Generation of Responses in Receptor

Receptors are specialized nerve cells and share with them a number of important properties. Therefore, a brief description of the general features of nerve cells may be useful as an introduction to the study of receptors. A diagram of a nerve cell and its connections is shown in Fig. 1. The cell includes a dendritic tree, the soma, the axon and terminal branches. In vertebrates, synaptic contacts occur mostly at the soma and dendrites; in invertebrates they may be located at the axon. In both vertebrates and invertebrates, dendrites may be absent. The axon can be over 1 m long, but in many cells it is so short (about 1 mm) that it cannot be easily distinguished from the dendritic branches (Golgi, 1883).