Neuromuscular diseases

Skeletal muscles represent around 40% of the body and their contractions enable movement including essential human behaviour such as breathing, eating, walking, and speaking. They are composed of long muscle fibre cells that extend from tendon to tendon, and they can be several centimetres long. The activity of muscle is controlled by the nervous system and each muscle fibre receives input from the nervous system at a small area of the muscle fibre. This specialized membrane area is known as the neuromuscular junction.

Intention to move is initiated by the generation of electrical signals in the brain that travel from the brain through both an upper and a lower motor neuron before arriving at the neuromuscular junction. At this junction, electrical signal in motor neurons must be transmitted to similar electrical signals in the muscle fibes via a process known as neuromuscular transmission. The resulting electrical signals in the muscle fibres travel along the muscle fibres length to trigger an elevation in Ca2+ in the muscle that in turn triggers force production by contractile proteins.

Neuromuscular diseases represent a broad range of disease characterized by muscle weakness and excessive fatigue. Muscle weakness and fatigue can arise at any of the steps in the activation of muscle fibres. The neuromuscular junction is known to be involved in multiple neuromuscular disorders and compromised transmission at the neuromuscular junction underlies failing muscle fibre activation in several diseases.