Sarah Etherington

The neuromuscular junction (NMJ) is the site of communication between motor nerve axons and muscle fibres. It is composed of four specialised cell types: motor neurons, Schwann cells, muscle fibres and the recently discovered kranocytes. The function of the NMJ is to transmit signals from the motor neuron to the skeletal muscle fibre quickly and reliably, to ensure precise control of skeletal muscle contraction and therefore voluntary movement. The reliability of transmission is aided by specialised architecture (multiple active zones, junctional folds) that promotes high levels of transmitter release, large and reliable postsynaptic responses to transmitter binding and rapid termination of signalling events. In the last century, the structure and function of the NMJ has been extensively studied, which has been instrumental in uncovering many of the fundamental processes of chemical synaptic transmission.

Neurons in the brain receive thousands of synaptic inputs from other neurons. Synaptic integration is the term used to describe how neurons ‘add up’ these inputs before the generation of a nerve impulse, or action potential. The ability of synaptic inputs to effect neuronal output is determined by a number of factors, including the size, shape and relative timing of electrical potentials generated by synaptic inputs, the geometric structure of the target neuron, the physical location of synaptic inputs within that structure, as well as the expression of voltage-gated channels in different regions of the neuronal membrane. The process of synaptic integration is therefore modulated at multiple levels, contributing to the diverse and complex computational powers of the functioning brain.