The Physiology of Insecta

Volume IV

Morris Rockstein

• Publisher: Academic Press
• Year: 2013
• Print ISBN: 9780125916042
• eBook ISBN: 9781483276700
• Topic: Biological Sciences
• Subtopic: Zoology
• Index: Biological Sciences

The Physiology of Insecta, Second Edition, Volume IV, is part of a multivolume treatise that brings together the known facts, the controversial material, and the many still unsolved and unsettled problems of insect physiology. Since the first edition of this multivolume treatise was published, there has been a notable expansion of scientific endeavor in each of the various aspects of insect physiology. The original three-volume work has now grown to a thoroughly revised six-volume treatise. The book contains six chapters and opens with a discussion of the insect central nervous system. This is followed by separate chapters on axonal and synaptic pharmacology; the neural control of skeletal muscle; the structural proteins in insect muscle and their physico-chemical properties; biological oxidation and energetics in insects; and protein synthesis in insects.

The Insect and the Internal Environment—Homeostasis—I

Chapter 1

NEURAL INTEGRATION (CENTRAL NERVOUS SYSTEM)^*

F. Huber

Publisher Summary

Insects as multicellular and highly organized animals have developed two systems for the integration and coordination of cellular and organ functions: (1) the nervous system and (2) the endocrine system. Both consist of cellular units and communication between them and other body cells is an essential feature of insect life. The two systems are responsible for adjusting the animal to rapid and slow environmental changes. They are connected structurally and functionally by the responsiveness of neurons to humoral factors and in taking over the secretory function from cells belonging to the nervous system and initiating the release of hormones by nervous commands. Therefore, neurosecretory cells are believed to be a link between nervous and endocrine elements and were found to possess neuronal and endocrine properties in an earlier study. This chapter discusses some of the aspects of integrative activity taking place in insect nervous systems. It focuses on some of the functions of its central part in the control of behavioral activities.

I. Introduction

II. Levels and Principles of Neural Integration

III. Methods of Studying Neural Integration in Insects

IV. Structural Basis of the Insect Nervous System

A. General Topography

B. Organization of an Insect Ganglion

C. Neuronal Geometry

V. Integration at the Neuronal Level

A. Electric Properties of Insect Neurons

B. Synaptic Transmission in Insects

VI. Integration at the Multineuronal Level

A. Endogenous Activity of the Central Nervous System

B. Functional Connections of Neurons in the Cord

C. Electric Activity of Neurons in the Brain

VII. Coordination of Movements and Behavior

A. Evasive Behavior: New Aspects

B. Locomotor Activity

C. Sound Production in Insects

VIII. Neural Basis of Habituation and Learning

A. Habituation

B. Learning and Memory

IX. General Conclusions

References

I Introduction

Insects as multicellular and highly organized animals have developed two systems for the integration and coordination of cellular and organ functions: the nervous system and the endocrine system. Both consist of cellular units and communication between them and other body cells is an essential feature of insect life. The two systems are responsible for adjusting the animal to rapid and slow environmental changes. They are closely connected structurally and functionally, as shown, for instance, by the responsiveness of neurons to humoral factors (Milburn et al., 1960; Roeder et al., 1960; Milburn and Roeder, 1962), and in taking over the secretory function from cells belonging to the nervous system, as well as in initiating the release of hormones by nervous commands (cf. Gersch, 1964, 1969; Highnam and Hill, 1969). Neurosecretory cells, therefore, are believed to be a link between nervous and endocrine elements (Scharrer, 1970; Scharrer and Weitzman, 1971) and were found to possess both neuronal and endocrine properties (cf. Cook and Milligan, 1972).

It appears, however, that nervous systems in general are concerned with controlling rapid changes by using distinct connections between their elements. On the other hand, endocrine systems regulate slow and often long-lasting changes associated with development and metabolism. In cooperative fashion, both systems determine the responsiveness of animals equally to external and internal stimuli during their life cycle. One example may illustrate this cooperation: stridulation and courtship behavior in male and female grasshoppers, Gomphocerippus rufus L., are based upon the integration of visual, auditory, and tactile sensory inputs by neurons in the brain (Huber, 1955a, 1964), and are organized by neurons located in the ventral nerve cord which altogether determine the duration and the spatial–temporal pattern of courtship events (Eisner, 1968, 1971; Elsner and Huber, 1973). Females sing only at certain times during their reproductive period and mainly in response to acoustical stimuli of conspecific males, whereas males sing at any time during their imaginal life (Loher and Huber, 1964, 1966). It has been shown that singing activity of adult females gradually disappears as soon as both corpora allata have been removed, or when the neurosecretory system in the brain has been destroyed, and it gradually returns after active corpora allata were reim-planted into allatectomized females (Loher, 1962, 1966).

II Levels and Principles of Neural Integration

This section deals with some of the aspects of integrative activity taking place in insect nervous systems, and we are particularly concerned with some of the functions of its central part in the control of behavioral activities. This subject has also partly been reviewed by Wilson (1966a, 1968a), Hoyle (1964, 1970), Miller (1967), Boistel (1968), and in the two monumental volumes of Bullock and Horridge (1965), as well as in the most delightful book of Roeder (1963, 1967).

All insect nervous systems consist of a chain of central ganglia connected with sensory organs and effector systems via afferent and efferent nerves. Information moves to and from the central nervous system (CNS) via nerve fibers in a coded form, the spatial–temporal pattern of all-or-none nerve impulses called the spikes. The message carried in the different channels can only be varied by changing the interspike intervals in individual nerve fibers.

The important step in neural integration is decoding of the incoming message as well as recoding outgoing commands which give rise both to overt behavioral responses and to less obvious internal regulative changes. However, the output of a nerve cell must not depend entirely upon its input; the output is some function of the input and of intrinsic properties of neurons which determine excitability level and firing threshold (Bullock, 1957, 1962; Bullock and Horridge, 1965).

Neural integration occurs at different levels within the insect nervous system, i.e., at the molecular level (not being considered here), at the cellular or neuronal level, and at the multicellular or system level. As far as the neural basis of insect behavior is concerned, real progress will come from studying the input–output relations of single neurons in quantitative terms, i.e., by analyzing the transfer functions in neuronal circuits, and by determining ...

Table of contents

• Cover image
• Title page
• Table of Contents
• CONTRIBUTORS
• Copyright
• LIST OF CONTRIBUTORS
• PREFACE
• PREFACE TO FIRST EDITION
• CONTENTS OF OTHER VOLUMES
• The Insect and the Internal Environment—Homeostasis—I
• AUTHOR INDEX
• SUBJECT INDEX