The Endocrine System

One way to think of the endocrine system is as another integrating system. By integrating system, I mean a system that helps to organize behavior and physiology. The nervous system is also an integrating system. The endocrine system works at a much slower pace than the nervous system, however. We will consider the endocrine system's mechanism and its effects.

Endocrine or ductless glands are specialized tissues that secrete hormones directly into the bloodstream. Hormones are relatively simple chemicals that are absorbed by other tissues, known as target sites, and used by those tissues.

Examples of endocrine action include physical growth and the menstrual cycle. In humans, physical growth is mediated by a hormone, growth hormone or somatotrophic hormone. It promotes growth from birth to the late teen years. In adulthood, it ceases to work, and growth stops too. During adolescence, growth hormone and the sexual hormones combine to produce the adolescent growth spurt. Such combinations are called synergistic. A synergism is when two or more elements combine and produce greater effects in combination than they do singly. Synergistic effects are also seen when certain drugs are taken in combination.

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