Org. of Motor Systems

Question 1

contrast lower motor neurons and upper motor neurons

Answer 1

• LMN
  
  • motor neurons that communicate directly between the CNS and somatic muscle
• UMN
  
  • neurons originating in the brain that communicate closely with LMNs
  • many undergo decussation allowing them to exert bilateral or contralateral control

Question 2

name the parts of the spinal cord cross section

Answer 2

• 1 = DCML
• 2 = dorsal horn, sensory neurons
• 3 = ventral horn, LMNs
• 4 = UMNs

Question 3

name the starts of the motor pathways

Answer 3

Question 4

the medial pathway is biased for _____

and

the lateral pathway is biased for ______

Answer 4

the medial pathway is biased for extension

and

the lateral pathway is biased for flexion

Question 5

Answer 5

Question 6

Answer 6

Question 7

describe the location of lower motor neurons in relation to function

Answer 7

• in the ventral horn of the spinal cord, flexor and adductor neurons lie dorsal to the extensor and abductor neurons
• cells for distal muscles lie laterally to those for truncal muscles (i.e.proximal muscles)

Question 8

describe amyotrophic lateral sclerosis (ALS)

Answer 8

• progressive degenerative disease of the motor system
  
  • amyotrophy = atrophy of muscle
  • lateral sclerosis = hardening of the lateral columns of the spinal cord
• degeneration of anterior horn cells and motor CN V, VII, X, XII parts of pyramidal tract and primary area
• often begins with involvement of lower limbs followed by upper limbs

Question 9

describe the bulbar manifestations of the ALS

Answer 9

• bulbar manifestations
  
  • reduction of cough reflexes -> risk of aspiration pneumonia
  • involvement of bulbar motor nuclei -> difficulty in swallowing, coughing and speaking

Question 10

describe clinical features seen in ant. spinal artery syndrome

Answer 10

• paraparesis
• bilateral extensor plantar response
• bilateral loss of pain and temp. below lesion
• touch, vibration, proprioception intact
• sexual functions impaired