Motor Systems: Control of Locomotion

Question 1

descending control of locomotion

Answer 1

association cortex/thalamus/limbic system
–> basal nuclei –> extrapyramidal systems –> spinal cord

Question 2

what structure provides choice of action and decision making

Answer 2

basal nuclei

Question 3

what structure directs final motor execution

Answer 3

command centers (extrapyramidal systems)

Question 4

reciprocal innervation

Answer 4

activation of one muscle group influences the activity of another muscle group

Question 5

stance phase execution

Answer 5

facilitate extensors

• pontine reticulospinal tract
• vestibulospinal tract

Question 6

swing phase execution

Answer 6

protraction: facilitates flexors
retraction: facilitates extensors

• medullary reticulospinal tract
• rubrospinal tract

Question 7

central pattern generators

Answer 7

group of spinal interneurons that synapse onto LMNs to coordinate rhythmic output

Question 8

what is cross talk between CPG interneurons

Answer 8

coordination between CPG interneurons across the same spinal cord segment AND between different spinal cord segments

Question 9

what are 2 mechanisms that help maintain posture

Answer 9

direct: tonic excitation of LMNs for extensors via UMN pathways

indirect: modulation of stretch reflex circuits via gamma LMN pathways

Question 10

anticipatory maintenance

Answer 10

contraction of antagonistic muscles that occurs prior to contraction of the intended muscle

Question 11

signs of C1-C6 lesions

Answer 11

thoracic: UMN signs
pelvic: UMN signs

Question 12

signs of C6-T2 lesions

Answer 12

thoracic: LMN signs
pelvic: UMN signs

Question 13

signs of T3-L4 lesions

Answer 13

thoracic: normal
pelvic: UMN signs

Question 14

signs of L4-S1 lesions

Answer 14

thoracic: normal
pelvic: LMN signs

Question 15

signs of cortical lesions - pyramidal tracts

Answer 15

loss of skilled/precise voluntary movement

NORMAL gait

Question 16

signs of brainstem/spinal cord lesions - extrapyramidal tracts

Answer 16

loss of voluntary movement caudal to lesion
hyperreflexia
spasticity

Question 17

spinal walking

Answer 17

central pattern generators take over control of voluntary movement if spinal cord injury does not resolve in chronic cases of loss of voluntary movement (> 3 months)

does not always occur

Question 18

what do CPGs require to initiate first rhythmic movement

Answer 18

sensory information on feet

does NOT get processed by cerebrum

Question 19

schiff-sherrington posture

Answer 19

T3-L3 myelopathy resulting in loss of central pattern generators

• marked extensor tone in thoracic limbs
• flaccid hind limbs
• opisthotonus
• normal voluntary movement in thoracic limbs when supported in pelvic limbs