MECHANISMS OF ENDOCRINE PHYSIOLOGY

 I  Endocrine Physiology

            A.  Overview

                        1.  variations:  paracrine and autocrine

            B.  Hormones

                        1.  characteristics

                        2.  control of hormone plasma levels

                                    a.  secretion

                                                1.  triggers:  endocrine, neural, humoral

                                                2.  rates and patterns:  diurnal, cyclic, feedback

                                    b.  inactivation and clearance

                                                1.  target

                                                2.  liver

                                                3.  kidney

                                                            a.  tubular secretion

                        2.  types

                                    a.  derivatives of tyrosine

                                    b.  protein

                                    c.  steroid

                        3.  transport

                                    a.  bound vs. unbound

                                                1.  half-life

                                                2.  reaction time

                                                3.  drug competition for carrier site

            C.  Receptors

                        1.  Target sensitivity

                                    a.  numbers and affinity

                                    b.  external effects

                                    c.  self adjustment

                                                1.  “up-regulation”

                                                2.  “down-regulation”

                        2.  Membrane (surface) receptors

                                    a.  protein hormones                                 

                                    b.  “second messengers”                            

                                    c.  adenylate cyclase system

                                                1.  G-proteins, alpha subunit

                                                2.  adenylate cyclase

                                                3.  cyclic AMP

                                                4.  protein kinase

                                                5.  phosphodiesterase 

                        3.  Intracellular receptors

                                    a.  lipophilic hormones                               

                                                1.  steroids                                   

                                                            a.  cytoplasmic receptor   

                                                            b.  nuclear receptor

                                                2.  thyroid hormones

                                                            a.  nuclear receptor

                        4.  Multiple receptors

                                    a.  synergistic effects

                                    b.  permissive effects

                                    c.  antagonistic effects

 When you are finished studying this material you should be able to

            - compare endocrine and exocrine glands

            - compare endocrine, paracrine and autocrine regulation

            - explain why a hormone only affects certain cells

            - describe the general way a hormone affects a cell

            - list the types of stimuli that trigger hormone secretion and give examples

            - define tropin and give examples

            - compare and contrast diurnal and cyclic hormone release

            - identify sites where hormones are inactivated in the body

            - identify where hormones are cleared from the body

            - explain how the amounts of circulating hormone are regulated 

            - compare the three categories of hormones, their structure, their transport, and  how they attach to their target

            - explain the connection between how a hormone is transported and it's half-life

            - explain the connection between how a hormone is transported and it's availability

            - explain how competition for a specific carrier protein will affect the availability of the hormone

            - discuss the factors which create sensitivity in a target cell

            - list some conditions external to the target cell which can affect sensitivity

            - describe how a target can self-adjust its sensitivity

            - explain the need for a "2nd messenger system"

            - describe the role of adenylate cyclase in the cell membrane

            - identify one common second messenger and  describe its role in the cell

            - state the role of phosphodiesterase and explain the importance of this role 

            - compare the binding of amine and steroid hormones to their target cell

            - contrast synergistic, permissive and antagonistic hormone interactions        

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