Ch12 Endocrine System

Ch12 Endocrine System - Endocrine System Second major...

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1 Endocrine System Chapter 12 Endocrine System s Second major controlling system of the body s Works closely with the NS s NS uses to control rapid actions for short durations s NS can stimulate or inhibit the release of hormones s Endocrine system uses only chemical stimuli (hormones) s Slower than NS but with widespread long-term effects s hormones may stimulate or inhibit the generation of nerve impulses Hormones s Regulatory chemicals produced by specialized cells s Endocrine glands secrete hormones directly into the bloodstream s 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 s Reproduction s Growth and development s Mobilization of body defenses s Homeostasis s Regulation of Metabolism Types of Hormones Non-steroidal hormones s From amino acids s Fast acting & short lived s Make up most hormones s e.g. insulin, growth hormone Steroidal Hormones s From lipids s s Produced by the adrenal s Can be recognized by the suffix “ -one s e.g. cortisol, aldosterone, testosterone, estrogen Non-steroidal hormones s Bind to a cell membrane receptor protein s The binding sets off a series of chemical reactions c 2nd messenger c promotes the specific required response Steroidal hormones s Bind to a receptor inside the cell’s nucleus s Activates genes to synthesize new proteins for cellular functions
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2 Mechanism of Hormonal Action s Target cells must have specific protein receptors s on the cell membrane for non-steroidal hormones s inside the nucleus for steroidal hormones s Hormone binding influences the working of the cell via: s Changes in the plasma membrane permeability s Changes in metabolic reactions s s Activation or inactivation of enzymes s Stimulation of mitosis Control of Endocrine Glands s By other hormones s By changing blood levels of certain ions s By nerve impulses Hormone Regulation Negative Feedback s Release of an initial hormone stimulates the release of other hormones which inhibit the release of the initial hormone s Most hormones are regulated by negative feedback Positive Feedback s Release of an initial hormone stimulates the release of other hormones which stimulate further release of the initial hormone Endocrine Organs Pituitary Gland (Hypophysis) s Size of a pea, at the base of the brain s Hangs from the hypothalamus by a stalk, the infundibulum s Protected by the sphenoid bone s The “ Master Gland 2 functional lobes s Anterior pituitary s Posterior pituitary Infundibulum Pituitary Pituitary-Hypothalamus Relationship Hypothalamus Relationship s Anterior pituitary hormonal release is controlled by chemical messengers produced by the hypothalamus s Releasing Hormones (RH) s E.g. growth hormone RH (GHRH) s Inhibiting Hormones (IH) s e.g. growth hormone IH (GHIH) & prolactin IH (PIH)
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Ch12 Endocrine System - Endocrine System Second major...

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