Motor Neuron Pathway

Front 1

Levels of control for motor output

Back 1

Spinal cord
Brain stem
Descending pathways

Front 2

Cerebrum

Back 2

-planning and initiation of movement

Front 3

Basal ganglia

Back 3

enforcement of desired movements and suppression of undesired movements

Front 4

cerebellum

Back 4

coordination and planning; timing and precision of fine movements; adjusting ongoing movements, motor learning of skilled tasks

Front 5

Brain stem

Back 5

Control of balance and posture, coordination of head, eye and neck movements

Front 6

Spinal cord

Back 6

Spontaneous reflexes, rhythmic movements, motor outflow to body

Front 7

Motor reflexes

Back 7

all reflexes involve a receptor structure and an associated afferent (sensory) neuron (primary afferent with cell body in sensory ganglion) and an efferent neuron (with its cell body in the CNS)

Front 8

Do all reflexes involve interneurons?

Back 8

Yes with the exception of the stretch reflex

Front 9

Central patterns generators

Back 9

Central pattern generator is a neural circuit capable of producing repetitive activity in the absence of any sensory input; it can be changed by sensory input

Front 10

Flexor-extensor rule

Back 10

motor neurons that innervate flexor muscles are located posterior to motor neurons that innervate extensor muscles

Front 11

Proximal-distal rule

Back 11

Motor neurons that innervate distal muscles are located lateral to motor neurons that innervate proximal muscles

Front 12

Organization of descending tracts

Back 12

-lateral descending tracts modify extremities and distal musculature

-medial descending tracts modify the trunk and proximal muscle

Front 13

Name the lateral pathways

Back 13

Lateral corticospinal tract
Rubrospinal tract

Front 14

Where does the lateral corticospinal tract originate?

Back 14

in the cortex - primary motor cortex

Front 15

Where do most of the fibers decussate in the lateral corticospinal tract?

Back 15

in the medulla and descend to contralateral motoroneurons

Front 16

What is the target of the lateral corticospinal tract?

Back 16

Lateral ventral horn - motor neurons and interneurons at all levels of the spinal cord

Front 17

Origin of the Rubrospinal tract?

Back 17

red nucleus in the midbrain

Front 18

Where does the rubrospinal tract decussate?

Back 18

immediately in the midbrain

Front 19

Target of rubrospinal tract

Back 19

lateral ventral horn

Front 20

Purpose of rubrospinal tract

Back 20

-minor in humans
-activation of flexor muscles and inhibition of extensor muscles
-play a role in movement velocity
-might be important pathway for recovery of some voluntary motor function after damage to corticospinal tract

Front 21

What is decorticate rigidity

Back 21

Abnormal flexion; lateral tracts are lesioned so only medial tracts are open

Front 22

What is decerebrate rigidity

Back 22

extension posturing; lateral tracts are lesioned so only medial tracts are open

Front 23

Medial tracts

Back 23

-favor extensor tone
-close proximity to medial ventral horn
-control proximal and girdle musculature involved in posture, balance

Front 24

Is medial ipsilateral or contralateral?

Back 24

ipsilateral or bilateral

Front 25

Lower motor neuron syndrome

Back 25

-flaccid weakness
-decreased or absent muscle tone
-decreased tendon reflexes
-muscle twitches
-atrophy
-decreased/absent resistance to passive range of motion

Front 26

Upper motor neuron syndrome

Back 26

-spastic weakness
-hypertonia
-hyperreflexia
-velocity-dependent resistance to passive ROM
-Babinski's sing abnormal

Front 27

Spinal shock

Back 27

-loss of descending control
-flaccid paralysis below lesion
-less of tendon reflexes
-will resolve