Control of movement
Co-ordination and control of movement
The pyramidal system communicates the conscious decision to mobilise the body
but there are various mechanisms that control, co-ordinate and stabilise the
movement pattern.
Involves various simple reflexes and complex higher interactions.
Uses various sensori-motor feedback systems involving CNS and different levels
of motor system
Practical examples
- Maintaining gait or balance despite shifting centre of gravity e.g.
uneven or moving walking surface, pace of walking/running remains constant
- Limb position or rate of movement remains relatively constant despite
changing loads (e.g. weight shifting in grip, sudden force applied to arm
whilst lifting)
- Activating primer mover (agonist) e.g. biceps whilst relaxing antagonist
e.g. tricep and maintaining stabilisers (synergist) e.g. rotator cuff when
lifting an object
Simple system
- Muscle spindles (control of muscle contraction in respond to changes in
length and stretch of muscle belly)
- Spinal cord reflex (control of muscle contraction in response to tendon
stretch)
ensures smooth movement throughout contraction/shortening or
relaxation/lengthening
Complex systems
- Proprioceptive - control of posture and balance from cutaneous and joint
position inputs
- Extra-pyramidal - simulataneous relaxation / lengthening of antagonist
muscles during contraction / shortening of agonist muscles
- Cerebellar - co-ordination, fine control and balance
- Vestibu-ocular (stabilisation of eye movements and balance in response
to changes in head or body position)
Clinical relevance
- Disturbances to movement may the result of not only components of the
motor systems but also to sensory ones as well.
- Specific clinical patterns are observed depending on the location of the
lesion.
Clinical examples
- Parksinson's disease - shuffling gait (feet glued to floor),
accelerating (festinant) gait - centre of gravity moving forward faster than
feet, resting tremor and cogwheel rigidity where agonist/antagonist groups
don't contract/relax in synchrony ('brake and accelerator on together'
leading to slowed / small movements)
- Cerebellar disease - intention tremor - fine tuning of voluntary
movements become worse as the limb approaches the target object,
dysdiachokinesis - unable to rapidly switch between two opposing movements
e.g. forearm pronation/supination (problems with activation/deactivation
agonist/antagonist muscle groups)
- Sensory ataxia - high stepping gait due to inability to feel lower limbs
touching or hitting the ground