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Chapter 13 - Chapter 13 1 Distinguish between an endocrine...

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Chapter 13 1) Distinguish between an endocrine gland and an exocrine gland. A. Endocrine gland – gland that secretes hormones directly into the blood B. Exocrine gland – gland that secretes its products into tubes or ducts that lead to internal or external body surfaces 2) Define the term “hormone”. A. Hormone – substance secreted by an endocrine gland and transported in the blood 1. biochemical messengers 2. Target cell – cell with specific receptors on which a hormone exerts its effects 3) List the five chemical classes of hormones. Identify the precursor molecule and cite examples. A. Amines – type of nitrogen-containing organic compound, including hormones from the adrenal medulla 1. Formed from - amino acids 2. Examples – norepinephrine, epinephrine B. Peptides – composed of two or more amino acids 1. Formed from - amino acids 2. Examples – ADH, OT, TRH, SS, GnRH C. Proteins – nitrogen-containing organic compound composed of bonded amino acid molecules 1. Formed from - amino acids 2. Examples –PTH, GH, PRL D. Glycoproteins – compound composed of a carbohydrate and a protein 1. Formed from – protein and carbohydrate 2. Examples – FSH, LH, TSH E. Steroids – lipids that include complex rings of carbon and hydrogen atoms 1. Formed from - cholesterol 2. Examples –estrogens, testosterone, aldosterone, cortisol 4) Discuss the sequence of events in steroid and nonsteriod hormone actions. A. Sequence of Steroid Hormone Action 1. Endocrine gland secretes steroid hormone. 2. Steroid hormone diffuses through target cell membrane and enters cytoplasm or nucleus. 3. Hormone combines with a receptor molecule in the cytoplasm or nucleus. 4. Steroid hormone-receptor complex binds to DNA and promotes transcription of messenger RNA. 5. Messenger RNA enters the cytoplasm and directs protein synthesis. 6. Newly synthesized proteins produce hormone’s specific effects. ( 1 ) A steroid hormone crosses a cell membrane and ( 2 ) combines with a protein receptor, usually in the nucleus. ( 3 ) The hormone-receptor complex activates transcription of specific messenger RNA (mRNA) molecules from DNA. ( 4 ) The mRNA molecules leave the nucleus and enter the cytoplasm ( 5 ) where they guide synthesis of their encoded proteins. In the bloodstream, most molecules of a particular steroid are bound to proteins. Only the few that are not bound are free to enter cells, as shown here.
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Chapter 13 B. Sequences of Actions of Nonsteroid Hormone Using Cyclic AMP 1. Endocrine gland secretes nonsteroid hormone. 2. Body fluid carries hormone to its target cell. 3. Hormone combines with receptor site on membrane of its target cell, activating G protein. a. G protein – organic compound which activates an enzyme bound to the inner surface of the cell membrane, eliciting a signal 4. Adenylate cyclase molecules are activated in target cell’s membrane a. Adenylate cyclase – enzyme activated when certain hormones bind receptors on cell membrane 5. Adenylate cyclase circularizes ATP into cyclic AMP.
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