Physiology, Health & Exercise

1. Physiology, Health & Exercise Lesson 18 Normal BGL Pathology of diabetes mellitus (DM)

2. Normal BGL & Diabetes Includes: • Role of insulin & glucagon • Pancreas & changes in BGL • Non-insulin dependent diabetes mellitus (NIDDM) • Insulin dependent diabetes mellitus (IDDM)

3. Normal Blood Glucose levels • Glucose- source of energy for body • Carbohydrates digested to glucose • Absorbed by blood capillaries in villi • Carried to liver by hepatic portal vein • Then distributed to body cells

4. Normal Blood Glucose levels If too much glucose (hyperglycaemia) in blood: • Why does this happen? • How does the body respond? • BGL monitored by receptors in Islets of Langerhans (pancreas) • Respond by stimulating an enzyme that promotes production of insulin (by b-cells) • Excess glucose stored as glycogen by liver • BGL fall back to normal levels

6. Normal Blood Glucose levels If glucose levels in blood drop (hypoglycaemia): • Why does this happen? • How does the body respond? • BGL monitored by receptors in Islets of Langerhans (pancreas) • Respond by stimulating an enzyme that promotes production of glucagon (by a-cells) • Glycogen converted into glucose by liver • BGL increase back to normal levels

7. Normal Blood Glucose levels Example of homeostasis • What does this mean? • Why is it described as beingnegative feedback?

8. Normal Blood Glucose levels Insulin can affect a number of different cell types, principally: • Skeletal muscle cells • Liver cells • Fat cells

9. Normal Blood Glucose levels • Skeletal muscle cells & fat cells have very low permeability to glucose in absence of insulin • Insulin acts by stimulating the uptake of glucose into muscle cells • Liver cells are quite permeable to glucose, so glucose enters whether or not insulin is present • But insulin still increases uptake of glucose by liver cells & glycogen formation

10. How does insulin act? • Insulin is a protein hormone • Extracellular hydrophilic • Binds to specific insulin receptors in cell membrane of target cell • Activated receptor promotes recruitment of glucose transporters from intracellular pool to cell membrane • glucose transporters increase insulin- mediated uptake of glucose into cell

11. How does insulin act? • When insulin levels decrease, glucose transporters move from cell membrane to intracellular storage pool, where they can be recycled • Under certain circumstances e.g. obesity, number of insulin receptors decreases • Glucose uptake by cell decreases • Leads to insulin resistance

12. How does insulin act?

13. Types of diabetes mellitus (DM) • Two types: • Type 1- Failure of pancreas to produce adequate quantities of insulin IDDM (insulin dependent DM) • Type 2-Failure of tissues to respond to insulin (insulin resistance) NIDDM (non-insulin dependent DM)

14. Type 1 or IDDM • Accounts for 5-10% of diabetes cases • Caused by destruction of some or all b- cells in Islets of Langerhans • Inadequate insulin production • Commonly occurs in childhood • Previously called early-onset or juvenile-onset diabetes

15. Type 2 or NIDDM • Much more common • Accounts for 90-95% of diabetes cases • Previously called late-onset because more common in people over age of 40 • However becoming more common in younger people (and has been diagnosed in people as young as 13!) • More than 80% of people with NIDDM are overweight • Obesity is the greatest risk factor for NIDDM

16. Type 2 or NIDDM cont… • Can produce insulin • Have insulin levels in blood normal or higher than normal • But target cells (especially in liver & skeletal muscles) have become less sensitive to insulin • Insulin resistance • Deficiency of insulin receptors • Cells less able to take up glucose • BGL rise

17. Type 2 or NIDDM cont… • In this case most people develop Insulin resistance before they develop diabetes • Pancreas tries to compensate by producing more insulin • Eventually the b-cells become “worn out” • Insulin production decreases • Causes an increase in BGL