Nerve cell. Coloured confocal light micrograph of a nerve cell (neuron, yellow) and a capillary (pink) containing red blood cells (red). The nerve cell has dendrites branching out from it. Nerve cells are responsible for relaying and processing signals in the nervous system. Signals arrive at a neuron through its dendrites. Capillaries are the smallest part of the network of blood vessels that carry blood around the body. They are only just wider than the red blood cells (erythrocytes) that carry oxygen to the body tissues. This nerve cell comes from the retina, the light-sensitive part of the eye. Magnification unknown.