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Nervous System

In common with other animals, the basic component of the nervous system is the neurone, or nerve cell which consists of a cell body with two extensions, the axon and the dendrite. The dendrite receives stimuli while the axon transmits impulses either to another neurone or to an organ such as a muscle. Various chemicals such as acetylcholine are involved in the transmission of impulses across the synapse.

The insect central nervous system consists of a brain, suboesophageal ganglion and a ventral nerve chord.

The ventral nerve chord primitively consists of ganglia (aggregations of nerve tissue) joined by a pair of longitudinal nerve chords. Various nerves extend from these ganglia to other organs (see A in Figure E.).

Primitively there is a pair of ganglia per body segment (see A in Figure E) but there has been progressive fusion of ganglia both within and between segments (see B and C in Figure E).

The three pairs of fused ganglia of the head region, form the brain.

The three pairs of ganglia from the segments bearing the mouthparts have coalesced to form the suboesophageal ganglion.

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