Blood Glucose, insulin and glucagon Homeostasis and negative feedback

Blood Glucose Carbohydrates in food Glucose in digestive system Must adhere to ‘Goldilocks’ principle Too much is bad = hyperglycemia Too little is bad = hypoglycemia 70-140 mg glucose per dL blood = ‘just right’ Glucose in blood Glucose in cells Cellular Metabolism (aerobic + anaerobic)

Blood Glucose - Abnormal Hypoglycemia <60-65 mg/dL = hunger; shaky, light-headed; rapid heart rate <40-50 mg/dL = loss of mental function, including confusion and/or erratic behavior; seizures; loss of consciousness Hyperglycemia >180 mg/dL Immediate symptoms = increased thirst; headache; fatigue; frequent urination; blurred vision Long term results = nerve damage; blood vessel damage; slow healing; loss of vision; cardiovascular disease

Blood Glucose - REgulation Blood glucose levels maintained by hormones Hormones = proteins made by endocrine glands Hormones = proteins that effect specific cells away from site of hormone production

Pancreas and blood glucose Pancreas is part of digestive system Exocrine gland produces enzymes to digest proteins, carbohydrates and fats (pancreatic juice) Pancreas is part of endocrine system Endocrine (ductless) gland produces hormones insulin and glucagon from ‘Islets of Langerhans’ cells

Negative feedback and blood glucose blood glucose = insulin production Insulin = blood glucose Insulin responds to high glucose and causes it to decrease (‘negative feedback’) blood glucose = glucagon production glucagon = blood glucose Glucagon responds to low glucose and causes it to increase (‘negative feedback’)

Glucagon and blood glucose Blood glucose is low Glucagon produced in alpha cells of pancreas Glucagon effects liver + muscle cells that store glycogen Cells breakdown glycogen to glucose Glucose released to bloodstream + blood glucose increases Glucagon production is stopped

Insulin and blood glucose Blood glucose is high Insulin produced in beta cells of pancreas Insulin effects liver cells that store glycogen Cells absorb glucose and create glycogen Glucose removed from bloodstream + blood glucose decreases Insulin production is stopped

Blood glucose and homeostasis

Problems with homeostasis – Insulin and diabetes Diabetes is a breakdown in homeostasis that results in abnormal blood sugar levels In U.S., 25.8 million people have diabetes (8.3% of total population) 18.8 million are diagnosed 7.0 million are undiagnosed Care of diabetes and diabetes related conditions costs ~$150 billion each year Two forms of diabetes – Type 1 and Type 2 – different cause/same effect

Problems with homeostasis – Insulin and diabetes Type 1 Diabetes (~5% of all diabetes cases) ‘juvenile diabetes’ Cells that produce insulin are destroyed No insulin = high blood glucose levels No insulin = no stored glycogen Type 2 Diabetes (~95% of all diabetes cases) ‘adult onset diabetes’ Cells in liver and muscle become insensitive to insulin (insulin resistance) Insulin resistance = high blood glucose levels Insulin resistance = no stored glycogen