16.3- Hormones and the regulation of blood glucose concentration

What is the pancreas?

A large gland situated in the upper abdomen behind the stomach

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What does the pancreas secrete?

digestive enzymes (protease, amylase and carbohydrase) and hormones (insulin and glucagon)

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What group of cells in the pancreas is associated with the regulation of blood glucose concentration?

Islets of Langerhans

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What do the islets of langerhans secrete from which cells?

alpha cells secrete glucagon and beta cells secrete insulin

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If blood glucose levels are high, which hormone is secreted?

Insulin

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If blood glucose levels are low, which hormone is secreted?

Glucagon

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Which two hormones can stimulate the breakdown of glycogen into glucose?

Adrenaline and glucagon

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What is the second messenger model?

When a hormone affects the inside of a cell without entering it- it has an indirect effect

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How does adrenaline stimulate the breakdown of glycogen to glucose?

- Adrenaline fuses to liver transmembrane protein receptor - It changes shape on the inside of the membrane activating the enzyme adenyl cyclase inside the membrane - Activated adenyl cyclase converts ATP to cyclic AMP - cAMP activates protein -->

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kinase enzyme by changing its shape - Activated protein kinase enzyme catalyses the conversions of glycogen to glucose

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What types of cells make up the liver?

Hepatocytes

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What is the role of the liver?

To regulate blood glucose concentrations even though its the pancreas that secretes the hormones

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What is glycogenesis?

The conversion of glucose to glycogen when blood glucose is higher than normal

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What is glycogenolysis?

The breakdown of glycogen (stored in the liver) to glucose when blood glucose is lower than normal

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What is glyconeogenesis?

The production og glucose from sources other than carbohydrates such as glycerol and amino acids when glycogen supply is exhausted

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What organ is most affected by lack of glucose for respiration?

The brain as it only respires glucose

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What three sources does blood glucose come from directly?

- Diet - Hydrolysis of glycogen in the small intestine - Gluconeogenesis

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Where is glycogen stored?

In the liver and muscle cells

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Why does the set point of glucose levels fluctuate in animals?

Animals don't eat continuously and their diet varies and glucose is used at different rates depending on the activity

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Where does insulin bind to on most cells?

Glycoprotein

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How does insulin causes glucose to leave the bloodstream?

A rise in insulin levels causes vesicles to fuse with the cell surface membrane- the vesicle membrane contains the protein which makes up glucose channels, increasing their number. Binding of insulin changes the tertiary structure of channel to open

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What else does insulin activate?

Enzymes that convert glucose to glycogen and fat

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Give four ways in which blood glucose concentration is therefore lowered

- Increasing the rate of absorption of glucose into cells - Increasing respiratory rates of cells - Increasing the rate of glycogenesis - Increasing the rate of conversion of glucose to fat

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When does the production of insulin cease?

Once the blood glucose levels drop again ack to the optimum point, the lowering of the blood glucose concentration causes beta cells to reduce their secretion on insulin- negative feedback

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To which mechanism is the regulation of blood glucose levels by alpha cells producing glucagon similar to?

The second messenger model

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16.3- Hormones and the regulation of blood glucose concentration

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