2. Controlling Blood Glucose Concentration

Question 1

what are the factors that increase blood glucose levels?

Answer 1

• hydrolysis of carbohydrates
• glycogen stores in the level
• when substances are converted into glucose

Question 2

what are the factors that decrease blood glucose concentration in the body?

Answer 2

• during exercise
• glycogenesis
• too much alcohol intake

Question 3

outline the system that controls blood-glucose levels

Answer 3

receptors- located in the islets of Langerhans in the pancreas
signals- hormones insulin and glucagon, secreted by the pancreas
effectors- liver, muscle and fat cells are the target cells of hormones

Question 4

define endocrine glands

Answer 4

the glands that secrete hormones without ducts

Question 5

define exocrine glands

Answer 5

secrete hormones through ducts

Question 6

name the endocrine tissue found in the pancreas

Answer 6

islets of Langerhans

Question 7

name the two types of cells within the islets of Langerhans

Answer 7

• a cells
• b cells

Question 8

a- cells secrete ______

Answer 8

glucagon

Question 9

b-cells secrete ________

Answer 9

insulin

Question 10

what is the response of insulin when blood-glucose concentration is too high

Answer 10

1. B-cells detect increase in blood-glucose concentration
2. Glucose moves into B-cells via facilitated diffusion
3. vesicles containing insulin move toward cell-surface membrane where they release insulin to the capillaries
4. insulin binds to specific receptors on the membrane of the target cells (muscle, liver, fat storage)
5. insulin binding stimulates the cells to activate glucose transporter proteins to their surface membrane
6. this increases permeability of the cells to glucose
7. diffusion of glucose increases, which lowers the blood-glucose concentration
8. insulin binds to the receptors on the liver cells
9. this stimulates glycogenesis in the liver and therefore increases uptake of glucose

Question 11

define gluconeogenesis

Answer 11

conversion of non-carbohydrates (glycerol and amino acids) into glucose

Question 12

define glycogenesis

Answer 12

conversion of glucose into glycogen

Question 13

define glycogenolysis

Answer 13

breakdown of glycogen to glucose

Question 14

where do gluconeogenesis, glycogenesis and glycogenolysis take place?

Answer 14

the liver

Question 15

what is the response of glucagon when blood glucose is too low

Answer 15

1. the low blood glucose levels are detected by the a and b cells in the islet of Langerhans
2. b-cells respond by stopping the secretion of insulin, reducing the use of glucose by the liver cells
3. a-cells respond by secreting glucagon, binding to the receptors in the cell surface membranes of the liver cells
4. glucagon binding activates enzymes involved in glycogenolysis and enzymes involved in gluconeogenesis
5. glucose is released from the liver and blood glucose concentration increases