19 Nov. 2014 Endocrine-System.ppt 1 Endocrine Systems “Raging Hormones!”
Dec 21, 2015
19 Nov. 2014 Endocrine-System.ppt 2
Human Endocrine System
• Odd organ system• Compare to nervous sys.,
digestive sys.
• Endocrine glands usually not connected• Considered a “system”
because of functional similarity
19 Nov. 2014 Endocrine-System.ppt 3
Endocrine System
• Endocrine glands• Masses of epithelial tissue• Cells secrete into
interstitial spaces,• Secretions (hormones)
diffuse into blood• No ducts!
• Contrast to exocrine glands
19 Nov. 2014 Endocrine-System.ppt 4
Endocrine System
• “Hormone” Chemical messenger
secreted into blood and carried to “target cells” where it alters activity.
Parathyroid hormone (PTH) and calcitonin regulate blood Ca2+
concentration
19 Nov. 2014 Endocrine-System.ppt 5
Endocrine System
• Other chemical messengers• Paracrines
• Autocrines
• Neurotransmitters• discussed in
nervous system
19 Nov. 2014 Endocrine-System.ppt 6
Hormones
• 3-4 Chemical groups• Steroids
• Biogenic amines
• Peptides
• Eicosanoids• Mostly paracrines
• Leukotrienes
• Prostaglandins
19 Nov. 2014 Endocrine-System.ppt 7
Hormones
• Steroids• Derivatives of
cholesterol
• Four covalently-bonded rings
• Adrenal cortex
• Gonads
19 Nov. 2014 Endocrine-System.ppt 8
Hormones
• Biogenic amines• Derivatives of tyrosine,
an amino acidThyroid hormones
• Thyroxine (T4)
• Triiodothyronine (T3)
Adrenal medulla• Epinephrine
• Norepinephrine• Usually
neurotransmitter
19 Nov. 2014 Endocrine-System.ppt 9
Hormones
• Peptides• “Chains” of amino
acids• 4 – 200+ amino acids
• Hypothalamus
• Pituitary (Ant. & Post.)
• Islets of Langerhans
• Parathyroid hormone
• Digestive system hormones
19 Nov. 2014 Endocrine-System.ppt 10
Mechanisms of Hormone Action
• Lipid-soluble steroids & thyroid hormones• Diffuse through plasma
membrane
• Forms “hormone-receptor complex”
• Enter nucleus
• H-R complex binds to chromosome to activate/inactivate gene(s)
19 Nov. 2014 Endocrine-System.ppt 11
Mechanisms of Hormone Action
• Peptides & water-soluble amines• Hormone (1) binds to
receptor on cell surface
• Activates G- protein
• G- protein activates adenylate cyclase
• Converts ATP to cAMP
• cAMP activates protein kinases, which produce final effect.
19 Nov. 2014 Endocrine-System.ppt 12
Hormone Action
• One hormone may have multiple actions • Epinephrine binds to
α and β receptors
• “Fight-or-flight” syndrome
• Activate glycogenolysis
• Dilate arteries to skeletal muscles
• Constrict arteries to viscera
19 Nov. 2014 Endocrine-System.ppt 13
Hormone Action
• Regulation of growth and maturation in insects• PTTH stimulates
prothoracic gland to release ecdysone;
• Ecdysone stimulates formation of new cuticle and molting.
19 Nov. 2014 Endocrine-System.ppt 14
Hormone Action
• Regulation of growth and maturation in insects• Juvenile hormone (JH)
maintains larval development (inhibits maturation);
• JH secretion declines in older larva
pupa adult