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CH 16

CH 16. THE ENDOCRINE SYSTEM. Endocrine System Function. Achieve and maintain stability of the internal environment (_____________) Regulation through use of chemical messengers called __________________ Communication Integration Control Can work with nervous system – neuroendocrine system.

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CH 16

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  1. CH 16 THE ENDOCRINE SYSTEM

  2. Endocrine System Function • Achieve and maintain stability of the internal environment (_____________) • Regulation through use of chemical messengers called __________________ • Communication • Integration • Control • Can work with nervous system – neuroendocrine system

  3. Major points of the Endocrine System • Nervous System and Endocrine System work together to control various functions of the body. • A hormone can be released from an endocrine gland which affects behavior through the nervous system. • A few endocrine glands respond to a nervous impulse, which activate the endocrine gland to secrete a hormone which in turn affects an organ, organ system or several body systems. • Most endocrine glands respond to changes in the blood level of their own hormone or the hormone of some other endocrine gland.

  4. Endocrine System vs. Nervous SystemSee Table 16-1, page 485

  5. The endocrine and nervous systems overlap in the brain – the pituitary and hypothalamus. The hypothalamus stimulates the pituitary gland via a nerve, and the pituitary affects the hypothalamus with hormones.

  6. Important Vocabulary • Hormone – word means to excite or set in motion. They are the chemical message (or regulators) • Target organ - Organ specifically affected by the action of a hormone. The target organ must have specific protein receptors for hormones. Can also have target tissues and target cells • Exocrine glands – secrete chemicals locally through ducts and have only local effects. • Endocrine glands – secrete chemicals (hormones) directly into the blood stream. These hormones act as chemical messengers to affect several body systems at once. • Neurosecretory tissue – modified neurons that secrete chemical messengers (hormones) that diffuse into the bloodstream not across a synapse.

  7. General hormone action • Hormones bind to specific receptor on or in a target cell • “lock and key” • Hormone-receptor interaction produces a regulatory change in the target cell • synthesis of new protein • Activation/inactivation of enzymes • Opening or closing specific ion channels

  8. General Hormone Action • Different hormones can work in combination or against each other • Synergism-combinations of hormones have a greater effect on a target cell than the sum of the effects that each hormone would have while acting alone • Permissiveness-small amount of 1 hormone allows a second hormone to have its full effect on a target cell • Antagonism-1 hormone produces the opposite effect of another hormone • “fine tunes” a response

  9. General Hormone Action • Hormones travel to target cells by circulating the blood stream • Endocrine glands will produce more hormones than needed to hit the target cell. • Unused hormones are excreted by the kidneys or broken down.

  10. Hormones • Generally they are classified by their chemical structure. Two categories: • Steroid Hormones • Steroids which are lipid soluble and made from cholesterol • Steroid type hormones produce effects that take hours or even days. • Protein Hormones (Book calls them nonsteriod hormones) • Protein hormones which must interact with receptors (other proteins) embedded the cells plasma membrane. • Protein hormones produce immediate effects. (Remember proteins are peptides made from amino acids!)

  11. Mechanism of stEROID Hormone Action

  12. Typical Steroid Hormone Pathway Hormone Capillary interstitial fluid into cell attach to receptor in cytoplasm nucleus attach to DNA activate gene message to ribosomes protein production

  13. Mechanism of Nonsteroid hormone action

  14. Typical Protein Hormone Pathway Hormone Capillary interstitial fluid receptor on cell surface activates adenylcatalase convert ATP  cyclic AMP activate cytoplasmic enzymes normal cell functions

  15. Ways to regulate hormones • Alter rate of synthesis or release of hormone • Alter receptor number (up or down regulation) • Alter rate of degradation or excretion of hormone • Feedback loops (most are negative) • Many hormones are secreted on a rhythmic basis with periods of varying lengths.  For example, circadian rhythms are 24 hr

  16. Where to go from here…… • Rest of the chapter deals with specific endocrine pathways…. • I suggest your READ! • Need to know GLANDS & HORMONES!!

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