BIO 5406 Notes, 1/07/08
 

 

INTRODUCTION TO ENDOCRINOLOGY
 

 

I.  Introduction.

 

     A.  Endocrinology  =  Study of the endocrine glands and their secretions.

 

     B.  Study of the hormonal regulation of animal physiology and behavior.

 

     C.  Focus:  Anatomy, biochemistry, physiology, pharmacology, and pathology
          of different endocrine glands and their secretions
 

 

II.  History.                                                                           [Hadley, pp. 2-3]^a

 

     A.  Arnold Berthold, German physiologist, performed experiments on the

          sexual characteristics of roosters, published in 1849.

 

          1.  Castrated roosters (Hadley, fig. 1.1^b).

               a.  Small comb and wattles.
               b.  No interest in hens.
               c.  No aggression towards other males.

 

          2.  Removed testes and replaced one into abdomen of the same

               rooster  ───>  

 

 

          3.  Transplant testis from one rooster into a castrated one  ───>
              

 

          4.  Showed that the testes were functional without

 

 

          5.  Conclusion:
 
 

 

 
 

          6.  First experimental evidence for the effect of an endocrine gland.

 

     B.  First hormone discovered in 1902 by William Bayliss and Ernest
           Starling, British physiologists.

 

          1.  Observed that introduction of acid into the intestine stimulated secretion
               of digestive juices by pancreas.

 

          2.  Isolated a section of dog intestine, connected to body only by blood
               vessels.

 

          3.  Placed HCl in the isolated section  ───> 

 

 

          4.  Conclusion:
 
 

 

 
 

          5.  Secretin is a peptide hormone that stimulates bicarbonate secretion by
               the pancreas.

 

          6.  Starling coined the term "hormone".

 

     ^a Hadley, M.E.,and Levine, J.E.  Endocrinology, 6th ed., 2007.

     ^b Copyright restrictions apply to all figures.
 

 

III.  Communication Between Cells.                                            [pp. 18-22]

 

     A.  Hormone (Greek: to excite)  =  Chemical messenger that is synthesized
          by specialized cells, secreted into the blood in small amounts, and acts on
          specific receptors in target organs to regulate cellular functions.

 

     B.  Neural vs. hormonal communication.
 
 
 
 
 
 
 
 
 
 
 

          1.  Neurotransmitter  =  Chemical messenger that is secreted by

               neurons into a synapse between the neuron and its effector.

 

     C.  Work of Stefan Kopec, Polish biologist, on insect physiology (1917).

 

           1.  Is the brain necessary for insect metamorphosis?

 

           2.  Gypsy moth larvae usually pupate about 16 days after their last molt.

 

           3.  Removed brains of gypsy moth larvae 7 days after their last molt  ───>
        

 

          4.  Conclusion:
 
 

 

          5.  Removed subesophageal ganglion (connecting brain to rest of nervous
               system)  ───>

 

 

          6.  Removed brains 10 days after their last molt  ───>

 

 

          7.  Kopec's conclusion:
 
 

 
 

          8.  First description of a neurohormone.

 

     D.  Neurohormone  =  Chemical messenger that is secreted by neurons

           into the blood.

 

          1.  These modified neurons are called neurosecretory cells.

 

          2.  Gave birth to the field of neuroendocrinology.

 

     E.  Classical distinctions between neurotransmitters and hormones are now
           blurred.

 

          1.  Examples.

 

               a.  Cholecystokinin, a GI hormone, is also secreted in the brain as a
                    neurotransmitter.

 

               b.  Dopamine, a neurotransmitter, is secreted into the blood to regulate
                    regulate the secretion of prolactin.

 

          2.  Nobel Laureate, Roger Guillemin, has suggested a broader definition
               of a hormone:  "Any substance released by a cell which acts on another
               cell, near or far..."

 

          3.  Problems with this broad definition:
 
 

 

 

 

 

IV.  Chemical Communication Between Animals.                    [pg. 26]

 

     A.  Pheromone  =  Chemical messenger that is secreted into the

           environment and alters the physiology or behavior of other individuals

           of the same species.

 

     B.  Functions include sex attraction, territory marking, and regulation of the
           menstrual or estrous cycle.

 

     C.  Ex. bombykol is a sex attractant pheromone produced by the female
           silkworm moth (fig. 2.5).

 

 

V.  Survey of the Major Endocrine Glands (figure^c).

 

     A.  Pituitary.

 

     B.  Hypothalamus.

 

     C.  Thyroid gland.

 

     D.  Parathyroid glands.

 

     E.  Adrenal glands.

 

     F.  Pancreas.

 

     G.  Ovaries (female).

 

     H.  Testes (male).

 

     ^c Johnson, M.D.  Human Biology: Concepts and Current Issues, 2nd ed., 2003.