Upper Motor Neurones and Control of Movement Flashcards
no input is needed from the motor cortex to rhythmically co-ordinate walking - true or false?
true - neuronal circuits causing flexion / extension of the legs can control this at spinal level
describe the 3 levels of motor control?
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
what areas of the brain are involved in producing a “strategy” for movement?
neocortical association area and basal ganglia
what areas of the brain are responsible for the “tactics” or a motor movement?
motor cortex
cerebellum
what parts of the CNS cause execution of the planned movement?
brain stem
spinal cord
what brodmanns area make up the motor cortex in pre-central gyrus?
brodmann areas 4+6
name the two lateral descending motor tracts and their shared function?
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)
there are various ventromedial pathways which descend the brainstem - name some examples and their main function?
ventral corticospinal
tectospinal
reticulospinal
vestibulospinal
function - control of posture and locomotion
the ventromedial pathways are under cerebral cortex control - true or false?
false
the lateral pathways are under cerebral cortex control whereas the ventromedial pathways are under brainstem control
where in the corticospinal tract does decussation of most fibres occur?
medullary pyramids
most fibres cross at pyramidal decussation to form lateral corticospinal tract - remainder stay ipsilateral to form central corticospinal tract
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?
terminate in dorsolateral region of ventral horn
associated with distal muscles, particularly flexors
where are cell bodies of the rubrospinal tract located, and where does this nucleus receive input from?
red nucleus
receives input from the motor cortex and the cerebellum
where do fibres from the rubrospinal tract decussate?
at the ventral tegmental decussation
where do fibres from rubrospinal tract terminate?
descends spinal cord ventrolateral to the lateral corticospinal tract and terminates in the ventral horn
what muscles does the rubrospinal tract control?
limb flexor muscles
if there is damage to only the corticospinal tract, then the rubrospinal tract has the potential to compensate for damage - true or false?
true
if both lateral tracts are damaged, explain the characteristics of patients movement?
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
what are the two nuclei of the vestibulospinal tract?
medial (goes to cervical region) and lateral (goes to lumbar region)
what is the function of signals descending via the lateral vestibular nucleus (deiters nucleus)?
helps to hold upright and balance posture
causes extension in antigravity muscles esp lower limb
what is the function of signals descending via the medial vestibular nucleus?
activate cervical spinal circuits (neck muscles etc)
guiding head movements
where are cell bodies of tectospinal tract found?
superior colliculus
where does the superior colliculus receive input from?
retina
visual cortex
sensory and auditory afferents
eg helps to guide eyes to new important visual stimulus
where do axons of the tectospinal tract decussate?
decussate in the dorsal tegmental decussation and descend close to the midline
what are the two parts of the reticulospinal tract and where do they arise from?
pontine (medial) and medullary (lateral)
arise from the reticular formation (diffuse mesh of neurones at the core of brainstem)
what are the functions of the medial / pontine reticulospinal tract?
enhances antigravity reflexes of the spinal cord
maintain standing posture by helping contract extensor muscles in the lower limbs
what are the functions of the lateral / medullary reticulospinal tract?
opposes the action of medial tract
releases antigravity muscles from reflex control
both of the reticulospinal tracts descend bilaterally - true or false?
false
medial / pontine descends ipsilaterally
lateral / medullar descends bilaterally
activity in both the medial and lateral reticulospinal tract is controlled by what?
descending signals from the cortex
