Descending Motor Systems

Question 1

Function of descending motor systems

Answer 1

Control motor neurons
Autonomic function
Modifying sensory transmission
Control motor neuron excitability (gamma loop)

Question 2

2 major classifications of the descending motor system

Answer 2

Medial motor system

Lateral motor system

Question 3

5 Tracts in Medial Motor System

Answer 3

1. Tectospinal Tract
2. Medial vestibulospinal tract
3. Lateral vestibulospinal tract
4. Mediane\pontine reticulospinal tract
5. Lateral\medullary reticulospinal tract

Question 4

Which 3 pathways of the medial motor system are associated with MLF

Answer 4

Tectospinal tract
Medial vestibulospinal tract
Medial\pontine reticulospinal tract

Question 5

Key characteristics of all Medial Motor System tracts

Answer 5

1. Terminate bilaterally
2. Control neck & trunk movements
3. Enter anterior funiculus of spinal cord
4. Terminate only in the cervical & upper thoracic spinal cord (MLF)

Question 6

Tectospinal tract

Answer 6

Reflex hand & arm movement in response to visual & auditory stimuli

Question 7

Medial vestibulospinal tract

Answer 7

Reflex adjustment of head position in response to vestibular stimuli

Question 8

Medial\pontine reticulospinal tract

Answer 8

Allows head movement to follow eye movement

Question 9

Lateral vestibular spinal cord

Answer 9

Excites ipsilateral extensor motor neurons

Question 10

Lateral reticulospinal tract

Answer 10

Gross movements and regulates muscle tone

Controlled by corticobulbar tract

Question 11

2 tracts in the Lateral Motor System

Answer 11

1. Rubrospinal tract

2. Corticospinal tract

Question 12

Lateral motor neurons terminate on

Answer 12

lateral part of intermediate gray & motor neurons

Question 13

Rubrospinal Tract

Answer 13

Descending autonomic fibers
Respiratory control
Generalized gross movements
Regulates gamma neurons

Question 14

Corticospinal tract

Answer 14

Voluntary movement from the cortex
Regulate sensory information
Fast and highly skilled movement

Question 15

Corticospinal tract pathway

Answer 15

PIC-BMS-LF
Precentral Gyrus
Internal capsule (posterior limb)
Cerebral peduncle
Basal pons
Medullary pyramids
Decussate in the spinal cord (90%)
Lateral funiculus

Question 16

10 % of the cortical spinal cord fibers do not decussate, where do they synapse

Answer 16

Dorsal horn of spinal cord

Interneurons that control independent digits

Question 17

Originates from which nucleus

Tectospinal tract

Answer 17

Superior colliculus

Question 18

Originates from which nucleus

Medial vestibulospinal tract

Answer 18

Medial vestibular nucleus

Question 19

Originates from which nucleus

Pontine reticulospinal tract

Answer 19

PPRF

Paramedian pontine reticulospinal tract

Question 20

Originates from which nucleus

Lateral vestibulospinal nucleus

Answer 20

Lateral vestibular nucleus

Question 21

Originates from which nucleus

Lateral reticulospinal tract

Answer 21

Medulla

Question 22

Originates from which nucleus

Rubrospinal tract

Answer 22

Red nucleus in the midbrain

Question 23

Indirect corticospinal tract

3 functions

Answer 23

1. Allows cortex to control descending motor tracts that do not originate from the cortex i.e.red nucleus and superior colliculus
2. Muscle tone
3. Body stabalization

Question 24

Anticipatory maintenance of body posture before a movement is associated with

Answer 24

Indirect corticospinal tract

Question 25

Inhibits spinal cord reflexes

Answer 25

Cortico-reticulo-spinal pathway

Question 26

Corticobulbar Tracts

Answer 26

Inhibitory tracts between cortex and the brainstem | Can be used as an indirect corticospinal pathway

Question 27

Unilateral lesions of the upper motor neuron branches of CN VII (facial) result in

Answer 27

Unilateral paralysis on the contralateral side

Question 28

Unilateral lesions of CN VII branches innervating the upper face result in

Answer 28

No clinical weakness | These neurons terminate bilaterally

Question 29

Unilateral lesions of motor neuron branches of CN VII innervating lower face result in

Answer 29

Contralateral paralysis | The neurons terminate with decussation

Question 30

Unilateral lesions to the facial nerve prior to branching result in

Answer 30

Ipsilateral paralysis

Question 31

Where in the cortex is movement initiated

Answer 31

Premotor cortex

Question 32

Which part of the cortex is only activated if movement occurs

Answer 32

Primary motor cortex

Question 33

Which area of the cortex is active during rehearsal or preparation of movement

Answer 33

Premotor cortex\supplementary motor area