1 The Endocrine System

2 Endocrine system – the body’s second great controlling system Nervous and Endocrine Regulation Delivery Control Response Duration

3 Review of glands  Exocrine  Endocrine – pituitary, thyroid, parathyroid, adrenal, pineal, thymus, ovaries, testes, pancreas, hypothalamus

4 Hormones  Hormones  Regulate the metabolic function of other cells  Are classified as:  Amino acid-based hormones  Steroids  Eicosanoids  Target Cell

5 How hormones activate cells:  Amino acid based (amine) –  Amines, thyroxine, peptide, and protein hormones  Second messenger mechanism

6  Amino acid (Amine) based 1)Hormone binds 2)The G protein is then activated 3)Activated G protein activates the effector enzyme adenylate cyclase 4)Adenylate cyclase generates cAMP from ATP 5)cAMP activates protein kinases (chemical reactions)

7 Steroid based gonadal and adrenocortical hormones, How hormones work

8 Hormone Mode of Action  Changes in target cells  Alter plasma membrane permeability  Stimulate protein synthesis  Activate or deactivate enzyme systems  Induce secretory activity  Stimulate mitosis Hormone inactivation and removal

9 Target cell receptor specificity  Hormones affect target cells only.  Bind to cell surface or intracellular protein receptors.  Further activation is dependent on 3 other factors: 1)Blood levels 2)Relative number of receptors 3)Affinity of those receptors a)Up-regulation b)Down-regulation

10  Three types of hormone interaction  Permissiveness  Synergism  Antagonism Interactions of Hormones at Target Cells

11 Stimuli – Control of hormone release 1) Humoral 2) Neural 3) Hormonal

12Questions: 17.2 Which system produces a quicker response, the nervous system or the endocrine system? Which system produces a longer-acting response? 17.4 Why would follicle stimulating hormone act on the ovaries but not on the thyroid? 17.6 Where do lipid-soluble hormones bind to their target cells? Where do water soluble hormones bind to their target cells? 17.7 Why is cyclic AMP considered to be a second messenger? 17.8 What factors determine the responsiveness of a target cell to a hormone? 17.9 What are the three influences over hormone secretion? Why are organs such as the kidneys, stomach, heart, and skin considered to be part of the endocrine system?