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The Endocrine System

The Endocrine System. “Hormone”. The word “hormone” comes from the Greek “ hormon ” which means to “set in motion”. Endo = within Krinein = separate (but it is connected to the nervous system). Nervous vs Endocrine .

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The Endocrine System

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  1. The Endocrine System

  2. “Hormone” The word “hormone” comes from the Greek “hormon” which means to “set in motion”. Endo = within Krinein = separate (but it is connected to the nervous system)

  3. Nervous vs Endocrine • The nervous system exerts point-to-point control through nerves, similar to sending messages by conventional telephone. Nervous control is electrical in nature and fast. • The endocrine system broadcasts its hormonal messages to essentially all cells by secretion into blood and extracellular fluid. Like a radio broadcast, it requires a receiver to get the message - in the case of endocrine messages, cells must bear a receptor for the hormone being broadcast in order to respond.

  4. Endocrine… The endocrine system is composed of cells, tissues, and organs that secrete hormones into body fluids. This action is in contrast to the exocrine system which secretes products into tubes or ducts leading to internal or external structures.

  5. Hormones… 1. are secreted by the endocrine glands and are the body’s internal chemical messengers. • are slow to act and can have long lasting effects.

  6. Hormones… 3. control body functions and influence many behaviors. 4. bind to receptors or diffuse through cell membrane and activate target cells.

  7. Hormone Control The majority of hormones are controlled by negative feedback loops.

  8. Hormone Relationships 1. Opposing: hormones work opposite of each other. EX: insulin decreases blood glucose while glucagon increases blood glucose.

  9. Hormone Relationships • Synergistic: two or more hormones must work together to trigger a target cell. EX: Mammary glands will not produce milk without oxytocinprolactin, progesterone, and estrogen

  10. Hormone Relationships • Permissive: one hormone can not be effective until a different hormone “primes” the target cell. EX: Before a female becomes pregnant, her uterus has to been exposed to estrogen followed by progesterone.

  11. Major Hormone Types • Steroids: are derived from cholesterol • Nonsteroidal or amines: are derived from amino acids. (Some researchers divide hormones into four functional groups.)

  12. Steroids: Four covalently bonded rings with differing side chains. EX: Adrenal cortex Gonads

  13. Peptides: Largest number of hormones: Hypothalamus Ant & Pos. Pituitary Islets of Langerhans Parathyroid hormone Digestive system hormones

  14. Steroid Hormones Examples: cortisol, aldosterone, and the sex hormones – estrogens and androgens Lipid soluble – not water soluble. Can diffuse across the cell membrane or bind to a receptor.

  15. Steroid Hormones Examples: Stanozolol – increases muscle proteins over a short period of time. Negative effects – stunted growth, early hair loss, in males – breast development and in females – deeper voices. Serious side effects – liver, kidney, or heart damage..

  16. Hormone Actions Both types of hormones work by altering metabolic processes after binding to specific receptors – the specific steps differ between the two types.

  17. Steroid Steps • The hormone is secreted. • It enter the cell through diffusion. • It combines with a receptor molecule.

  18. Steroid Steps • The complex binds to DNA and promotes transcription. • mRNA enters the cytoplasm and directs translation. 6. Proteins then produce the hormone’s special effects.

  19. Mechanisms of Hormone Action Lipid-soluble steroids & thyroid hormones Diffuse Enter nucleus Forms “hormone-receptor complex” H-R complex binds as transcription factors to chromosome to activate/inactivate gene(s)

  20. Amine Hormones Examples: epinepherine, norepinepherine, and stimulating hormones. Water soluble – not lipid soluble. Cannot diffuse across the cell membrane so it binds to a receptor.

  21. Amine Steps • The hormone is secreted. • It binds to membrane receptor (1st messenger) and activates the G protein. • G protein activates in turn activates adenylatecyclase.

  22. Amine Steps • Adenylatecyclase converts ATP to cyclic AMP (cAMP which is the 2nd messenger). • cAMP activates kinase. • Metabolic processes are altered. • Hormone effects are seen.

  23. Mechanisms of Hormone Action Peptides & water-soluble amines Hormone binds to receptor on cell surface Activates G- protein Activates adenylatecyclase which converts ATP to cAMP cAMP activates protein kinases, which produce final effect.

  24. Hormone Targets

  25. Receptor Target cell concept Target cell Hormone

  26. Not all hormonesfind their target How are chemical signals sent to cells?

  27. Hormone Influences Three major sources: • Other hormones • Nervous system 3. Changes in internal environment

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