Hormonal Communication Flashcards
What is endocrine communication?
Specialised glands secrete hormones into bloodstream. Circulatory system carries hormone to target cell/ tissue.
Lipid-soluble steroid hormones diffuse into cell & bind to complementary receptor in cytoplasm. Peptide hormones bind to complementary receptor on cell-surface membrane.
Describe the structure of the adrenal glands.
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What hormone does the medulla secrete?
Adrenaline in response to danger, stress or excitement as part of the fight or flight response.
Which hormones does the cortex secrete?
● Mineralocorticoids e.g. aldosterone, which targets kidney & gut to control concentration of Na+ & K+ ions in blood.
● Glucocorticoids e.g. cortisol & corticosterone, which stimulate an increase in blood glucose concentration.
Describe the histology of the pancreas
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Why is it important that blood glucose concentration remains stable?
● Maintain constant blood water potential: prevent osmotic lysis/ crenation of cells.
● Maintain constant concentration of respiratory substrate: organism maintains constant level of activity regardless of environmental conditions.
Define negative feedback.
Self-regulatory mechanisms return internal environment to optimum when there is a fluctuation.
Different mechanisms are responsible for dealing with an increase/ decrease in normal level for greater control.
Define glycogenesis, glycogenolysis and gluconeogenesis.
Glycogenesis: liver converts glucose into the storage polymer glycogen.
Glycogenolysis: liver hydrolyses glycogen into glucose which can diffuse into blood.
Gluconeogenesis: liver converts glycerol & amino acids into glucose.
Outline the role of glucagon when blood glucose concentration decreases.
- 𝞪 cells in Islets of Langerhans in pancreas detect decrease & secrete glucagon into bloodstream.
- Glucagon binds to surface receptors on liver cells & activates enzymes for glycogenolysis & gluconeogenesis.
- Glucose diffuses from liver into bloodstream.
- 𝛼 cells detect that blood glucose concentration has returned to
optimum & stop producing glucagon. (negative feedback).
Use the secondary messenger model to explain how glucagon works.
- Hormone-receptor complex forms.
- Conformational change to receptor activates G-protein.
- Activates adenylate cyclase, which converts ATP to
cyclic AMP (cAMP). - cAMP activates protein kinase A pathway.
- Results in glycogenolysis.
Outline what happens when blood glucose concentration increases.
- 𝝱 cells in Islets of Langerhans in pancreas detect increase & secrete insulin into bloodstream.
- Insulin binds to surface receptors on target cells to:
a. increase cellular glucose uptake.
b. activate enzymes for glycogenesis (liver & muscles).
c. stimulate adipose tissue to synthesise fat.
Describe how insulin leads to a decrease in blood glucose concentration.
● Increases permeability of cells to glucose. ● Increases glucose concentration gradient.
● Triggers inhibition of enzymes for glycogenolysis.
How is insulin secretion controlled?
- 𝛽 cells have K+ & Ca2+ ion channels to maintain p.d. -70mV.
- As glucose concentration increases, glucose enters 𝛽 cells via facilitated diffusion.
- Respiration of glucose produces ATP. ATP-gated K+ ion channels close, so K+ ions no longer diffuse out of cell.
- P.d. in cell becomes more positive = depolarisation. Ca2+ ion channels open. Ca2+ triggers exocytosis of insulin
Describe the exocrine function of the pancreas.
Secretes digestive enzymes e.g. amylase, trypsin & lipase to the duodenum via the pancreatic tract.
Explain the causes of Type 1 diabetes mellitus and how it can be controlled.
Body cannot produce insulin e.g. due to autoimmune response which attacks 𝛽 cells of Islets of Langerhans
Treat by injecting insulin from animal source or genetically modified bacteria. Possible future treatment: use stem cells to produce new 𝛽 cells.
