neuromuscular Flashcards
What is a motor unit?
A motor unit consists of a motor neuron and all the muscle fibres it innervates.
What is the all-or-none law?
hen a motor unit is stimulated, all muscle fibres contract fully or not at all.
What is the role of the motor neuron?
To carry an electrical impulse from the central nervous system to the muscle fibres, triggering contraction.
What is spatial summation?
Increasing the number of motor units recruited to increase the force of contraction.
What is wave summation?
When repeated impulses are sent before the muscle has relaxed, leading to a sustained contraction.
What is tetanic contraction?
A smooth, sustained contraction caused by high-frequency stimulation of motor units.
Name the three types of muscle fibres
Type I (slow oxidative)
Type IIa (fast oxidative glycolytic)
Type IIb (or IIx) (fast glycolytic)
Characteristics of Type I fibres?
Slow contraction speed
High resistance to fatigue
Use oxygen (aerobic)
Best for endurance activities (e.g., marathon)
Characteristics of Type IIa fibres?
Fast contraction speed
Moderate fatigue resistance
Use both aerobic and anaerobic systems
Best for middle-distance activities (e.g., 800m)
Characteristics of Type IIb (IIx) fibres?
Very fast contraction speed
Low fatigue resistance
Anaerobic, high force output
Best for explosive activities (e.g., sprinting)
Which fibres are recruited first during activity?
Type I are recruited first (low threshold), followed by Type IIa, then Type IIb as intensity increases.
What is a proprioceptor?
A sensory receptor that provides information about body position and movement, aiding coordination.
What is the role of the muscle spindle?
Detects changes in muscle length and triggers the stretch reflex to prevent overstretching.
What is the Golgi tendon organ (GTO)?
Detects tension in the tendon and can inhibit contraction if force is too great – promoting relaxation.
What is the stretch reflex?
A protective response where a muscle contracts to prevent overstretching, triggered by muscle spindles.
Name two neural adaptations to strength training.
Increased recruitment of motor units
Faster nerve impulse transmission
Improved motor unit synchronization
Name two muscular adaptations to training.
Hypertrophy of muscle fibres
Increased stores of ATP and PC
Greater tolerance to lactic acid in Type II fibres
What causes improved strength without muscle growth in early stages of training?
Neural adaptations (better recruitment and coordination), not hypertrophy.
Which type of fibre shows the most hypertrophy from anaerobic training?
Type IIb (fast glycolytic fibres) – due to high-force, explosive activities.
How does endurance training affect muscle fibres?
Increases mitochondrial density
Enhances capillarisation
Improves oxidative enzyme activity in Type I fibres
