Flashcards in Hormones And The Regulation Of Blood Glucose Deck (21):
What is an example of how different hormones interact in achieving homeostasis?
The regulation of blood glucose
Where are hormones produced?
Hormones are produced by glands that secrete the hormones directly into the blood
How are hormones transported and how do they act on specific cells?
They are carried in the blood plasma to the cells on which they act - known as target cells - which have receptors on their cell surface membranes that are complementary to the hormone
What makes hormones effective?
They are effective in very small quantities, but often have very widespread and long-lasting effects
What mechanism is used by two hormones involved in the regulation of blood glucose?
The second messenger model
What are the three main hormones involved in the regulation of blood glucose?
Adrenaline, insulin and glucagon
Outline the second messenger model
The hormone is the first messenger which binds to specific receptors on the cell surface membrane of target cells to form a hormone-receptor complex that activates an enzyme inside the cell that acts as a second messenger which causes a series of chemical changes that produce the required response
What organ is involved in the regulation of blood glucose and what does it secrete in order to do this?
The pancreas which secretes insulin and glucagon
Describe the concept of the second messenger model in the action of adrenaline in regulating blood sugar
The hormone adrenaline approaches and fuses to the receptor site, and in doing so activates an enzyme inside the membrane which converts ATP to cyclic AMP, which acts as a second messenger that activates other enzymes that, in turn, convert glycogen to glucose
What are the hormone producing cells called?
Islets of langerhans
The cells of the islets of Langerhans are of two types. What are they?
Alpha cells which are larger and produce the hormone glucagon, and beta cells which are smaller and produce the hormone insulin
What is an issue with blood glucose levels rising too high?
It lowers the water potential of the blood and creates osmotic problems that can cause dehydration and be equally dangerous
What are the body's 3 sources of glucose?
Directly from the diet, from the breakdown of glycogen (glycogenesis) stored in the liver and muscle cells and from gluconeogenesis (e.g glucose can be made in the liver from glycerol and amino acids)
When insulin binds with the receptors on the cell surface membranes of body cells, what three changes does it bring about?
It causes a change in the tertiary structure of the glucose transport protein channels to allow more glucose to enter the cells, there is an increase in the number of carrier molecules in the cell surface membrane and enzymes that convert glucose to glycogen and fat are activated
In what four ways can the blood glucose level be lowered?
By increasing the rate of absorption of glucose into the cells, by increasing the respiratory rate of cells, by increasing the rate of conversion of glucose into glycogen (glycogenesis) in the cells of the liver and muscles and by increasing the rate of conversion of glucose to fat
What does the lowering of the blood glucose level cause?
The beta cells reduce their secretion of insulin
How do the alpha cells in the islets of Langerhans respond to a fall in blood glucose?
They secrete glucagon into the blood plasma
How does the glucagon increase blood glucose levels?
It binds to receptors on the liver cells which activates an enzyme that converts glycogen to glucose that increases the conversion of amino acids and glycerol into glucose (glycogenesis)
How do the alpha cells respond to a raising of the blood glucose level?
They reduce their secretion of glucagon
How does adrenaline increase blood glucose levels?
It activates an enzyme that causes the breakdown of glycogen to glucose in the liver and inactivates an enzyme that synthesises glycogen from glucose