Motor Systems I

Question 1

What deficit is characterized by poverty of voluntary movements, weakness, changed reflexes (usually increased) – Upper Motor Neuron Syndrome?

Answer 1

Deficit in motor cortex

Question 2

What deficit is characterized by lack of smooth, coordinated movements?

Answer 2

Deficit in cerebellum

Question 3

What deficit is characterized by hyperkinetic and hypokinetic disorders, involuntary/spontaneous movements without solicitation

Answer 3

Deficit in basal ganglia

Question 4

Located just anterior to central sulcus, Betz cells (largest pyramidal cells that are unique to PMC and function as output generators). Area 4.

Answer 4

Primary motor cortex

Question 5

What is Area 6?

Answer 5

Premotor cortex and supplementary motor area

Question 6

What is Area 8?

Answer 6

Frontal eye fields (voluntary eye movement)

Question 7

What two criteria need to be met to be classified as motor cortical?

Answer 7

1. Agranular (i.e. it has poorly developed granular and sensory layers [II and IV] and well developed pyramidal layers [III and V])
2. Must be able to induce movement with low intensity stimuli.

Question 8

Where do some of the efferent projections from the primary motor cortex go to?

Answer 8

Basal Ganglia – corticostriate tract
Red Nucleus – corticorubral tract
Pontine nuclei – corticopontine tract (huge! en route to cerebellum)
Reticular Formation – corticoreticular tract
Spinal Cord – corticospinal tract (terminates in contralateral dorsal horn, intermediate gray and ventral horn)
Cranial Nerve Nuclei – corticobulbar tract

Question 9

What PMC projections does CN V get?

Answer 9

Mostly contralateral, but some bilateral

Question 10

What PMC projections does CN VII get?

Answer 10

PMC projects bilaterally to the upper portion of the facial nucleus which innervates the upper face and projects to the contralateral lower portion of the facial nucleus which innervates the lower face.

Question 11

What PMC projections does CN IX & X get?

Answer 11

Mostly contralateral but some bilateral

Question 12

What PMC projections does CN XI get?

Answer 12

Ipsilateral

Question 13

What PMC projections does CN XII get?

Answer 13

Mostly contralateral, but some bilateral

Question 14

Where does the corticospinal tract cross and synapse?

Answer 14

Crosses in the pyramids (pyramidal decussation) & synapses in spinal cord.

• Alpha motor neurons for motor output
• Dorsal horn for modulation of sensory inflow
• Intermediate gray for reflex pathway and spinal integration

Question 15

How do cortical cells increase and decrease force of contraction?

Answer 15

INCREASE firing RATE to INCREASE force of contraction. DECREASE firing RATE to DECREASE force of contraction.

Question 16

What is the path of the corticospinal tract?

Answer 16

Starts at pre central gyrus, travels down through the pons and into the medulla where it decussates at the pyramidal decussation into the cervical spinal cord, resulting in contralateral innervation. Ultimately, the tract terminates in the ventral horn (where all of the alpha motor nears are), but also goes to the intermediate gray (reflex systems) and dorsal horn (sensory info).

*Important for integrating sensory info with motor, not just exerting motor control