The nervous system is an information processing and conducting system ensuring the rapid functioning and coordination of effectors, producing and modifying the insect's responses to the input from peripheral sense organs. The sensory systems are considered in Chapters 22–24, and the stomodeal system, regulating gut activity, is described in section 3.1.5. This chapter discusses the basic structure and functioning of neural elements, and the anatomy and functioning of the central nervous system.

Review: Burrows, 1996 – locust central nervous system

BASIC COMPONENTS

Neuron

The basic element in the nervous system is the nerve cell, or neuron (Fig. 20.1). This consists of a cell body containing the nucleus from which one or more long cytoplasmic projections extend to make contact with other neurons or with effector organs, principally muscles. The cell body is called the soma or perikaryon. It contains abundant mitochondria, Golgi complexes and rough endoplasmic reticulum. Information is conducted from one cell to another along the processes of the neuron. Usually, one of the processes, called the dendrite, is specialized for the reception of information. It may arise directly from the soma or as a branch from a major projection of the cell. Input directly to the soma rarely occurs in insects. The branch of the cell which carries information to other cells is usually much longer than the input branch; it is called the axon. In the central nervous system it is common for both dendrites and axon to branch extensively; they are said to arborize.