Protocerebrum: The first pair of ganglia are largely associated with vision they innervate the compound eyes and ocelli.Each part of the brain controls (innervates) a limited spectrum of activities in the insect’s body: In more “advanced” insect orders there is a tendency for individual ganglia to combine (both laterally and longitudinally) into larger ganglia that serve multiple body segments.Īn insect’s brain is a complex of six fused ganglia (three pairs) located dorsally within the head capsule. In general, the central nervous system is rather ladder-like in appearance: commissures are the rungs of the ladder and intersegmental connectives are the rails. Ganglia within each segment are linked to one another by a short medial nerve ( commissure) and also joined by intersegmental connectives to ganglia in adjacent body segments. Like most other arthropods, insects have a relatively simple central nervous system with a dorsal brain linked to a ventral nerve cord that consists of paired segmental ganglia running along the ventral midline of the thorax and abdomen. Side view of body showing relative position of circulatory (yellow), digestive (green), and nervous (blue) systems. A ganglion is a dense cluster of interconnected neurons that process sensory information or control motor outputs. A nerve is simply a bundle of dendrites or axons that serve the same part of the body. Nerve cells are typically found grouped in bundles. Acetylcholine, 5-hydroxytryptamine, dopamine, and noradrenaline are examples of neurotransmitters found in both vertebrate and invertebrate nervous systems. When a nerve impulse reaches the synapse, it releases a chemical messenger ( neurotransmitter substance) that diffuses across the synapse and triggers a new impulse in the dendrite(s) of one or more connecting neurons. Individual nerve cells connect with one another through special junctions, called synapses. Internuncial (association) neurons - unipolar cells (often with several collaterals and/or branching axons) that conduct signals within the central nervous system.Efferent (motor) neurons - unipolar cells that conduct signals away from the central nervous system and stimulate responses in muscles and glands.They always carry information toward the central nervous system. Afferent (sensory) neurons - these bipolar or multipolar cells have dendrites that are associated with sense organs or receptors.Neurons are usually divided into three categories, depending on their function within the nervous system:

Signal transmission is always unidirectional - moving toward the nerve cell body along a dendrite or a collateral and away from the nerve cell body along an axon. Every neuron has a nerve cell body (where the nucleus is found) and filament-like processes ( dendrites, axons, or collaterals) that propagate the action potential. These cells generate electrical impulses (action potientials) that travel as waves of depolarization along the cell’s membrane. An insect’s nervous system is a network of specialized cells (called neurons) that serve as an “information highway” within the body.

Dendrite definition action potential