19 Nov. 2014Endocrine-System.ppt1 Endocrine Systems “Raging Hormones!”

19 Nov. 2014 Endocrine-System.ppt 1

Endocrine Systems

“Raging Hormones!”


Human Endocrine System

• Odd organ system• Compare to nervous sys.,

digestive sys.

• Endocrine glands usually not connected• Considered a “system”

because of functional similarity


Endocrine System

• Endocrine glands• Masses of epithelial tissue• Cells secrete into

interstitial spaces,• Secretions (hormones)

diffuse into blood• No ducts!

• Contrast to exocrine glands


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


Endocrine System

• Other chemical messengers• Paracrines

• Autocrines

• Neurotransmitters• discussed in

nervous system


Hormones

• 3-4 Chemical groups• Steroids

• Biogenic amines

• Peptides

• Eicosanoids• Mostly paracrines

• Leukotrienes

• Prostaglandins


Hormones

• Steroids• Derivatives of

cholesterol

• Four covalently-bonded rings

• Adrenal cortex

• Gonads


Hormones

• Biogenic amines• Derivatives of tyrosine,

an amino acidThyroid hormones

• Thyroxine (T4)

• Triiodothyronine (T3)

Adrenal medulla• Epinephrine

• Norepinephrine• Usually

neurotransmitter


Hormones

• Peptides• “Chains” of amino

acids• 4 – 200+ amino acids

• Hypothalamus

• Pituitary (Ant. & Post.)

• Islets of Langerhans

• Parathyroid hormone

• Digestive system hormones


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)


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.


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


Hormone Action

• Regulation of growth and maturation in insects• PTTH stimulates

prothoracic gland to release ecdysone;

• Ecdysone stimulates formation of new cuticle and molting.


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


Human Endocrine System

• Odd organ system• Endocrine glands usually

not connected• More glands and hormones

than we can discuss here.

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19 Nov. 2014Endocrine-System.ppt1 Endocrine Systems “Raging Hormones!”