Neuromuscular Function

Topic 4.1

Motor Unit

A single motoneuron and the muscle fibres which it innervates

Motoneurons

The nerves that carry signals to the central nervous system from receptors. Sometimes called afferent neurons.

Neurotransmitters

Chemicals that are used for communication between a neuron at the synapse and another cell

Acetylcholine

A chemical that transfers the action potential from the motor unit to the muscle cells, allowing a muscle to contract

Cholinesterase

An enzyme that breaks down acetylcholine

Action Potential

The rapid changes in charge across the membrane that occur when a neuron is firing

Myofibril

Tightly packed filament bundles within the skeletal muscle fibres

Myofilament

The filaments of myofibrils.

Tropomyosin

An actin-binding protein, that covers the myosin binding sites on actin

Troponin

A protein that is a calcium receptor causing tropomyosin to shift and expose the binding sites

Sliding filament theory

Action and myosin filaments slide past each other to shorten the muscle during contraction, which produces tension.

Explain the features of type one muscle fibres

• Slow contraction speed

• High resistance to fatigue

• Lots of mitochondria

• Low force production

• Aerobic activity

  • e.g. triathlon

Explain the features of type two A muscle fibres

• Fast contraction speed

• Intermediate resistance to fatigue

• Lots of mitochondria

• High force production

• Long, anaerobic activity

  • e.g. 800m sprint, javelin

Explain type two B muscle fibres

• Very fast contraction speed

• Low resistance to fatigue

• Less mitochondria

• Very high force production

• Short anaerobic activity

  • e.g. 200m freestyle swim

What is a muscle biopsy

The removal of muscle cells from a specific muscle tissue in order to detect potential diseases involving muscle tissues W

What are some positives of muscle biopsies

• Accurate diagnosis

• Allows a scientific understanding

• Helps monitor treatment

What are some negatives of muscle biopsies

• Physical discomfort

• Ethical concerns

• Expensive

• Invasive

• Limited accessibility