1. 1. What does endo- mean? 2. What is a hormone? 3. What does the word negative mean? 4. What does the word diffusion mean? 5. What is mitosis? 6. What is an enzyme? 7. What does a mRNA molecule do?

2. The ductless gland system

3.  A variety of organs that help coordinate and direct cellular activity by using hormones.  A hormone is chemical substance that are secreted by cells into the extracellular fluids and regulate the metabolic activity of other cells in the body.  Because hormones are being used and they have to diffuse, the results of the endocrine system are much slower than the nervous system.

4.  Steroids – hormones that are made from cholesterol that includes the sex hormones and adrenal cortex hormones  Amino acid-based molecules – nonsteroidal hormones that are derived from amino acids, which have a amino group (-NH 2 )and a carboxyl group (-COOH). They include proteins, peptides, and amines  Prostaglandins – made from highly active lipids found in the cells’ plasma membranes

5.  Reproduction  Growth and development  Mobilizing body defenses against stressors  Maintaining electrolyte, water, and nutrient balance of the blood  Regulating cellular metabolism and energy balance.

6.  Hormones only affect certain cells or organs that are called target cells or target organs.  They affect the target by altering its cellular activity

7.  Change the permeability or electrical state of the cell membrane  Cause the synthesis of proteins or certain regulatory molecules  Activate or inactivate enzymes  Stimulate mitosis

8. Mechanisms of Hormone Action

9.  The hormone 1.Diffuses through the membrane of the target cell 2.Then it enters the nucleus 3.It binds to a specific receptor protein there 4.Hormone-receptor complex then binds to specific sites on the cell’s DNA 5.This activates certain genes to transcribe mRNA molecules 6.mRNA is translated in the cytoplasm, which results in the synthesis of a new protein

10.  These are unable to enter the cell so, they must bind to receptors on the target cell’s plasma membrane and utilize a second- messenger system

11.  The hormone binds to the membrane receptor  This sets off a series of reactions that activates an enzyme  The enzyme catalyzes a reaction that produces a second messenger molecule (Examples: cyclic adenine monophosphate or cAMP, G proteins, calcium ions)  These molecules start making the changes inside the cell that produce the desired effect.

12.  Negative feedback – a stimulus triggers the release of hormones, but the presence of the hormone inhibits further release of more hormones  Types of stimulus ◦ Hormonal – endocrine organs are stimulated by other hormones ◦ Humoral – endocrine organs are stimulated by changing blood levels of certain ions and nutrients ◦ Neural - endocrine organs are stimulated by nerve fibers