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Pancreas

Two cell types to produce: 1. digestive enzymes – exocrine glands (acini) 2. hormones – islets of Langerhans 1 – 2% of pancreas are the islets of Langerhans

Islets of Langerhans Two hormones are produced: 1. insulin – beta (β) cells 2. glucagon – alpha (α) cells blue = cell nuclei green = insulin red = glucagon

Hormone Structure insulin peptide hormone glucagon peptide hormone Insulin and glucagon are referred to as antagonistic hormones.

Glycogen A glucose polymer made up of many glucose subunits “Storage form of glucose” Stored within liver and muscle

Action of Insulin Beta cells of pancreas are stimulated to release insulin into the blood. Insulin Liver takes up glucose and stores it as glycogen. Body cells take up more glucose. Blood glucose level declines to set point; stimulus for insulin release diminishes. STIMULUS: Rising blood glucose level (for instance, after eating a carbohydrate- rich meal) Homeostasis: Blood glucose level (about 90 mg/100 mL) Blood glucose level rises to set point; stimulus for glucagon release diminishes. STIMULUS: Dropping blood glucose level (for instance, after skipping a meal) Alpha cells of pancreas are stimulated to release glucagon into the blood. Liver breaks down glycogen and releases glucose into blood. Glucagon Figure 45.12

Example of Insulin’s Effect on Body Cells - Muscle Cell Insulin Receptors Insulin GLUT 4 Protein Vesicles GLUT 4 Transporters (proteins that transport glucose across plasma membrane) Signal Transduction Pathway Exocytosis Glucose OUTSIDE CELL INSIDE CELL

When is insulin released? after eating hyperglycemia beta cells cellular signals for insulin release decreased blood sugar increased glucose uptake glycogen production in liver

Beta cells of pancreas are stimulated to release insulin into the blood. Insulin Liver takes up glucose and stores it as glycogen. Body cells take up more glucose. Blood glucose level declines to set point; stimulus for insulin release diminishes. STIMULUS: Rising blood glucose level (for instance, after eating a carbohydrate- rich meal) Homeostasis: Blood glucose level (about 90 mg/100 mL) Blood glucose level rises to set point; stimulus for glucagon release diminishes. STIMULUS: Dropping blood glucose level (for instance, after skipping a meal) Alpha cells of pancreas are stimulated to release glucagon into the blood. Liver breaks down glycogen and releases glucose into blood. Glucagon Action of Glucagon

What does glucagon do? breaks down glycogen hypoglycemia alpha cells cellular signals for glucagon release increased blood sugar glucose release from liver glucose production in liver

Diabetes Mellitus – Type I also known as juvenile diabetes or insulin-dependent diabetes Cause immune system attacking insulin- producing beta cells no insulin production Symptoms increased thirst, hunger and urination Treatment daily dosage of insulin

Diabetes Mellitus – Type II also known as adult-onset diabetes or non-insulin-dependent diabetes Cause Poor diet, lack of exercise Excess glucose in the blood for a long period of time causes the pancreas to become overworked and tired Beta cells produce some, but not enough insulin (deficiency) A reduction in the number of functional insulin receptors reduced responsiveness of cells to insulin = insulin resistant Symptoms increased thirst, hunger and urination fatigue / lethargy

Type II Diabetes Treatment maintain healthy diet and frequent exercise medication only upon progression of disease state Regular exercise can reduce and stop symptoms Insulin GLUT 4 Protein Vesicles Exocytosis Exercise GLUT 4 Protein Vesicles Insulin Glucose

Canadian Connection Frederick Banting & Charles Best Nobel Prize – 1923 Insulin isolation tied off ducts to digestive tract cell producing digestive enzymes shrivelled only islets of Langerhans remained

Video Testimonies University of Alberta developed islet cell transplant method Islet Transplant Animation Photo Journal News Feature

Spinal cord (cross section) Nerve signals Nerve cell Releasing hormone Stress Hypothalamus Anterior pituitary Blood vessel ACTH Adrenal gland Kidney Adrenal medulla secretes epinephrine and norepinephrine. Adrenal cortex secretes mineralocorticoids and glucocorticoids. Effects of epinephrine and norepinephrine: 1. Glycogen broken down to glucose; increased blood glucose 2. Increased blood pressure 3. Increased breathing rate 4. Increased metabolic rate 5. Change in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity Effects of mineralocorticoids: 1. Retention of sodium ions and water by kidneys 2. Increased blood volume and blood pressure Effects of glucocorticoids: 1. Proteins and fats broken down and converted to glucose, leading to increased blood glucose 2. Immune system may be suppressed (b) Long-term stress response (a) Short-term stress response Nerve cell Stress Regulation

Classwork/Homework Section 8.2 – Pg. 383 #1-8,9