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

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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. Links http://bcs.whfreeman.com/thelifewire/content/chp50/5002s.swf