An insect's nervous system consists of three main parts: 1) The central nervous system is a double chain of ganglia connected by nerve fibers that control the insect's behavior and innervate its senses, muscles, and organs. 2) The visceral nervous system connects to the brain and supplies nerves to the foregut, midgut and heart. 3) The peripheral nervous system is a network of sensory cells just below the integument that detects stimuli from the environment.

1. INSECT NERVOUS SYSTEM
Prepared by
Dr. S. Sumaiya

2. NERVOUS SYSTEM
 Basic components
 Cell body:
 Soma / Perikaryon
 Contains nucleus
 Protoplasmic extension -
Axon
 Dendrites:
 Branching structure of
neuron
 Receives stimuli from
environment pass to axon
 Shorter than axon
An insect nervous system is a network of specialized
cells – Neurons

3. NERVOUS SYSTEM
 Axon (Neurite)
 The long extension of neuron that carries nerve
impulses away from the body of the cell.
 Hair like ends of the axon at the end – Terminal
arborisation
 Provided with schwanns or glial cells
 Glial cells produce myelin, located in myelin
sheath

4. TYPES OF NEURONS
A. Structural basis
i. Monopolar : neuron with a
single axon
ii. Bipolar : neuron with a
proximal axon and a long
distal dendrite.
iii. Multipolar : neuron with
a proximal axon and many
distal dendrites.

5.  B. Functional basis
 i. Sensory neuron: It conducts impulse from sense organs to
central nervous system (CNS).
 ii. Motor neuron: It conducts impulse from CNS to effector
organs
 iii. Inter neuron:(association neuron: It interlinks sensory
and motor neurons.
TYPES OF NEURONS

6. MECHANISM OF IMPULSE CONDUCTION
 Impulses are conducted by the neurons by two means.
 A. Axonic conduction: Ionic composition varies between
inside and outside of axon resulting in excitable conditions,
which leads to impulse conduction as electrical response.
 B. Synaptic conduction: Neuro chemical transmitters are
involved in the impulse conduction through the synaptic
gap. Neuro transmitters and the type of reactions helping in
the impulse conduction is as follows.
 Acetyl CO-A + Choline (choline acetylase ) Acetyl
choline
 Acetyl choline + Water (Acetyl choline esterase ) Choline
+ Acetic acid

7. NERVOUS SYSTEM
 i. Central nervous system (CNS)
 ii. Visceral nervous system (VNS)
 iii. Peripheral nervous system (PNS)

8. I. CENTRAL NERVOUS SYSTEM
 It contains double series of nerve centres (ganglia).
 These nerve centres (ganglia) are connected by longitudinal
tracts of nerve fibres called connectives and transverse
tracts of nerve fibres called commissures.
 Central nervous system is made up of the following.
 (i).Brain: Formed by the fusion of first three cephalic
neuromeres.
 Protocerebrum : Large, innervate compound eyes and ocelli.
 Deutocerebrum : Found beneath protocerebrum, innervate
antennae.
 Tritocerebrum : Bilobed, innervate labrum.
 Functions: i. Main sensory centre controls insect behaviour.

10. I. CENTRAL NERVOUS SYSTEM
 ii. Ventral nerve cord: Median chain of
segmental ganglia beneath oesophagus
 iii. Sub esophageal ganglia: Formed by
the last three cephalic neuromeres.
Innervates mandible, maxillae and
labium.
 iv. Thoracic ganglia: Three pairs found in
the respective thoracic segments, largest
ganglia, innervate legs and muscles.
 v. Abdominal ganglia: 8 pairs, number
varies due to fusion of ganglia, innervate
spiracles.
 vi. Thoracio abdominal ganglia: Thoracic
and abdominal ganglia are fused to form
single compound ganglia. Innervate
genital organs and cerci.

11. II. VISCERAL NERVOUS SYSTEM
 It is also called
stomatogastric nervous
system
 This system is connected
to brain and supplies
nerves to fore-intestine,
mid-intestine and heart
 Corpora allata, corpora
cardiaca, reproductive
organs and tracheal
system are closely
associated with this
system

12. PERIPHERAL NERVOUS SYSTEM
 It is composed of fine
network of sensory cells and
axon, which lies just below
the integument