Upper Motor Neurones and Control of Movement

Question 1

no input is needed from the motor cortex to rhythmically co-ordinate walking - true or false?

Answer 1

true - neuronal circuits causing flexion / extension of the legs can control this at spinal level

Question 2

describe the 3 levels of motor control?

Answer 2

strategy - aim of the movement? how can it best be achieved?

tactics - what sequence of muscle contractions and relaxations will fulfil the strategic aim?

execution - activation of neurones which command the desired movement

Question 3

what areas of the brain are involved in producing a “strategy” for movement?

Answer 3

neocortical association area and basal ganglia

Question 4

what areas of the brain are responsible for the “tactics” or a motor movement?

Answer 4

motor cortex

cerebellum

Question 5

what parts of the CNS cause execution of the planned movement?

Answer 5

brain stem

spinal cord

Question 6

what brodmanns area make up the motor cortex in pre-central gyrus?

Answer 6

brodmann areas 4+6

Question 7

name the two lateral descending motor tracts and their shared function?

Answer 7

lateral corticospinal tract + rubrospinal tract

function:

• voluntary control of distal musculature
• particularly discrete, skilled movements
• involved in fractioned movement (lots of different muscles making different movements at the same time)

Question 8

there are various ventromedial pathways which descend the brainstem - name some examples and their main function?

Answer 8

ventral corticospinal
tectospinal
reticulospinal
vestibulospinal

function - control of posture and locomotion

Question 9

the ventromedial pathways are under cerebral cortex control - true or false?

Answer 9

false

the lateral pathways are under cerebral cortex control whereas the ventromedial pathways are under brainstem control

Question 10

where in the corticospinal tract does decussation of most fibres occur?

Answer 10

medullary pyramids

most fibres cross at pyramidal decussation to form lateral corticospinal tract - remainder stay ipsilateral to form central corticospinal tract

Question 11

where do axons of the lateral corticospinal tract terminate in the ventral horn of the spinal cord, and what muscles does this associate them with?

Answer 11

terminate in dorsolateral region of ventral horn

associated with distal muscles, particularly flexors

Question 12

where are cell bodies of the rubrospinal tract located, and where does this nucleus receive input from?

Answer 12

red nucleus

receives input from the motor cortex and the cerebellum

Question 13

where do fibres from the rubrospinal tract decussate?

Answer 13

at the ventral tegmental decussation

Question 14

where do fibres from rubrospinal tract terminate?

Answer 14

descends spinal cord ventrolateral to the lateral corticospinal tract and terminates in the ventral horn

Question 15

what muscles does the rubrospinal tract control?

Answer 15

limb flexor muscles

Question 16

if there is damage to only the corticospinal tract, then the rubrospinal tract has the potential to compensate for damage - true or false?

Answer 16

true

Question 17

if both lateral tracts are damaged, explain the characteristics of patients movement?

Answer 17

less fractionated - all muscles trying to do same thing at same time, movement is larger and less accurate and also slower

little effect on normal posture

Question 18

what are the two nuclei of the vestibulospinal tract?

Answer 18

medial (goes to cervical region) and lateral (goes to lumbar region)

Question 19

what is the function of signals descending via the lateral vestibular nucleus (deiters nucleus)?

Answer 19

helps to hold upright and balance posture

causes extension in antigravity muscles esp lower limb

Question 20

what is the function of signals descending via the medial vestibular nucleus?

Answer 20

activate cervical spinal circuits (neck muscles etc)

guiding head movements

Question 21

where are cell bodies of tectospinal tract found?

Answer 21

superior colliculus

Question 22

where does the superior colliculus receive input from?

Answer 22

retina
visual cortex
sensory and auditory afferents

eg helps to guide eyes to new important visual stimulus

Question 23

where do axons of the tectospinal tract decussate?

Answer 23

decussate in the dorsal tegmental decussation and descend close to the midline

Question 24

what are the two parts of the reticulospinal tract and where do they arise from?

Answer 24

pontine (medial) and medullary (lateral)

arise from the reticular formation (diffuse mesh of neurones at the core of brainstem)

Question 25

what are the functions of the medial / pontine reticulospinal tract?

Answer 25

enhances antigravity reflexes of the spinal cord

maintain standing posture by helping contract extensor muscles in the lower limbs

Question 26

what are the functions of the lateral / medullary reticulospinal tract?

Answer 26

opposes the action of medial tract

releases antigravity muscles from reflex control

Question 27

both of the reticulospinal tracts descend bilaterally - true or false?

Answer 27

false
medial / pontine descends ipsilaterally
lateral / medullar descends bilaterally

Question 28

activity in both the medial and lateral reticulospinal tract is controlled by what?

Answer 28

descending signals from the cortex