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PinkMonkey Online Study Guide-Biology


23.0 Introduction

The behavior of an animal in its environment to maintain itself depends on the coordination of its organs systems. Without coordination of various organ systems, various physiological processes would work in a haphazard way, without linking together activities. The linking together in time and space of various activities of an animal is called coordination. Coordination is brought about by the nervous system and sense organs, and by means of chemical substances (hormones) secreted by the endocrine glands.

During the course of evolution, nervous systems have become more complex. This is largely because animals have become larger and more mobile, requiring more neurons than a sedentary animal. The most fundamental function of a nervous system is (1) to receive a stimulus (2) transmission of a stimulus to a central "brain", (3) interpretation and analysis of the stimulus and (4) proper response by an effector.

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With the evolution of a complex nervous system and bilateral symmetry, cephalization (formation of a head) has taken place, and the ganglia in the head became large enough to be called a brain, which is the main nervous control center of the body.

The Human Nervous System : The human nervous system is divided into two interrelated parts:

(1) The central nervous system (brain and spinal cord).

(2) The peripheral nervous system (nerves and ganglia).

Divisions of the human nervous system

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Table of Contents

23.0 Introduction
23.1 Central nervous system
23.2 The automatic nervous system
23.3 Receptors and effects
23.4 Reflex action - mechanism of nervous action

Chapter 24


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