ENT

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)