Exam 6 - EXAM 6 (Semester II) Chapter 47The Endocrine...

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EXAM 6 (Semester II) Chapter 47—The Endocrine System The tissues and organs of the vertebrate body cooperate to maintain homeostasis (constant internal conditions) of the body’s internal environment and to control other body functions, such as reproduction. Homeostasis is achieved thru the actions of many regulatory mechanisms that involve all the organs of the body – 2 systems the nervous system and the endocrine system – are devoted exclusively to the regulation of the body organs Regulation is often accomplished by chemical messengers o Types of Regulatory Molecules Regulatory molecules may function as: neurotransmitters, hormones or organ-specific regulators (Paracrine regulators) A hormone is a regulatory chemical secreted into the blood by an endocrine gland or an organ of the body exhibiting an endocrine function, and carried in the bloodstream Paracrine regulators act in the organ in which they were produced and released Another type of chemical messenger that is released into the environment is called PHEROMONE (also called sex-attracting hormone). These messengers aid in the communication between animals, not in the regulation within an animal o Endocrine Glands and Hormones Endocrine glands secrete molecules called hormones into the blood. Any organ that secretes a hormone into the blood is part of the endocrine system Hormones may be any of a variety of different chemicals. Hormones secreted by the endocrine glands are categorized as polypeptides, glycopeptides, amines and steroids The secretory activity of many endocrine glands is controlled by the nervous system o Paracrine Regulation Paracrine regulators act within organs that produced them Paracrine regulators are numerous, and include cytokines, growth factors, neurotrophins, and prostaglandins Prostaglandins help regulate many system, including the immune, reproductive, digestive, respiratory, circulatory, and urinary systems Lipophilic and polar hormones regulate their target cells by different means o Hormones that enter cells Hormones can be divided into lipophilic (lipid-soluble) and lipophobic (hydrophilic)categories Steroid and thyroid hormones are lipophilic hormones that act by entering target cells and stimulating specific genes Lipophilic hormones pass through the target cell’s plasma membrane and bind to intracellular receptor proteins, thereby regulating target cell genes Page 1 Of 14
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EXAM 6 (Semester II) o Hormones that do not enter cells Lipophobic hormones cannot pass through plasma membranes, and thus use messengers within the target cells, such as cyclic AMP, IP3, and Ca+ +, for mediation That is these Lipophobic (the other polar hormones) hormones act by binding to receptors on the cell surface. Many activate second- messenger molecules within the target cells The hypothalamus controls the secretions of the pituitary gland o The Posterior Pituitary Gland The posterior pituitary receives and releases hormones from the
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This note was uploaded on 09/16/2008 for the course BIOL 1722 taught by Professor Jagdeeswaran during the Spring '08 term at North Texas.

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Exam 6 - EXAM 6 (Semester II) Chapter 47The Endocrine...

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