Hormonal Communication Flashcards
What is the endocrine system?
Specialised glands that secrete hormones into bloodstream
Circulatory system carries hormone to target cell
Describe the structure of the adrenal glands
Located above the kidneys.
Medulla containing blood vessels surrounded by the cortex
What hormone does the medulla secrete?
Adrenaline in response to danger, stress or excitement as part of the fight or flight response
Which hormone does the cortex secrete?
Mineralocorticoids e.g. aldosterone, which targets kidney and gut to control concentration of Na+ and K+ ions in blood
Glucocorticoids e.g. cortisol and corticosterone, which stimulate an increase in blood glucose concentration
Why is it important that blood glucose concentration remains stable?
Maintain constant blood water potential
Maintain constant concentration of respiratory substrate
Define glycogenesis
Liver converts glucose into glycogen
Define Glycogenolysis
Liver hydrolyses glycogen into glucose which can diffuse into blood
Define gluconeogenesis
liver converts glycerol and amino acids into glucose
Outline the role of glucagon when blood glucose concentration decreases
Alpha and beta cells in the Islets of Langerhans in the pancreas detect decrease and alpha cells secrete glucagon into the blood and beta cells decrease secretion of insulin
glucagon binds to the surface receptors of the hepatocytes and activates enzymes for glycogenolysis and gluconeogenesis
glucose diffuses from liver into blood
alpha cells detect that blood glucose concentration has returned to optimum and stop secreting glucagon
How do non-steroid hormones work?
Hormone binds to specific receptors on plasma membrane
A complementry G protein is activated
This activates the enzyme adenyl cyclase
Adenyl cyclase converts ATP to cAMP which is the secondary messenger
cAMP can act directly on another protein, stimulate
transcription of a gene or can initiate a cascade of enzyme controlled reactions
Outline the role of insulin when blood glucose concentration increases
Alpha and beta cells in the Islets of Langerhans in the pancreas detect increase and beta cells secrete insulin into the blood and alpha cells decrease secretion of glucagon
Insulin binds to surface receptors on target cell to:
increase glucose used in respiration
increase permeability of membranes to glucose
Glycogenesis
What are the 2 types of hormones and examples?
Non-steroid - bind to surface receptors
Adrenaline
Insulin
Glucagon
ADH
Steroid - Have direct effect on DNA
Oestrogen
Testosterone
What are the exocrine functions of the pancreas?
Secretes digestive enzymes e.g amylase, trypsin and lipase to the duodenum via the pancreatic duct
What are the endocrine functions of the pancreas?
Hormones are secreted from
the cells in the islets of
Langerhans
alpha cells manufacture and
secrete the hormone
glucagon
beta cells manufacture and
secrete the hormone insulin
These are released directly
into the blood
How is insulin secretion controlled?
Glucose enters β cells via transporter proteins.
ATP causes closure of potassium ion channels.
Increase in potassium ion concentration inside the cell.
The rise in potassium levels leads to depolarisation, opening calcium ion channels.
The calcium ion influx stimulates insulin release through exocytosis.
Features of type 1 diabetes
Result from an autoimmune disease that destroys beta cells in the pancreas
Leads to no insulin being produced so high blood glucose levels
Develops in childhood
Features of type 2 diabetes
Either beta cells don’t produce enough insulin
OR
Body’s cells resist insulin
results in higher blood glucose concentration
develops later in life
associated with obesity
How is type 1 diabetes treated
Regular insulin injections
Insulin pump to provide continuous insulin
Pancreas transplant of healthy islet cells
Careful blood glucose monitoring and balanced diet with insulin dosage
exercise to regulate blood glucose
How is type 2 diabetes treated
Diet control to reduce sugar intake
Regular physical activity
Medication to increase cells sensitivity to
insulin
Medication to increase insulin production in cells
How can stems cells be used to treat diabetes?
Growing stem cells into beta cells
Implanting stem cells into pancreas of patient with type 1 diabetes
