Hormonal Control Flashcards
What is endocrine communication?
Specialised glands secrete hormones into the bloodstream.
Circulatory system carries hormone to target cell/ tissue.
Lipid-soluble steroid hormones diffuse into cell and bind to complementary receptor in he cytoplasm. Peptide hormones bind to complementary receptors on the cell surface membrane
Describe the structure of the adrenal glands:
They are located above the kidneys.
They are made up of the adrenal cortex, the adrenal medulla and blood vessels.
The Adrenal Medulla secretes adrenaline in response to danger, stress of excitement as part of the fight or flight response.
The Adrenal Cortex secretes Mineralocorticoids e.g. aldosterone, which targets kidneys and gut to control concentration of sodium and potassium ions in the blood. Also, Glucocorticoids e.g. cortisol and corticosterone, which stimulate an increase in blood glucose concentration.
Why is it important that blood glucose contractions remains stable?
To maintain a constant blood water potential to prevent osmotic lysis and the crenation of cells.
To maintain a constant concentration of respiratory substrates so that the organism maintains constant levels of activity regardless of environmental conditions.
What is negative feedback?
A self-regulatory mechanisms return internal environment to optimum when there is a fluctuation.
Different mechanisms are responsible for dealing with an increase or decrease in normal level for greater control.
What is glycogenesis?
When the liver converts glucose into the storage polymer glycogen
What is Glycogenolysis?
Is when the liver hydrolyses glycogen into glucose which can then diffuse into the blood.
What is Gluconeogenesis?
Is when the liver converts glycerol and amino acids into glucose.
What is the role of glucagon when blood glucose concentration decreases?
- a cells in the Islets of Langerhans in pancreas detect decrease and secrete glucagon into the bloodstream.
- Glucagon binds to surface receptors on the liver cells and activates enzymes for glycogenolysis and gluconeogenesis.
- Glucose diffuses from liver into the bloodstream.
- a cells detect that blood glucose concentration has returned to optimum and to stop producing glucagon by negative feedback.
How does the secondary messenger model explain how Glucose works?
- the hormone-receptor complex forms
- conformational change to receptor activates the G-protein.
- activates adenylate cyclase which converts ATP to cyclic AMP (cAMP).
- cAMP activates protein kinase A pathway
- this results in glycogenolysis
What happens when the blood glucose concentration increases?
- b cells in the Islets of Langerhans in pancreas detect increase and secrete insulin into the bloodstream.
- insulin binds to surface receptors on the target cells to increase the cellular glucose uptake, to activate the enzymes for glycogenesis (in the liver and the muscles) and to stimulate adipose tissue to synthesise fat.
How does insulin lead to a decrease in the blood glucose concentration?
It increases the permeability of cells to glucose.
It increases the glucose concentration gradient.
It triggers inhibition of enzymes for glycogenolysis.
How is insulin secretion controlled?
- b cells have potassium and calcium ion channels to maintain a potential difference -70mV.
- as the glucose concentration increases, glucose enters the b cells via facilitated diffusion.
- Respiration of glucose produces ATP. ATP-gated potassium ion channels close, so potassium ions no longer diffuse out of the cell.
- A potential difference in the cell becomes more positive which equals to depolarisation. Calcium ion channels open so that the calcium triggers exocytosis of insulin.
Describe the exocrine function of the Pancreas?
It secretes digestive enzymes e.g. amylase, trypsin and lipase to the duodenum via the pancreatic tract.
What causes Type 1 diabetes mellitus?
Body cannot produce insulin e.g. due to autoimmune response which attack b cells of the Islets of Langerhans.
How can Type 1 Diabetes Mellitus be controlled?
Treat by injecting insulin from animal source or genetically modified bacteria/ possible future treatment is to use stem cells to produce new b cells.
