THE ENDOCRINE SYSTEM Ch 17, Human Anatomy Sonya Schuh-Huerta, Ph.D.
The Human Endocrine System
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Transcript of The Human Endocrine System
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The Human Endocrine System
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1. What are hormones?
• Hormones are chemicals that regulate cells in the body. They are usually produced in one place but affect cells in another area.
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2. How do hormones travel?
• Hormones are secreted into the blood and the circulatory system carries them to other body organs.
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3. Nontarget vs target hormones?
• Nontarget hormones affect many different types of cells.
• Examples: growth hormone, insulin, epinephrine (adrenalin)
• Target hormones have a target, a specific type of cell that they act upon.
• Examples: parathyroid hormone, gastrin
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4. NS vs Endocrine System
• Nervous system allows the body to adjust very quickly to changes in the environment.
• Endocrine system maintains control over a longer period of time.
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5. Connection between systems?
• The hypothalamus in the brain controls the pituitary gland with nerve impulses.
• The pituitary gland stimulates other glands to produce hormones that affect the nerve activity of the hypothalamus.
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6. Hormones affect all cells?• Hormones do not affect all cells. It depends
on the type of receptors the cell has and the number of them.
• Ex. A cell can have a receptor for hormone A, but not hormone B, A will affect that cell but B wouldn’t.
• Ex. Liver and muscle cells have lots of receptors for insulin; bone cells have few receptors for insulin, insulin has a greater effect on liver and muscle than on bone.
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7. Two types of hormones
• Steroid hormones – made of cholesterol and soluble in fat.
• Examples are sex hormones (estrogen, testosterone) and cortisol
• Protein hormones – made of chains of amino acids and soluble in water.
• Examples are insulin, growth hormone, epinephrine
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8. Action of Steroid Hormones• Hormone diffuses through cell membrane
(because they are soluble in fat) of target cell
• Hormone combines with receptor molecule
• They move into the nucleus and attach to DNA
• DNA activates a gene to produce a specific protein to cause the desired hormonal effect.
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9. Action of Protein Hormones
• Hormone attaches to receptor on cell membrane of target cell (can’t pass through membrane because not fat soluble)
• This causes cyclic AMP to be formed • Cyclic AMP activates enzymes in the
cytoplasm which triggers ribosomes to create a specific protein to cause the desired hormonal effect
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Action of Protein Hormones
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Action of Protein Hormones
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10. Two messenger system
• The action of protein hormones is often referred to as a “two messenger system”.
• The hormone that arrived at the cell is the first messenger.
• The Cyclic AMP within the cell is the second messenger.
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Negative Feedback
• Is a type of control system that regulates hormone production
• Works similar to a thermostat on your furnace
• When the desired change is detected, the original action is inhibited
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Negative Feedback