The Endocrine Pancreas 2 Flashcards
(53 cards)
What class of hormone is glucagon?
Peptide hormone
What is the primary function of glucagon?
- raise blood glucose
- glucose mobilising hormone that mainly acts on the liver
What is the plasma half life of glucagon?
5-10 minutes
Where is glucagon mainly degraded?
In the liver
What system does glucagon form part of, which opposes the actions of insulin?
Glucose counter-regulatory control system
What does the glucose counter regulatory control system consist of?
Glucagon
Epinephrine
Cortisol
Growth hormone
Is glucagon most active in the absorptive or post-absorptive state?
Post-absorptive state
What kind of receptors are glucagon receptors?
G-protein coupled receptors linked with adenylate cyclase/cAMP system
What does the activation of glucagon receptors cause?
- increased glycogenolysis
- increased gluconeogenesis
- ketogenesis (formation of ketones from fatty acids (lipolysis)
What effect does increased blood glucose have on insulin and glucagon?
Increased insulin secretion
Decreased glucagon secretion
Decreased blood glucose has the opposite effects
How do amino acids impact the release of insulin and glucagon?
- stimulates release of both
- an adaptation to adjust for the composition of a meal very high in protein
- if not for this effect on glucagon then the insulin stimulating effects would result in very low [BG]
What is meant by obligatory glucose user?
Endocrine system ensures there is enough glucose circulating to supply the needs of the brain
Other than the brain, what can tissues use when glucose is not available?
Free fatty acids and ketones to produce energy
What are examples of stimuli that promote glucagon release?
- low [BG] : <5mM
- high [amino acid]: prevents hypoglycaemia following insulin response to amino acids
- sympathetic innervation and epinephrine, b2 effect
- cortisol
- stress: eg exercise, infection
What are examples of stimuli that inhibits glucagon release?
- glucose
- free fatty acids (FFA) and ketones
- insulin (fails in diabetes so glucagon levels rise despite high [BG]
- somatostatin
How does parasympathetic activity (vagus nerve) impact Islet cells?
Increases insulin and to a lesser extent increases glucagon, in association with the anticipatory phase of digestion
How does sympathetic activity impact Islet cells?
- promotes glucose mobilisation
- increased glucagon
- increased epinephrine
- inhibition of insulin
all appropriate for fight or flight response
Give a summar of glucose counter regulatory controls for:
muscle glycogenolysis
liver glycogenolysis
gluconeogenesis
inhibition of glucose uptake
lipolysis
protein catabolism
What class of hormone is somatostain?
Peptide hormone
What is somatostatin produced by?
D cells of the pancreas
Hypothalamus
What is somatostatin also known as?
Growth hormone inhibiting hormone (GHIH)
What is the main action of somatostatin?
- inhibit activity in GI tract
- slow down absorption of nutrients
- to prevent exaggerated peaks in plasma concentration
What can synthetic somatostatin (SS) be used for clinically?
To help patients with life-threatening diarrhoea associated with gut or pancreatic tumours
What effect does somatostatin have on insulin and glucose?
- not a counter-regulatory hormone in the control of blood glucose
- strongly suppresses the release of both insulin and glucagon in a paracrine fashion
