CHAP18_2402 - BIOLOGY 2402 Anatomy and Physiology Lecture...

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BIOLOGY 2402 Anatomy and Physiology Lecture Chapter 18 THE ENDOCRINE SYSTEM
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COMPARISON OF CONTROL BY THE NERVOUS AND ENDOCRINE SYSTEM Nervous System and Endocrine System are the two major regulatory systems of the body. Together, they regulate and coordinate the activity of essentially all other body structures. Nervous System – Functions something like telephone messages sent along telephone wires to their destination. - It transmits information in the form of action potentials along the axons of nerve cells. - Chemical signals in the form of neurotransmitters are released at synapses between neurons and the cells the control. Endocrine System – Functions more like radio signals broadcast widely that everyone with radios tuned to the proper channel can receive. - It sends information to the cells it controls in the form of chemical signals released from endocrine glands. - The chemical signals are carried to all parts of the body by the circulatory system. - Cells that are able to recognize the chemical signals respond to them and other cells do not. GENERAL CHARACTERISTICS OF THE EDOCRINE SYSTEM Endocrine System is composed of glands that secrete chemical signals into the circulatory system. Hormones are the secretory products of endocrine glands.
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Hormone is a chemical signal, or ligand that: 1. Is produced in minute amounts by collection of cells; 2. Is secreted into the interstitial spaces; 3. Enters the circulatory system, where it is transported some distance; and 4. Acts on specific tissues called target tissues at another site in the body to influence the activity of those tissues in a specific fashion. Intercellular chemical signals – Allow one cell to communicate with other cells. Autocrine chemical signals – Are released by cells and have a local effect on the same cell type from which the chemical signals are released. Paracrine chemical signals – Are released by cells and affect other cell types locally without being transported in the blood. Pheromones – Are chemical signals secreted into the environment that modify the behavior and the physiology of other individuals. CHEMICAL STRUCTURE OF HORMONES Hormones, including neurohormones (chemical signals secreted by neurons into the circulatory system), can be either proteins, short sequence of amino acids called polypeptides, derivatives of amino acids, or lipids. - Some protein hormones, called glycoprotein hormones, are composed of one or more polypeptide chains and carbohydrate molecules. - Lipid hormones are either steroids or derivatives of fatty acids. CONTROL OF SECRETION RATE Most hormones are not secreted at a constant rate. Instead, most endocrine glands increase and decrease their secretory activity dramatically over time.
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Three Major Patterns of Hormone Regulation 1. Involves the action of a substance other than hormone on the endocrine gland. Involves the influence of blood glucose on insulin secretion. 2. Involves neural control of the endocrine gland. Sensory input and emotions
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CHAP18_2402 - BIOLOGY 2402 Anatomy and Physiology Lecture...

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