Histology is the study of tissues. Tissues are groups of cells that are similar in structure and function. There are four tissue types associated with animals such as humans. They are:

epithelial_tissue,

connective_tissue (CT),

muscle_tissue, and

nerve_tissue

Each of these tissue categories has distinctive cell shapes and functions.

Nerve tissue consists of two cell types: neurons and neuroglial (glial) cells. The neurons are the cells that do the job we associate with the nervous system. They are electrically excitable and can receive, process, and transmit electrical impulses. Neuroglial cells support, protect, nourish, and defend the neurons of the NS.

Research has recently revealed that glial cells also play an active role in the process of nerve impulse conduction, as well as being critical players in the formation and maintenance of memory sequences. Half the volume of the central_nervous_system (CNS) consists of glial cells.

NOTE:

(1) This slide shows a neuron and its cellular processes (axon and dendrites), as well as a backgound "blur" of glial cytoplasm.

(2) The "dots" in the background are the nuclei of glial cells.