Motor Systems and Control Practice Flashcards

Comprehensive vocabulary flashcards covering motor control strategies, muscle fibre types, hierarchical organization, and key physiological principles from the lecture transcript.

Complexity (Motor Control)

The condition where movement results from many stages of processing between sensory input and muscle activation rather than a direct brain-to-muscle command.

Population coding

The phenomenon where movement is produced by the combined activity of many neurons rather than one neuron acting alone.

Feedback

Sensory information used to compare intended movement with actual movement to detect and correct errors.

Hierarchical organisation

The distribution of motor control across different levels (cortex, basal ganglia, cerebellum, brainstem, spinal cord) that specialise in different tasks.

Central Pattern Generator (CPG)

A neural network capable of producing rhythmic motor output (like walking or scratching) without requiring a separate command for every cycle.

Motor unit

One alpha-motoneuron and every muscle fibre it innervates; identified as the final common pathway for all movement.

Henneman’s Size Principle

The principle that motor units are recruited from smallest to largest as force demand increases.

Common drive

A hypothesis by De Luca & Erim stating that motor units receive one shared synaptic command rather than individual commands.

Internal model

A neural representation or prediction of movement outcome generated before sensory feedback arrives.

Efference copy

A copy of the outgoing motor command sent to an internal model to predict the consequences of movement.

Forward model

A type of internal model that predicts the sensory consequences of a specific motor command.

Inverse model

A type of internal model that calculates the motor command needed to achieve a desired movement goal.

Ballistic control

A pre-planned movement executed rapidly without the use of sensory correction during the movement itself.

Guided feedback control

A control strategy involving continuous comparison between intended and actual movement with ongoing corrections.

Parametric feedback

A strategy where a movement is ballistic, but sensory errors are used after the movement finishes to improve future performance.

Synaptic efficacy

A concept described by Burke referring to the effectiveness of synaptic input at influenced motoneuron firing, determined by factors like neurotransmitter release and dendritic location.

Inverse kinematics

The computational process of calculating joint movements needed to reach a specific target.

Inverse dynamics

The computational process of calculating the muscle forces required to produce a specific movement.

Type I Fibres

Slow oxidative muscle fibres characterized by slow contraction, low force, and high fatigue resistance.

Type IIa Fibres

Fast oxidative-glycolytic muscle fibres that produce moderate force and have moderate fatigue resistance.

Type IIx Fibres

Fast glycolytic/fast fatigable fibres that produce the highest force but fatigue quickly.

Rate coding

The process of changing the firing frequency of active motor units to adjust muscle force.

Tetanus

A sustained muscle contraction produced by very high firing frequencies of action potentials.

Ohm’s Law ($V = IR$)

The physical law explaining why small motoneurons are recruited first; their higher input resistance ($R$) results in a larger depolarisation ($V$) for the same synaptic current ($I$).

Mendell et al.

Researchers who demonstrated that motoneuron electrical properties are matched to the specific characteristics of the muscle fibres they innervate.

Schiaffino & Reggiani

Researchers who described the molecular basis of muscle fibre diversity through different myosin heavy-chain isoforms.