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MC Bio 205 Ch 17
endocrine system
| Question | Answer |
|---|---|
| hormone | a molecule that is released in one part of the body but regulates the activity of cells in other parts of the body | the human body has approx 50 types |
| norepinephrine | an example of a molecule that is released both as a neurotransmitter and as a hormone |
| nervous v. endocrine systems: timing | nervous system: the onset of action and the duration of action can usually be measured in milliseconds | endocrine system: slower; takes seconds, hours, or even days |
| nervous v. endocrine systems: types of targets | nervous system: muscle cells, gland cells, other neurons | endocrine system: cells throughout body |
| exocrine glands | secrete products into ducts + then into cavities, lumina, or outside of body | EX/sudoriferous, sebaceous, mucous, digestive glands |
| endocrine glands | release their products into interstitial fluid, from which they enter blood | EX/pituitary, thyroid, parathyroid, adrenal, pineal glands |
| organs and tissues that contain hormone-secreting cells | EX/hypothalamus, thymus, pancreas, ovaries, testes, kidneys, stomach, liver, heart, adipose tissue, placenta |
| F/hormones | regulation of interstitial fluid, metabolism, contraction of smooth/cardiac MT, glandular secretions, some immune activities | development | repro systems | circadian rhythms |
| hormone receptors | C/specific proteins | target cells manufacture more when hormone is in short supply, fewer when hormone is abundant |
| two broad chemical classes of hormones | water-soluble and lipid-soluble |
| lipid-soluble hormones | bind to receptors within target cells | EX/steroid hormones, thyroid hormones, nitric oxide |
| water-soluble hormones | bind to receptors that protrude from target cell surface | EX/amine hormones, peptide hormones, protein hormones |
| peptide v. protein hormones | peptide hormones consist of 3-49 amino acids | protein hormones consist of 50-200 amino acids |
| amine hormones | S/are synthesized by modifying certain amino acids | always retain an amino group: NH3+ |
| transport proteins | most l-s h molecules travel in blood bound to ----- | L/synthesized in liver | F/make l-s hormones temporarily w-s; retard passage of small hormone molecules through kidney filters, thus slowing rate of h loss; provide ready reserve of h in bloodstream |
| free fraction | the small proportion (0.1 - 10%) of l-s h molecules that have been released by their transport proteins | diffuses out of capillaries, bind to receptors, trigger h responses |
| examples of hormone actions | synthesis of new molecules, changing permeability of the plasma membrane, stimulating transport of substance in/out of target cells, changing metabolic reactions, contraction of smooth/cardiac MT |
| general pattern of lipid-soluble hormone action | enter cell | bind to receptor | h-receptor complex alters cell's gene expression | new mRNA forms, enters cytosol, directs synthesis of a new protein, often an enzyme, on the ribosomes |
| first messenger v. second messenger | when w-s h binds to receptor on outer surface of membrane, it acts as the first messenger | the first messenger then causes production of a second messenger inside the cell | very small #s of first-m molecules can cause large chain reactions |
| general pattern of water-soluble hormone action | first messenger binds to receptor on membrane | binding causes adenylate cyclase to convert ATP into cyclic AMP | cAMP activates several enzymes | activated enzymes catalyze physiological responses |
| 3 broad types of hormone interaction | permissive effect: h action requires recent/simultaneous exposure to a second h | synergistic effect: more than one h produces same action, and combined effects are larger than solo effects | antagonistic effect: one h opposes actions of a second h |
Created by:
dglenn34
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