long term processes like

-growth

-development

-reproduction

-Exchange of ions and molecules between adjacent cells across gap junctions

-Occurs between 2 cells of the same type

-Highly specialized and relatively rare

-Uses chemical signals to transfer information from cell to cell within a single tissue

-Most common form of intercellular communication (localized)

-Endocrine cells release chemicals (hormones) into bloodstream

-Alters metabolic activities of many tissues and organs simultaneously

-Affects different cells, goes everywhere

-Stimulate synthesis of enzymes or structural proteins

-Increase or decrease rate of synthesis

-Turn existing enzyme or membrane channel on or off

-Circulate freely or bound to transport proteins (in the bloodstream either way

1. amino acid derivatives

2. peptide hormones

3. lipid derivatives

-Remain functional for less than 1 hour.

1. Diffuse out of bloodstream

-bind to receptors on target cells

2. Are broken down and absorbed by cells of liver of kidney

3. Are broken down by enzymes in plasma or interstitial fluids.

(effect, then done)

-Remain in circulation much longer

-Enter bloodstream

-More than 99% become attached to special transport proteins (survive for a long time. like camoflauge)

-Bloodstream contains substantial reserve of bound hormones

-Thyroid replenishes storehouse in the blood

-protein molecule to which a particular molecule binds strongly

-responds to several different hormones

-different tissues have different combinations of receptors

-presence or absence of specific receptor determines hormonal sensitivity

-receptors modulate what response is

-Catecholamines and peptide hormones

-are not lipid soluble 

-unable to penetrate plasma membrane

-bind to receptor proteins at outer surface of plasma membrane (extracellular receptors)

-cannot have direct effect on activities inside target cell

-use intracellular messengers to exert effects

-functional counterparts of neutral reflexes

-controlled by negative feedback

1. Cyclic-AMP (cAMP)

-derivative of ATP

2. Calcium Ions

-The binding of a small number of hormone molecules to membrane receptors

-Leads to thousands of second messengers in cell (exponential change of what happens inside the cell)

-Magnifies effect of hormone on target cell

-Presence of a hormone triggers decrease in number of hormone receptors

-When levels of particular hormone are high, cells become less sensitive

(diabetes-cells are bombarded with insulin from high glucose intake. Cells become less sensitive to insulin)

-Absence of a hormone triggers increase in number of hormone receptors

-When levels of a particular hormone are low, cells become more sensitive

(menopause uptakes hormone quickly and makes change, over sensitized)

-Activated when hormone binds to receptor at membrane surface and changes concentration of second messenger cAMP within a cell

-increased cAMP level accelerates metabolic activity within cell

1. opening of calcium in channels in membrane

2. release of calcium ions from intracellular stores

3. g protein activates enzyme phospholipase C (PLC)

4. Enzyme triggers receptor cascade

-production of diacylglycerol (DAG) and inositol triphosphate (IP3) from membrane phospholipids

-cAMP works through g protein

Alter rate of dna transcription in nucleus

-change protein synthesis

Directly affect metabolic activity and structure of target cell

Includes steroids and thyroid hormones

(testosterone)