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32 Cards in this Set
- Front
- Back
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Secretes hormone; no ducts
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Endocrine gland
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Chemical messenger, carried in blood, affects target cells
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Hormone
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Cells that have receptors for the hormone
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Target cells
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Binds to hormone, required for response to the hormone
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Receptor
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-Fast response
-Short duration -Secretes neurotransmitters -Specific, localized effects |
Nervous system
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-Slow response
-Longer duration -Secretes hormones -Widespread effects |
Endocrine system
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Classes of Chemical Signal Molecules
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1. Neurotransmitters
2. Hormones 3. Neurohormones 4. Paracrine substances (e.g. prostaglandins) |
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Affect a specific cell (the postsynaptic cell) at a synapse
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Neurotransmitters
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Affect target cells throughout the body
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Hormones
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Hormones secreted by neurons
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Neurohormones
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Exert local effects on neighboring cells
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Paracrine substances
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-E.g. steroid hormones, thyroid hormones, eicosanoids
-Cross the plasma membrane -Bind to intracellular (cytoplasmic) receptors |
Lipophilic (lipid-soluble)
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-E.g. epinephrine, insulin, antidiuretic hormone
-Do not cross the plasma membrane -Bind to receptors on the PM |
Lipophobic (water-soluble)
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-Hormone binds to cytoplasmic receptor
-Intracellular hormone-receptor complex --> binds to DNA, acts as transcription factor -->Regulates increase or decrease transcription of specific genes --> mRNA --> protein synthesis -->Metabolic and developmental effects |
Lipophilic hormones
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-Hormone binds to membrane receptor
-Hormone-receptor binding activates a SIGNAL TRANSDUCTION pathway -->Activates enzymes within the cell -->Mostly metabolic effects |
Lipophobic hormones
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Activation of rapid cellular responses
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Signal transduction pathway
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Insulin receptor - tyrosine kinase
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Enzyme-linked receptors
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Binding of hormone to receptor
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G protein-coupled receptors
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Explain the cyclic AMP second messenger system
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1. Hormone binds to receptor
2. G protein associated with receptor is activated 3. Activated G protein activates ADENYLYL CYCLASE in the plasma membrane 4. Adenylyl cyclase converts ATP to cyclic AMP 5. Cyclic AMP acts as a SECOND MESSENGER, activates PROTEIN KINASE enzymes in the cell 6. Protein kinase activates other enzymes via phosphorylation -->Amplification of cellular response |
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What are the two second mesenger systems?
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1. Cyclic AMP second messenger system
2. Phospholipase-C (DAG-IP3) second messenger system |
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Explain the phosphlipase-C second messenger system
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--G-protein couple receptor
-Activation of G protein activates Phospholipase C enzyme in the cell membrane -Phospholipase C cleaves a membrane phospholipid -Forms 2 second messengers: diacylglycerol (DAG) and inositol triphosphate (IP3) |
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In the phospholipase-C second messenger system, what forms the 2 second messengers
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Diacylglycerol (DAG) and inositol triphosphate (IP3)
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By neurons that synapse on endocrine cells
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Neural
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By substances in the blood or interstitial fluid
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Humoral
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By other hormones
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Hormonal
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Three parts to "Responsiveness to Hormones"
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1. Concentration of hormone in the blood
2. Abundance of receptors 3. Influence of other hormones |
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Period of time to break down
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Half-life
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Increase abundance of receptors
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Up-regulation
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Decrease abundance of receptors
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Down-regulation
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Multiply effect, one can amplify another, for example (epinephrine and glucagon)
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Synergistic effects
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This influential effect involves the THYROID HORMONE
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Permissive effects
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Two hormones that counteract each other
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Antagonistic effects
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