The nervous system is composed of specialized nerve cells called neurons that form pathways for information transmission. Neurons produce and propagate electrical impulses along their axons and dendrites. At junctions called synapses, neurons transmit signals to one another via chemical messengers called neurotransmitters. The central nervous system of insects consists of a brain connected to a ventral nerve cord made up of ganglia. The nervous system coordinates the body, provides sensory input, and enables rapid responses through its transmission of signals from receptors to effectors like muscles and glands.

1. The Nervous system

2. Nervous system
 Network of specialized cells-Neuron
 Serve as information pathway
Neuron
 Produces electrical impulses
 Impulses travels as waves of depolarization
 Consists of nerve cell body- Where the
nucleus found and filament (Dendrites,
axons or collaterals)-Propagate the action
potential

3. Types of Neuron on the basis of number of extensions

4. Types of Neuron on the basis of their functions
1. Afferent (Sensory)
 Bipolar or multipolar
 Associated with sense organs or receptors
 Carry information towards central nervous
system (CNS)
2. Efferent (Motor)
 Unipolar
 Carry signals away from the CNS
 Stimulate responses in muscles and gland

5. 3. Internuncial (association)
 Unipolar
 Conduct signals within central nervous system

6. Neuron-Neuron Junction: Synapse
 The junction where the nerve cells become
connected- Synapses
 Nerve impulse at synapses- Releases
chemical messengers (Neurotransmitter
substance)
Diffuse-synapses (old impulse)
Triggers-new impulse in the dendrites (with one or
more connecting neurons)
Neurotransmitter substance- Acetylcholine, 5-
hydroxytryptamine, dopamine, noradrenaline

7. Nerve cells
 Typically grouped in bundles
 Bundle of dendrites or axons
Ganglion
 Dense cluster of interconnected neurons
 Process sensory information
 Control motor outputs

8. Central Nervous system (CNS)

9.  Simple
 Organized by dorsal brain linked to ventral nerve cord
consists of paired segmental ganglia
 Ganglia running along the ventral midline of the thorax and
abdomen
CNS: brain+ ventral nerve cord

10. Brain
 A compound ganglion,
major association centre
Ventral Nerve cord
 SG+TG+AG
SG
 A compound ganglion
(mandible, maxillae and
labium)

17. Functions of nervous system
 To provide for coordination of events involving most of the other systems that are
under nervous control
 To provide for the feedback from various parts of the insect that then can impact
the central nervous system
 To act as the windows of the insect by providing sensory input from the various
sense organs, sensilla, receptors or better known as the affectors
 Provide rapid response and feedback from its peripheral receptors
 Rapid transfer of information concerning short-term events and also the
coordination of these short-term events
 Transfers of messages to the effectors (i.e., muscles and glands)