14.3 Regulation Of Blood Glucose Concentration

Question 1

What causes increase in blood glucose conc

Answer 1

-Diet (after eating a carbohydrate rich meal)
- glycogenolysis (glycogen broken down into glucose)
- gluconeogenesis (production of glucose from non-carbohydrate sources e.g. liver is able to make glucose from glycerol and amino acids)

Question 2

What causes decrease in blood glucose conc

Answer 2

• respiration, especially after exercise
• glycogenesis (production of glycogen)

Question 3

Negative feedback mechanism when theres a rise in blood glucose

Answer 3

• pancreas detects rise in blood glucose
• beta cells secrete insulin, and the alpha cells stop secreting glucagon
• insulin binds to receptors on the liver and muscle cells
• glycogenesis is activated (decrease blood glucose), cells take up more glucose
• blood glucose conc falls

Question 4

Negative feedback mechanism of a fall in blood glucose conc

Answer 4

• pancreas detects decrease
• alpha cells release glucagon, beta cells stop secrete insulin
• glucagon binds to receptors on liver cells
• glycogenolysis activated (breakdown of glycogen back into glucose), gluconeogenesis is activated (production of glucose from non carbohydrate sources)

Question 5

Control of insulin by beta cells

Answer 5

When blood glucose conc rises this is detected by beta cells and insulin is released. Mechanism:
1) at normal bgc levels, potassium channels in the plasma membrane of beta cells are open and potassium ions diffuse out of the cells. The inside of the cell is at a potentials of -70mV relative to outside of the cell.
2) when bgc rises., glucose enters the cells by a glucose transporter
3) the glucose is metabolised inside the mitochondria, resulting in the production of ATP
4) the ATP binds to potassium channels causing them to close (as they are atp sensitive potassium channels)
5) as potassium ions can no longer diffuse out of the cell, the potential difference reduces to around -30mv and depolarisation occurs
6) depolarisation causes the voltage gated calcium ion channels to open
7) calcium ions enter the cell and cause secretory vesicles to release insulin they contain by exocytosis