Endocrine System

• Regulation   * Why are hormones needed?     * Chemical messages from one body part to another     * Communication needed to coordinate whole body     * Daily homeostasis and regulation of large scale changes       * Solute levels in blood         * Glucose         * Ca2+         * Salts       * Metabolism       * Growth       * Development       * Maturation       * Reproduction
• Regulation and Communication   * Animals rely on 2 systems for regulation     * Endocrine system       * System on ductless glands         * Secrete chemical signals directly into blood         * Chemical travels to target tissue         * Target cells have receptor proteins         * Slow, long-lasting response     * Nervous system       * System of neurons         * Transmits “electrical” signal and release neurotransmitters to target tissue         * Fast, short-lasting response
• Regulation by chemical messengers   * Neurotransmitters released by neurons   * Hormones release by endocrine glands
• Classes of Hormones   * Protein based hormones     * Polypeptides       * Small proteins         * Insulin         * ADH     * Glycoproteins       * Large proteins and carbohydrates         * FSH         * LH     * Amines       * Modified amino acids         * Epinephrine         * Melatonin   * Lipid based hormones     * Steroids       * Modified cholesterol         * Sex hormones         * Aldosterone
• How do hormones act on target cells   * Lipid based hormones     * Hydrophobic and lipid-soluble       * Diffuse across cell membrane and enter cells       * Bind to receptor proteins in cytoplasm and nucleus       * Bind to DNA as transcription factors         * Turn on genes   * Protein based hormones     * Hydrophilic and not lipid soluble       * Can’t diffuse across cell membrane       * Bind to receptor proteins in cell membrane       * Trigger secondary messenger pathway       * Activate internal cellular response         * Enzyme action, uptake or secretion of molecules
• Nervous and Endocrine Systems Linked   * Hypothalamus = master nerve control center     * Nervous system     * Receives information from nerves around body about internal conditions     * Releasing hormones       * Regulates release of hormones from pituitary gland   * Pituitary gland = master gland     * Endocrine system     * Secretes broad range of “tropic” hormones regulating other glands in body
• Regulating Metabolism   * Hypothalamus     * TRH       * TSH - releasing hormone   * Anterior Pituitary     * TSH       * Thyroid-stimulating hormone   * Thyroid     * Produces thyroxine hormones     * Metabolism and development       * Bone growth       * Mental development       * Metabolic use of energy       * Blood pressure and heart rate       * Muscle tone       * Digestion       * Reproduction
• Goiter   * Iodine deficiency causes the thyroid to enlarge as it tries to produce thyroxine

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