Lecture 7 - Motor Systems

Question 1

What is the role of the Primary Motor Cortex in regards to cortical drive movement?

Answer 1

• Controls execution of movement

- ex: pick up iced coffee

Question 2

What is the role of the Supplementary Motor Area in regards to cortical drive movement?

Answer 2

• Coordination and execution of sequences of movement, attainment of motor skills
• aides in coordination and execution of that movement; gets a lot of info from cerebellum and basal ganglia

Question 3

What is the role of the Premotor Area in regards to cortical drive movement?

Answer 3

• Coordinates selection of appropriate motor plans for voluntary movements
• knows what movements to do based on prior experiences
• ex: In order to reach I flex my shoulder, extend my elbow, I open and close my fist

Question 4

Where is the internal capsule and what is its structural significance?

Answer 4

• Medially bordered by thalamus and caudate
• Laterally bordered by globus pallidus and putamen
• major highway system between our brain and extremities

Question 5

What borders the internal capsule?

Answer 5

• Medially bordered by thalamus and caudate

- Laterally bordered by globus pallidus and putamen

Question 6

How is the internal capsule somatotopically organized?

Answer 6

• medial is upper body and lateral is lower body

Question 7

What somatotopic organization do we see with the corticospinal pathways through the brainstem (specially, midbrain) and spinal cord?

Answer 7

• dorsal and lateral is for lower body and as you move more medial and ventral it is for upper body

Question 8

Where do we see a split of the two major tracts of the corticospinal pathway? Whats the general % split between how many fibers go into each tract?

Answer 8

• cervicomedullary junction
• 85% will decussate and turn into lateral corticospinal tract
• 15% remain ipsilateral to become anterior corticospinal tract

Question 9

Define a myotome. What information does it provide?

Answer 9

• Group of muscles innervated by a single spinal nerve
• group muscles based off their spinal nerve root which allows us to look at movements and determine what part of spinal nerves are damaged

Question 10

Where are the different corticospinal tracts located in the white matter of the spinal cord?

Answer 10

• medial tracts - around anterior column of white matter

- lateral tracts - lateral and dorsal aspects of white matter

Question 11

How does the neuromuscular function differ from other chemical synapses?

Answer 11

• Highly specialized synapse between a motor neuron and its target muscle fiber
• Essential for muscle contraction & prevention of muscle atrophy
• motor end plate has deep folds to increase surface area

Question 12

Define the specific structures involved in the neuromuscular junction synapse.

Answer 12

• synaptic boutons - terminal axons of motor neuron
• motor end-plate - area under synaptic boutons w/ junctional folds
• NMJ synapse - where AcH is released and binds to allow AP to travel through

Question 13

How is a motor unit defined? What are the different types of motor units that were reviewed?

Answer 13

• alpha motor neuron + muscle fibers
• Type 1a - slow MU for sustained muscle contractions
• Type 2a - fast fatigue-resistant MU for slow, large force production
• Type 2b - fast fatigable for brief, but forceful contractions (fight or flight)

Question 14

What is the functional relevance of the Size Principle?

Answer 14

• As input increasers, progressively larger motor units are activated that leads to larger forces generated
• used to conserve energy