Although the focus of this article is the neuron, a neuron does not exist in isolation nor can it properly be described in the singular, because its interactions and associations with other neurons, glia, and target cells are integral to its function.

That distinction belongs to a second class of cells called the neuroglia or simply glia. The neuron is the fundamental anatomical building block of the neuronal circuits underlying behavior, but it is not the only cell type in the nervous system nor indeed the most numerous. Neurons are unique among cells in their large size, complexity, and the diversity of their forms, which are closely related to the functions they subserve. The term neuron was coined by the German neuroanatomist Wilhelm Waldeyer in 1891. The neuron is a member of the class of cells most closely identified with the functions of the nervous system, namely, the transduction, processing, storage, and translation of environmental information into meaningful behaviors. Ellisman, in Encyclopedia of the Human Brain, 2002 I Introduction

The synaptic secretion is then different (with only a few exceptions) from other secretory cells, such as from hormonal and exocrine cells which respectively release their secretory products into the general circulation (endocrine secretion) or the external environment (exocrine secretion). The synaptic secretion is highly focalized and directed specifically on cell regions to which the neuron is connected. The neurotransmitter is released in the extracellular space. The release of a neurotransmitter occurs only in restricted regions, the synapses. Their secretory product is called a neurotransmitter. This capacity is due to the presence of particular proteins in their plasma membrane which allow the selective passage of ions: the ion channels. Depending on the information they receive, neurons generate electrical signals and propagate them along their processes. The neurons connected together form circuits, and so the nervous system is composed of neuronal networks which transmit and process information. Neurons are independent cells making specific contacts called synapses, with hundreds or thousands of other neurons sometimes greatly distant from their cell bodies. Constance Hammond, in Cellular and Molecular Neurophysiology (Fourth Edition), 2015 Abstract

Neuron in the brain