Motor Systems

Question 1

What is the function of the Primary Motor Cortex

Answer 1

Controls execution of movement

Question 2

What is the function of the supplementary motor area

Answer 2

Coordination and execution of sequences of movement, attainment of motor skills

Receives info from cerebellum and basal ganglia

Question 3

What is the function of the premotor area

Answer 3

Coordinates selection of appropriate motor plans for voluntary movements

Help execute motor function

“Picks motor plan from experiences or motor memory”

Question 4

What are 2 systems in descending motor tracts?

Answer 4

Lateral and Medial Motor Systems

Question 5

What are the tracts in the lateral Motor Systems

Answer 5

Lateral Corticospinal Tract

Rubrospinal Tract

Question 6

What are the tracts in the Medial Motor Systems

Answer 6

Anterior Corticospinal Tract
Reticulospinal Tract
Tectospinal Tract
Vestibulospinal Tract

Question 7

What does the Lateral Corticospinal Tract control

Answer 7

Controls movements of extremities

-particularly important for rapid, dexterous movements at individual digits or joints

Question 8

What is unique about the internal capsule

Answer 8

Somatotopically organized

Question 9

What does the Anterior Corticospinal Tract control?

Answer 9

Controls bilateral axial and girdle muscles

Question 10

What does the Rubrospinal Tract control?

Answer 10

Controls movements fo the extremities

• modulation of flexor muscle tone
• inhibition of anti-gravity muscles (extensors)
• modulation of reflex activity (flexor withdrawal reflex)

Question 11

What does the reticulospinal tract control

Answer 11

Automatic posture and gait related movements

• pontine: inhibit limb flexors and excite extensors
• medullary: excite limb flexors and inhibit extensors

Question 12

What does the tectospinal tract control

Answer 12

Controls coordination of head and eye movements

-effect: head movement to match eye movements

Question 13

What are the 3 major plexi that we can find peripheral nerves?

Answer 13

Cervical Plexus C3-C5
- Diaphragm innervation

Brachial Plexus (C5-T1)
-UE innervation

Lumbosacral Plexus (L1-S4)
-LE innervation

Question 14

What is a myotome

Answer 14

Group of muscles innervated by a single spinal nerve

Question 15

What is a neuromuscular junction and why are they important

Answer 15

Highly specialized synapse between a motor neuron and its target muscle fiber

Important because it is essential for muscle contraction and prevention of muscle atrophy

Question 16

How many NMJ for each muscle fiber

Answer 16

1

Question 17

What are the synaptic boutons

Answer 17

Terminal axons of motor neuron

Question 18

What is the motor end plate in a NMJ

Answer 18

• Area that falls under synaptic boutons
• junctions folds
  - AcH ligand gated synaptic boutons

Question 19

Explain the NMJ synapse

Answer 19

AP form presynaptic motor neuron triggers release of ACh into synaptic cleft

AcH binds to ACh receptors, which open to allow Na to flow into muscle fiber — > leads ESPS —> AP travels down muscle fiber to facilitate contractions —> Acetylcholinesterase breaks down Ah to end contraction

Question 20

Describe Type Ia (type, location and function)

Answer 20

Slow Motor Unit

Smaller muscles
Sustained muscle contractions

Question 21

Describe Type IIa (type, location and function)

Answer 21

Fast fatigue - resistant Motor Units

Intermediate in size
Generate 2x force as slow, and better resistant to fatigue than FF

Question 22

Describe Type IIb (type, location and function)

Answer 22

Large muscles

Brief, but forceful contractions

Question 23

What is the size principle in regards to the Motor Unit

Answer 23

Regulation of muscle force

Weak synaptic stimulation recruits smallest motor units

As inputs increases, progressively larger motor units are activated —> larger forces generated

Question 24

What is the order of the muscle fiber recruitment

Answer 24

Slow —> Fast Fatigue- resistant —> Fast Fatigable