Pages

 Hormones are chemical messengers  Three classifications:  Two main groups: 1. Amino acid–based:  Proteins  Peptides (chains of amino acids; smaller than proteins)  Amines (a derivative of ammonia) 2. Steroids—made from cholesterol (lipid based)  Local Hormones: 3. Prostaglandins— made from highly active lipids that are released from almost all cell membranes © 2015 Pearson Education, Inc.

 Hormones are specific  Target a cell or organ  Target cells must have specific protein receptors  Hormone binding alters cellular activity  The act of a hormone binding to its target cell is very similar to that of an enzyme and its substrate- like a lock and key mechanism © 2015 Pearson Education, Inc.

Hormones can cause: 1. Changes in membrane permeability or electrical state 2. Synthesis of proteins, such as enzymes 3. Activation or inactivation of enzymes 4. Stimulation of mitosis 5. Promotion of secretory activity © 2015 Pearson Education, Inc.

 The chemical structure of a hormone determines how it is delivered to its target  Two mechanisms: 1. Direct gene activation Steroids Ex: hormones of the adrenal cortex: corticosteroids 2. Indirect delivery: Second-messenger system (a middle man) 1. Water soluble, non-steroids (protein/peptide hormones) © 2015 Pearson Education, Inc.

1. Diffuse directly through cell membrane 2. Enter the nucleus 3. Bind to a receptor protein within the nucleus 4. This hormone-receptor complex binds to specific sites on the cell’s DNA 5. Certain genes are activated to synthesize new proteins 10/animation__mechanism_of_steroid_hormone_action__quiz_1_.html © 2015 Pearson Education, Inc.

Steroid hormone Cytoplasm Nucleus Receptor protein Hormone-receptor complex DNA mRNA New protein Plasma membrane of target cell 1 (a) Steroid hormone action Slide 1

1. Hormone (first messenger) binds to a membrane receptor 2. Activated receptor sets off a series of reactions that activates an enzyme 3. Enzyme catalyzes a reaction to produce a second messenger 4. Second messenger manage additional intracellular changes to promote a specific response in the target cell © 2015 Pearson Education, Inc.

(b) Nonsteroid hormone action Plasma membrane of target cell Receptor protein Nonsteroid hormone (first messenger) Cytoplasm Enzyme ATP cAMP Second messenger Effect on cellular function, such as glycogen breakdown Slide 1

 Three mechanisms for stimulus of glands: 1. Hormonal (most common) Endocrine organs are activated by other hormones Ex: anterior pituitary secretes hormones that stimulate other glands to release hormones 2. Humoral Changing blood levels of certain ions and nutrients stimulate hormone release Ex: PTH/calcitonin released in response to Ca ⁺⁺ levels 3. Neural Nerve impulses stimulate hormone release Ex: sympathetic division stimulates release of epinephrine/norepinehprine by the adrenal medulla © 2015 Pearson Education, Inc.

 Hormonal Communication  chapter20/animation__hormonal_communication.html chapter20/animation__hormonal_communication.html  Hormone function summarized with animation for both chemical types of hormones 