The Endocrine System 1 Endocrine system the bodys

The Endocrine System 1

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

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

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

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

§ 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 c. AMP from ATP 5) c. AMP activates protein kinases (chemical reactions) 6

How hormones work Steroid based gonadal and adrenocortical hormones, 7

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 8

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 9

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

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

Questions: 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? water soluble hormones bind to their target cells? Where do 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 three influences over hormone secretion? Why are organs such as the kidneys, stomach, heart, and skin considered to be part of the endocrine system? 12