Homeostasis of blood sugar, breathing and blood pressure Chapter 9 Stage 3 Human Biological Science

Keywords Glucose Glycogen Liver Glycogenesis Glycogenolysis Gluconeogenesis Pancreas Islets of Langerhans Insulin Glucagon Pituitary gland ACTH Adrenal glands Cortisol Adrenaline Noradrenaline

Role of the liver We need glucose (from the food we eat) for cellular energy The liver plays a major role in the control of blood glucose levels The body cannot store glucose, so the liver converts it to glycogen for storage When the body needs glucose, glycogen is converted back to glucose for release into the blood

Glycogenesis The process of converting glucose to glycogen is called glycogenesis This process is stimulated by the hormone insulin Glycogen itself cannot be used by cells so it must be converted back to glucose for use

Glycogenolysis Glycogenolysis is the process which converts glycogen back to glucose for use This process occurs mostly between meals This process is stimulated by the hormone glucagon

Role of the pancreas The pancreas contains hormone secreting cells called the islets of Langerhans There are 2 types of: alpha cells and beta cells Alpha cells secrete glucagon Beta cells secrete insulin

Role of the pancreas Insulin from the beta cells causes a decrease in BGL by accelerating: the transport of glucose from the blood into the cells, especially skeletal muscle cells the conversion of glucose into glycogen Insulin can also Stimulate the conversion of glucose into fat in adipose tissue (fat storage tissue) Cause a increase in protein synthesis in some cells

Role of the pancreas Glucagon from the alpha cells causes an increase in BGL by stimulating the process of glycogenolysis in the liver the liver to produce sugar molecules from fats and amino acids, a process called gluconeogenesis

Glycogenesis High blood glucose Beta cells (pancreas) Liver Stimulus Response Effector Receptor Feedback High blood glucose Beta cells (pancreas) Liver Somatic cells Glycogenesis Increased glucose uptake Lipogenesis Reduced level of blood glucose Beta cells Secrete insulin

Glycogenolysis Alpha cells Low blood (pancreas) glucose Stimulus Response Effector Receptor Feedback Low blood glucose Alpha cells (pancreas) Liver Glycogenolysis Increased level of blood glucose Alpha cells Secrete glucagon

Role of the adrenal glands The pituitary gland, adrenal cortex and adrenal medulla also have a role in regulating BGL Pituitary gland secretes adrenocorticotrophic hormone (ACTH) ACTH acts on the adrenal glands. They secrete glucocorticoids (cortisol) which are involved in gluconeogenesis

The adrenal medulla The adrenal medulla synthesis adrenaline and noradrenaline which act to stimulate the breakdown of glycogen in the liver and the release of glucose into the blood

Links http://bcs.whfreeman.com/thelifewire/content/chp50/5002s.swf http://www.brown.edu/Courses/BI0020_Miller/week/10/web-2/4-2-2007_10-21-10/Chapter_41/Present/Animations/41_A02/41_A02s.html http://www.mhhe.com/biosci/genbio/tlw3/eBridge/Chp27/animations/ch27/1_glucose_regulation.swf http://outreach.mcb.harvard.edu/animations/homeostasis10.swf