Figure 19

Schematic representation of different types of neurons (modified from various sources). A. Unipolar neuron and terminology of different cell parts. B. Bipolar neuron. C. Pseudounipolar neuron. D, E, F. Multipolar neurons of different morphology. G. Bipolar receptor cell sending its axonal processes into an intraepidermal plexus. H, I. Bipolar receptor cells with a short distal (dendritic) process and with a soma embedded in the epithelium. Most common type in invertebrates. J. Bipolar receptor cell with elaborated distal process (arthropod scolopale). K, L. So-called free nerve endings with bipolar (K) and unipolar receptor cells as in vertebrates (L). M. Receptor cell showing a bipolar form connected by its dendritic processes with a group of epithelial cells specialized as receptor elements (so-called secondary sensory cells). Modified from [18], with permission of Freeman.