Insect nervous system

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