The insect nervous system consists of three main parts: the central nervous system (CNS), the visceral nervous system, and the peripheral nervous system. The CNS contains a brain and a ventral nerve cord made up of fused ganglia. It receives and processes sensory information. The visceral nervous system innervates internal organs. The peripheral nervous system connects the CNS and visceral nervous system to muscles and sense organs via motor and sensory neurons. Together these systems allow insects to respond to their environment and control bodily functions through neural pathways and chemical signaling between different neuron types.

1. Kingdom of Saudi Arabia
Al Imam Mohammad Ibn Saud Islamic University
College of Science
Department of Biology
Entomology
353 Bio
T. Amani Alsharidah
1441 – 2019

2. lecture 10
Insect Nervous system

3. Insect Nervous system
 The basic component is the nerve cell, or neuron (neurone), composed of a cell
body with two projections (fibers):
1. The dendrite, which receives stimuli.
2. The axon, which transmits information, either to another neuron or to an
effector organ such as a muscle.
 Insect neurons release a variety of chemical at synapses to either stimulate or
inhibit effector neurons or muscles.
 In common with vertebrates, particularly important neurotransmitters include
acetylcholine and catecholamines.

4. Type of neuron
1. Sensory neurons:
Receive stimuli from the insect’s environment and transmit them to the central
nervous system.
2. Interneurons (or association neurons):
Receive information from and transmit it to other neurons.
3. Motor neurons:
Receive information from interneurons and transmit it to muscles.
4. neuroendocrine cells:
The cell bodies of interneurons and motor neurons are aggregated with the
fibers interconnecting all types of nerve cells to form nerve centers called
ganglia.

5. Diagram of a simple reflex mechanism of an insect.
The arrows show the paths of nerve impulses along nerve fibers (axons and dendrites).

6. The insect nervous system
1. Central nervous system.
2. Visceral nervous system.
3. Peripheral nervous system.

7. 1. Central nervous system
 The central nervous system (CNS) is the principal division
of the nervous system and consists of series of ganglia
joined by paired longitudinal nerve cords called
connectives.
 Primitively there are a pair of ganglia per body segment
 The ganglia of all head segments are coalesced to form two
ganglionic centers:
 The brain and the suboesophageal (subesophageal)
ganglion.
 The chain of thoracic and abdominal ganglia found on the
floor of the body cavity is called the ventral nerve cord.

8. The brain
 The brain, or the dorsal ganglionic center of the head, is composed of three
pairs of fused ganglia (from the first three head segments):
1. protocerebrum:
Associated with the eyes and thus bearing the optic lobes;
2. Deutocerebrum:
Innervating the antennae
3. Tritocerebrum:
Concerned with handling the signals that arrive from the body.

9. 2. Visceral nervous system
Consists of three subsystems:
1. The stomodeal (or stomatogastric)
which includes the frontal ganglion.
2. The ventral visceral
3.The caudal visceral.
Together the nerves and ganglia of these subsystems innervate the anterior
and posterior gut, several endocrine organs, the reproductive organs, and the
tracheal system including the spiracles.

10. 3. The peripheral nervous system
Consists of:
1. All of the motor neuron axons that radiate to the muscles from the
ganglia of the CNS, stomodeal nervous system.
2. The sensory neurons of the cuticular sensory structures (the sense
organs) that receive mechanical, chemical, thermal, or visual stimuli from
an insect’s environment.