Chapter 14 - Hormonal Communication Flashcards
What is Endocrine Communication?
- Glands secrete hormones into bloodstream
- Circulatory system carries hormone to target cell/tissue
- Lipid-soluble steroid hormones diffuse into cell + bind to complimentary receptor in cytoplasm - Peptide hormones bind to complimentary receptor on cell-surface membrane
Describe the structure of the adrenal glands
- located above kidneys
- has a central medulla, surrounded by an external cortex, surrounded by an outer layer.
What hormone does the medulla secrete?
Adrenaline - responds to stress, danger or excitement as part of fight or flight response.
Which horomes does the cortex secrete?
- Mineralocorticoids - e.g. aldosterone, targets kidney and gut to control conc. of Na+ and K+ in blood.
- Glucocorticoids - e.g. cortisol + corticosterone, stimulates increase in blood glucose concentration.
Why is it important that blood glucose concentration remains stable?
- Maintain healthy blood water potential, to prevent osmotic lysis / crenation of cells.
- Maintain constant concetration of respiratory substrate : organism maintains constant level of activity regardless of environment 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
Liver converts glucose into storage polymer glycogen
Define Glycogenolysis
Liver hydrolyses glycogen into glucose, which diffuses into the blood
Define Gluconeogenesis
Liver converts glycerol + amino acids into glucose
Outline the role of glucagon when blood glucose concentration decreases
- alpha cells in islets of langerhans (pancreas) detect decrease + secrete glucagon into the bloodstream.
- Glucagon binds to surface receptors on liver cells + activates enzymes for glycogenolysis + gluconeogenesis
- Glucose diffuses from liver to bloodstream
- alpha cells detect increased BGC and stop producing glucagon (negative feedback)
What is the secondary messenger model for glucagon?
- Hormone-receptor complex forms
- Conformational changes 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 conc. increases
- B cells in islets of langerhans in pancreas detect + secrete insulin to bloodstream
- Insulin binds to surface receptors on target cells to:
A. increase cellular glucose uptake
B. activates enzymes for glycogenesis
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?
- B cells have K+ + Ca2+ ion channels to maintain potential difference (-70mV)
- As Glucose Conc. increases, glucose enters B cells via facilitated diffusion
- Respiration of glucose produces ATP. ATP-gated K+ channels close, 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 exocrine function of pancreas
Secretes digestive enzymes e.g. amylase, tripase, and lipase to the duodenum via the pancreatic tract.
Explain causes of Type 1 Diabetes
Body cannot produce insulin e.g. due to autoimmune disease which attacks B cells of islets of langerhans
How can type 1 diabetes be controlled
Inject insulin from animal source or genetically modified bacteria - possible future treatment involving stem cells to produce new B cells.
Explain causes of Type 2 Diabetes
Glycoprotein receptors become damaged or become less responsive to insulin.
How can type 2 diabetes be controlled
- Strong correlation w/ poor diet + obesity.
- Treat by controlling diet + exercise regime.
What is the difference between Steroid and non-Steroid hormones?
- Steroid hormones = lipid soluble - forms hormone-receptor complex inside the cell.
- Non-Steroid hormones = lipid insoluble - forms hormone-receptor complex on cell surface. Causes cascade reactions, mediated by secondary messenger chemicals.
What are some differences between the hormonal system and the nervous system?
- Hormonal - hormones, transported via blood, response widespread and slow, slow transmission, long-lasting effect.
- Nervous - nerve impulses, transmission via neurones, response localised and rapid, fast transmission, short-lived effect.
What is the difference between adrenaline and noradrenaline?
(both secreted from adrenal medulla)
- Adrenaline increases heart rate, increases blood glucose concentration. (converts glycogen to glucose in the liver)
- Noradrenaline widens pupils, widens lung air passage, and narrows blood vessels in non-essential areas (higher blood pressure)
What are the 2 main functions of the pancreas?
- Exocrine - produce enzymes + release via a duct in the duodenum
- Endocrine - produce horomes + release into the blood.
What are the main products of the pancreas’s exocrine function?
- Amylase - break down starch into simple sugars e.g. pancreatic amylase
- Proteases - break down proteins into amino acids e.g. trypsin
- Lipases - break down lipids into fatty acids + glycerol - e.g. pancreatic lipase.
What is the difference between the alpha and beta cells in the islets of langerhans
a - produce + secrete glucagon
b - produce + secrete insulin
What is the normal blood glucose concentration?
roughly 90 mgcm^-3
What are ways to increase blood glucose concentration?
- Eat carb-rich foods, or sugary foods.
- Glycogenolysis
- Gluconeogenesis
What are ways to decrease blood glucose concentration?
- Respiration - higher activity = higher demand for glucose = decreased blood glucose
- Glycogenesis
