Hormones are chemical substances produced by endocrine glands that are transported via bloodstream to target organs where they exert effects. There are two main types of glands - endocrine glands that secrete hormones directly into bloodstream, and exocrine glands that secrete substances through ducts. Important endocrine glands include the pituitary, thyroid, adrenal and gonads. Hormone production is controlled by the nervous system, other hormones, and chemical substances. Insulin is a hormone produced by the pancreas that regulates blood glucose levels, and diabetes occurs when insulin production or response is abnormal.

1. Hormones and endocrine glands Chapter 15

2. Hormones Definition Chemical substances produced in minute quantities by an endocrine gland that is transported in the bloodstream to target organ(s) where it exerts its effects Assist nervous system in coordination (synergy) Have powerful effects on the body (must balance production) 2 functions: Exercise control over other glands/muscles Control/coordinate body activities (growth & development)

3. 1. 2. 2 methods of testing hormonal levels in our bodies

4. Endocrine vs exocrine glands Exocrine glands = glands that have ducts to carry away their secretions out of the body Endocrine glands = ductless glands = does not have ducts/tubes to carry away its secretion (hormones pass directly into bloodstream for distribution around the body )

5. Examples Endocrine thyroid gland (thyroxine) Exocrine sweat gland (sweat) Both gonads (testosterone) pancreas (pancreatic juice) Islets of Langerhans (insulin & glucagon)

6. Location of endocrine glands

7. Location of the adrenal gland

8. Control of endocrine glands By nervous system Chemical substances Hormones from other endocrine glands

9. Important pointers: Pituitary gland = “master gland”/”controller” -> secretes a number of hormones -> each controls particular gland activity Some glands do not function until a certain age -> reproductive organs (gonads) Long-term vs short-term hormones -> thyroxine (long-term, permanent effects) -> adrenaline (short-lived effects)

10. Important pointers: Production of hormones must be adequate and balanced -> excessive production of certain hormones may be harmful Hormones are destroyed by the liver and excreted by the kidneys after performing their functions

11. Insulin

12. Islet of Langerhans (in pancreas) produce insulin during increase in blood glucose concentration Effects of insulin: [overall increase in cell glucose utilization] Increased cell membrane permeability to glucose -> increasing rate of glucose uptake by cells Cause increased oxidation of glucose during tissue respiration Causes conversion of EXCESS glucose to glycogen for storage in liver and muscles

13. Effects of lack of secretion Blood glucose conc. rises -> not utilized by cells -> diabetes mellitus Body weakness -> no glycogen reserves -> continuous loss of weight Fat oxidation preferred -> formation of ketones (poisonous) -> excreted in urine ( ketonuria ) -> death may occur

14. Effects of oversecretion Abnormal decrease in blood glucose conc. Shock results Coma and death ensues

15. Diabetes mellitus Body unable to control its blood glucose conc. within safe limits Kidney unable to reabsorb all the glucose Glucose not reabsorbed is excreted in the urine 2 main types: Type 1 Type 2

16. Type 1 diabetes Juvenile/early-onset diabetes (occurs early in life) Due to inability of pancreas to produce sufficient insulin

17. Type 2 diabetes Late-onset diabetes (occurs later in life) Overweight people more prone Due to failure of target cells (e.g. muscle cells) to respond to insulin

19. Treatment Measure blood glucose conc. Test urine regularly Watch diet carefully (not too much carbohydrate intake) Type 1 : Inject insulin into veins daily Ensure supply of sugary foods -> too low (due to too much insulin, exercise too much or eat too little -> coma Type 2 : Watch carbohydrate content in diet Seldom need for insulin jabs