Basic Concepts in the Control of Movement Flashcards
Motor control
ability to regulate or direct mechanisms essential to
movement.
Motor learning/adaptation generally refers to the
neuronal changes that occur to allow an individual to accomplish a new motor task, to perform a task better, faster or more accurately than before usually
refers to motor adaptation.
How are movements organised by the CNS to achieve
behavioural goals?
- CNS predicts -> feedforward motor/postural command
- Activates aMN’s in SC -> innervate muscles required to execute task
- Resultant movement generates sensory feedback used to correct errors
- Update plan
Movement ability depends on
CNS development and experience
Primary categories of movement
- Reflex
- Rhythmical
- Voluntary
What are the 2 basic types of motor activity?
Ballistic and guided by feedback
Ballistic movement characteristics
- Forward model
- Open-loop
- Problems with accuracy but fast
- Useful for well-known tasks
- Updated through learning
Guided by feedback characteristics
- Feedback model
- Closed-loop
- Accurate but problems with delay
- Useful for novel tasks
- Enables learning
General model by which tasks are carried out
Idea, Plan, Execution, Appraisal
3 types of control
Feedforward, feedback, biomechanical control (modulation of limb compliance)
Forward model vs feedback system
- Timing of sensory feedback: at least 50ms to get to sensorimotor areas of the brain and back to the
spinal cord and muscle to adjust output. - Forward model/ feedforward command can initiate action on the basis of prediction.
What are 2 basic models of motor control?
‘Servo’model i.e. feedback + Optimal feedback control
How are motor tasks organised?
Movements occur on a continuum of automatic to voluntary
2 main functions of muscles:
- Generate power -> recruitment of motor units
2. Sensory information -> receptors that modulate muscle activation
Proprioceptor
Any type of receptor which gives information about body position or movement e.g. primary muscle spindles, GTO
Where are muscle spindles in relation to muscle fibres?
Muscle spindles (proprioceptors): intrafusal muscle fibres attached at the end of extrafusal muscle fibres that envelop it and lie in parallel with the muscle fibres
What type of muscle fibres make up the intrafusal portion of the muscle spindle?
Dynamic (bag) and static nuclear bag -> signals phasic and tonic aspects of muscle stretch
Muscle spindle primary afferents are called ____ and arise from ____
Type 1a (large diameter) , arise from all intrafusal fibre types
Muscle spindle secondary afferents are ____ and arise from ____
Type 2 ( medium diameter), from static fibres
Muscle spindle sensitivity
controlled by the gamma (γ) efferent system
Position of joints is determined by
Muscle length
What is the role of the stretch reflexes in the control of
movement?
Feedback mechanism: responds and makes adjustments to small changes in length at the spinal cord level during contractions against loads, for unexpected disturbance and for stabilisation during postural activity, by reflexive corrections (Aniss et al 1990) and transmits signals about length and rate of change in length to supraspinal areas
Why is the stretch reflex important (4 points)?
- Muscle spindle is the sensory receptor for the reflex
- Stretch reflex can be modulated by descending pathways & other inputs
- Circuitry results in innervation of agonist & antagonist muscles
- Useful to study the excitability of the α MN
What are golgi tendon organs?
Proprioceptors: encapsulated receptors which lie at the junction between muscle fibres and tendons (musculo-tendinous junction): lie in series in the muscle that are sensitive to changes in muscle tension
