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Unformatted text preview: 1 Endocrine System Endocrine System Chapter 12 Chapter 12 Endocrine System Endocrine System Second major controlling system of the body Works closely with the NS NS uses both chemical & electrical stimuli to control rapid actions for short durations NS can stimulate or inhibit the release of hormones Endocrine system uses only chemical stimuli (hormones) Slower than NS but with widespread long-term effects hormones may stimulate or inhibit the generation of nerve impulses Hormones Hormones Regulatory chemicals produced by specialized cells Endocrine glands secrete hormones directly into the bloodstream Hormones may affect many tissues, e.g. growth hormone (GH), insulin, thyroid hormone (TH); or may be tissue- specific, e.g. thyroid stimulating hormone(TSH) Functions of Hormones Functions of Hormones Reproduction Growth and development Mobilization of body defenses Homeostasis Regulation of Metabolism Types of Hormones Types of Hormones Non-steroidal hormones From amino acids Fast acting & short lived Make up most hormones e.g. insulin, growth hormone Steroidal Hormones From lipids Slow acting & long lasting Produced by the adrenal glands & sex glands Can be recognized by the suffix “ -one ” e.g. cortisol, aldosterone, testosterone, estrogen Action & Effects of Hormones Action & Effects of Hormones Non-steroidal hormones Bind to a cell membrane receptor protein The binding sets off a series of chemical reactions 2nd messenger promotes the specific required response Steroidal hormones Bind to a receptor inside the cell’s nucleus Activates genes to synthesize new proteins for cellular functions 2 Mechanism of Hormonal Action Mechanism of Hormonal Action Target cells must have specific protein receptors on the cell membrane for non-steroidal hormones inside the nucleus for steroidal hormones Hormone binding influences the working of the cell via: Changes in the plasma membrane permeability Changes in metabolic reactions Synthesis of proteins & enzymes Activation or inactivation of enzymes Stimulation of mitosis Control of Endocrine Glands Control of Endocrine Glands By other hormones By changing blood levels of certain ions By nerve impulses Hormone Regulation Hormone Regulation Negative Feedback Release of an initial hormone stimulates the release of other hormones which inhibit the release of the initial hormone Most hormones are regulated by negative feedback Positive Feedback Release of an initial hormone stimulates the release of other hormones which stimulate further release of the initial hormone Endocrine Organs Endocrine Organs Pituitary Gland (Hypophysis) Pituitary Gland (Hypophysis) Size of a pea, at the base of the brain Hangs from the hypothalamus by a stalk, the infundibulum Protected by the sphenoid bone The “ Master Gland ” 2 functional lobes...
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This note was uploaded on 09/22/2008 for the course HP 320 taught by Professor Islam during the Spring '08 term at USC.
- Spring '08