Endocrine System
description
Transcript of Endocrine System
Endocrine-System.ppt 1
Endocrine System
“Raging Hormones!”
Endocrine-System.ppt 2
Endocrine System
•Odd organ system– Compare to nervous sys.,
digestive sys.
•Endocrine glands usually not connected– Considered a “system”
because of functional similarity
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Endocrine System
•Endocrine glands– Masses of epithelial tissue– Cells secrete into
interstitial spaces,– Secretions (hormones)
diffuse into blood– No ducts!
•Contrast to exocrine glands
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Endocrine System
•“Hormone”– Chemical messenger
secreted into blood and carried to “target cells” where it alters activity.
•Other chemical messengers– Autocrines– Paracrines
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Hormones
•3-4 Chemical Types– Steroids– Amines– Peptides– (Eicosanoids)
• Mostly paracrines• Leukotrienes• Prostaglandins
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Hormones
•Steroids– Derivatives of
cholesterol– Four covalently-
bonded rings– Adrenal cortex– Gonads
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Hormones•A
mines– Derivatives of tyrosine,
an amino acid– Thyroid hormones
• Thyroxine (T4)
• Triiodothyronine (T3)
– Adrenal medulla• Epinephrine• Norepinephrine
– Usually neurotransmitter
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Hormones•P
eptides– “Chains” of amino acids
• 4 – 200+ amino acids
– Hypothalamus– Pituitary (Ant. & Post.)– Islets of Langerhans– Parathyroid hormone– Digestive system
hormones
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Mechanisms of Hormone Action
•Lipid-soluble steroids & thyroid hormones– Diffuse through plasma
membrane– Enter nucleus– Forms “hormone-receptor
complex”– H-R complex binds to
chromosome to activate/inactivate gene(s)
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Mechanisms of Hormone Action
•Peptides & water-soluble amines– Hormone (A) binds to
receptor on cell surface– Activates G- protein– Activates adenylate cyclase
• Converts ATP to cAMP– cAMP activates protein
kinases, which produce final effect.
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Mechanisms of Hormone Action
•Peptides & water-soluble amines– Other Hormone (B) binds
to receptor on cell surface– Activates G- protein– Inhibits adenylate cyclase
• Stops ATP to cAMP inhibits final effect of
first hormone