SNc to neostriatum (nigrostriatal pathway)

Leads to reduced excitation of the direct pathway and reduced inhibitory drive from the indirect pathway

Question 15

What are the motor symptoms of parkinson’s disease?

Answer 15

Resting tremor

Cogwheel rigidity

Bradykinesia

Postural instability

Speech and swallowing disturbances

Question 16

What is essential tremor?

Answer 16

Rhythmic oscillating movements that can be fast or slow

typically affects upper extremities, head, tongue, lips, and vocal cords

Question 17

What is resting tremor?

Answer 17

Occurs when limbs are relaxed and decreases in intensity or disappears with movement

Question 18

What is intention tremor?

Answer 18

Produced with purposeful movement toward a target

Question 19

What is the difference between UMN lesions and basal ganglia disorders?

Answer 19

UMN lesions - clasped-knife rigidity

Basal ganglia - cogwheel rigidity

Question 20

What are some treatment options for parkinson’s?

Answer 20

Carbidopa-levodopa (L-dopa)

Monoamine oxidase inhibitors (MAO) - slows breakdown of dopamine

Catechol-o-methylk transferase inhibitors (COMT) - slows breakdown of L-DOPA

Deep brain stimulation

Question 21

What is Wilson’s Disease?

Answer 21

Copper metabolism disease that causes progressive degeneration of the liver and basal ganglia

Appears much earlier in life than PD

Asymptomatic Kayser-Fleischer rings in the cornea

Question 22

What is Huntington’s disease?

Answer 22

Autosomal dominant progressive neurodegenerative disease

Striatum heavily impacted

Primary target is indirect pathway

Question 23

What are symptoms of Huntington’s disaese?

Answer 23

Choreiform movement

Tics

Athetosis

Dementia

Psychiatric disturbances

Question 24

What is ballismus?

Answer 24

Wild flinging movement of the extremities due to a basal ganglion lesion and commonly involves STN lesion - hyperkinetic affect

Question 25

What is hemiballismus?

Answer 25

Most common and characterized by unilateral (contra) flinging movements due to unilateral lesions of the STN