6C - Control of blood glucose concentration Flashcards
What is the regulation of blood glucose an example of?
The interactions between different hormones in achieving homeostasis.
What are the 2 types of glands?
Exocrine and endocrine.
What do exocrine glands do?
Secrete chemicals outside the body.
What do endocrine glands do?
Communicate using hormones, carried in circulatory system, stimulate target cells with specific receptors.
What type of response do endocrine glands produce?
A slow, long-lasting and widespread response.
What is the endocrine system made of?
- Pituitary gland
- Thyroid and parathyroid gland
- Adrenal glands
- Pancreas
- Ovaries/uterus
- Prostate/testes
What do the thyroid and parathyroid glands release?
Thyroxine
What do the adrenal glands release?
Adrenaline
What do the ovaries/uterus release?
Oestrogen/progesterone
What do the prostate/testes release?
Testosterone
What 3 main effects do hormones have in their target cells?
- Affect the permeability of the cell membrane.
- Cause the release of a ‘second messenger’ inside the cell.
- Diffuse into the cell and promote or inhibit transcription.
Why do we need to control blood glucose?
- Hypoglycemia and hyperglycemia can kill cells due to the effect on water potential of the blood and tissue fluid.
- Required for cellular respiration.
- Required for the manufacture of many other cellular products.
What can change the concentration of glucose in your blood?
Exercise and eating.
What is the normal concentration of glucose in the blood?
Around 90 mg per 100cm^3 of blood.
5 mmol dm^-3
What is blood glucose concentration monitored by?
Cells in the pancreas.
When does blood concentration glucose rise?
After eating food containing carbohydrate.
When does blood glucose concentration fall?
After exercise, as more glucose is used in respiration to release energy.
What 2 hormones control blood glucose concentration?
Insulin and glucagon.
What are insulin and glucagon secreted by?
Clusters of cells in the pancreas called islets of Langerhans.
What makes up the islets of Langerhans?
Alpha and beta cells.
What are the islets of Langerhans?
Group of hormone producing cells, scattered throughout the cells that make digestive enzymes.
What do alpha cells do?
Detect low glucose concentration and secrete glucagon.
What do alpha cells detect?
Low glucose concentration
What do alpha cells secrete?
Glucagon
What is the size of alpha cells like compared to beta cells?
Larger
What do beta cells do?
Detect high glucose concentration and secrete insulin.
What do beta cells detect?
High glucose concentration
What do beta cells secrete?
Insulin
What is the size of beta cells like compared to alpha cells?
Smaller
Which is bigger, alpha or beta cells?
Alpha cells are larger.
What type of cell secretes glucagon?
Alpha cells
What type of cell secretes insulin?
Beta cells
What type of cell detects low glucose concentration?
Alpha cells
What type of cell detects high glucose concentration?
Beta cells
If low glucose concentration is detected, what hormone is secreted?
Glucagon
If high glucose concentration is detected, what hormone is secreted?
Insulin
From what 3 sources does blood glucose come from?
- Directly from the diet.
- Glycogen converted into glucose in the liver (glycogenolysis).
- From gluconeogenesis.
What do changes in supply and demand of glucose allow insulin, glucagon and adrenaline to do?
Operate to maintain a constant blood glucose concentration.
What do insulin and glucagon act on?
Effectors, which respond to restore the blood glucose concentration to the normal level.
What is glycogenesis?
Synthesis of glycogen from glucose.
What is glycogenolysis?
Breakdown of glycogen into glucose.
What is gluconeogenesis?
Synthesis of glucose from lipids, amino acids or nucleic acids.
What is the synthesis of glycogen from glucose called?
Glycogenesis
What is the breakdown of glycogen into glucose called?
Glycogenolysis
What is the synthesis of glucose from lipids, amino acids or nucleic acids called?
Gluconeogenesis
What is glycogenesis activated by?
Insulin
What is glycogenolysis activated by?
Glucagon
What is gluconeogenesis activated by?
Glucagon
What is another name for liver cells?
Hepatocytes.
What does insulin do?
Lowers blood glucose concentration when it’s too high.
What does glucagon do?
Raises blood glucose concentration when it’s too low.
Explain how blood glucose concentration is regulated when it is too high
1) Beta cells in the islets of Langerhans detect it is too high and secrete insulin into the bloodstream.
2) Insulin binds to specific receptors on the cell surface membranes of liver and muscle cells.
3) It increases the permeability of muscle-cell membranes to glucose, so the cells take up more glucose. This involves increasing the number of channel proteins in the cell membrane.
4) Insulin also activates enzymes in the liver and muscle cells that convert glucose into glycogen (glycogenesis).
5) The cells are able to store glycogen in their cytoplasm, as an energy source.
6) Insulin also increases the rate of respiration of glucose, especially in muscle cells.
7) Excess glucose may also undergo conversion to fat.
Where does insulin bind to lower blood glucose concentration?
Cell membrane of liver and muscle cells.
What does insulin do once it has bound to the cell membrane of muscle cells?
It increases the permeability of muscle-cell membranes to glucose, so the cells take up more glucose. This involves increasing the number of channel proteins in the cell membrane.
Insulin also activates enzymes in the liver and muscle cells that convert glucose into glycogen (glycogenesis).
What does insulin do once it has bound to the cell membrane of liver cells?
Insulin activates enzymes in the liver and muscle cells that convert glucose into glycogen (glycogenesis).
What does insulin do to the rate of respiration of glucose?
Increases the rate of respiration of glucose, especially in muscle cells.
What might happen to excess glucose when insulin tries to reduce blood glucose concentration?
It may undergo conversion to fat.
Explain how blood glucose concentration is regulated when it is too low
1) Alpha cells in the islets of Langerhans detect it’s low and secrete glucagon into the bloodstream.
2) Glucagon binds to specific receptors on the cell membranes of liver cells.
3) Glucagon activates enzymes in the liver cells that break down glycogen into glucose (glycogenolysis).
4) Glucagon also activates enzymes that are involved in the formation of glucose from glycerol and amino acids (gluconeogenesis).
5) Glucagon decreases the rate of respiration of glucose in cells.
Where does glucagon bind to raise blood glucose concentration?
Cell membranes of liver cells.
What does glucagon do once it has bound to the cell membrane of liver cells?
- Activates enzymes in the liver cells that break down glycogen into glucose (glycogenolysis).
- Activates enzymes that are involved in the formation of glucose from glycerol and amino acids (gluconeogenesis).
What does glucagon do to the rate of respiration of glucose?
Decreases the rate of respiration of glucose in cells.