Chapter 11 - Nervous Systems

Abstract

Insects use both the endocrine and the nervous systems for information transfer between their cells, with each system having its own advantages and constraints. Biological information transmitted by the electrical signals of the nervous system provides a much more rapid means for coordinating cellular events than that transmitted by hormones or chemical messengers. This chapter examines aspects of nervous transmission in insects. Nerve cells, or neurons, are the cellular building blocks that make up the nervous system. They are capable of integrating information, undergoing excitation, and transmitting the information by electrical and short-range chemical signaling. Maintenance of electrical potential in dendrites of neurons help in neural transmission. A number of different neurotransmitters and neuromodulators are involved in nervous transmission at both invertebrate and vertebrate synapses. The synaptic connection of a single neuron with two or more neurons, or with a muscle cell innervated by multiple motor neurons that includes neurotransmitters capable of exciting or inhibiting at the synapse, allows the nervous system to integrate nervous transmission in a much more complex fashion. The insect central nervous system consists of the brain and ventral nerve cord. The system comprises the individual neurons that are associated in functional groupings that evolved together with a reorganization of the insect body from its primitive annelid-like ancestor. The peripheral nervous systeminvolves all the nerves that radiate from the central nervous system. These include the nerves that innervate muscles, stretch receptors that may serve as proprioreceptors, innervations of the reproductive system and spiracles, and the various sensory receptors. Another part of the insect nervous system, termed visceral nervous system, innervates the gut, heart, and endocrine glands and forms a network of peripheral ganglia that is associated with digestive processes.