Endocrine System

Lecture: The Endocrine System


The endocrine system is a chemical control system. It functions in conjunction with the nervous system to control the internal environment (homeostasis).


I. Endocrine Glands


      A. Glands without ducts


          1. Secrete HORMONES ("to set in motion") into the intercellular spaces and they pass directly into the blood and is then distributed to all parts of the body via the circulatory system.


          2. Hormones - chemical secretions of the endocrine glands.
                a. chemical types -
                1). proteins and polypeptides (endodermal origin)
                2). Amines (endodermal origin)
                3). steroid (mesodermal origin)


          3. Hormones - act to maintain homeostasis by altering cellular activity.
          4. Hormones can affect


                a.   organ or groups of organs directly ("target organ(s)")
                b. other endocrine glands called "target glands"
                [these hormones are called tropic hormones]


      B. Nervous System vs. Endocrine System

                    Nervous System Endocrine System


          Effects rapid & short-lasting slower & longer lasting
          Controls muscles & glands activities of cells:
                                            a. metabolism
                                            b. reproduction
                                            c. stress responses
                                            d. fluid-electrolyte balance
                                            e. acid-base balance
                                            f. energy balance


II. Pituitary Gland - (Hypophysis) [Master Gland]


      A. Location


          1. in Sella Turcica of sphenoid bone
          2. attached to Hypothalamus by a stalk called Infundibulum


      B. Structure


          1. Anterior lobe – [glandular part]...