Renshaw cells are inhibitory interneurons which are located in the gray matter of the spinal cord. They are associated in two ways with an alpha motor neuron.
Renshaw cells receive an excitatory collateral from the alpha neuron's axon, as they monitor how vigorously that neuron is firing. They also send an inhibitory axon to synapse with the cell body of the initial alpha neuron and/or an alpha motor neuron of the same motor pool. Thus, Renshaw cell inhibition represents a negative feedback mechanism. A Renshaw cell may be supplied by more than one alpha motor neuron collateral and it may synapse on multiple motor neurons.