Control of Blood Glucose and the Endocrine Pancreas Flashcards
What is responsible for the maintenance of constant blood glucose?
Insulin
Where is insulin secreted?
Pancreas
Explain some functions of the liver
Has high capacity to take up glucose and can buffer increases in blood sugar concentration
Is the pancreas endo or excocrine?
Both, but mostly exocrine as it secretes digestive enzymes forming pancreatic juices into the gut
what is an endocrine gland?
secretes its products directly into the blood (e.g. hormones)
what is an exocrine gland?
secrets its products into ducts that lead to the target tissue (e.g. enzymes)
which parts of the pancreas constitute to the endocrine part?
the islets of langerhans
which parts of the pancreas constitute to the exocrine parts?
they all join up to form the pancreatic duct
what percentage of the islet do beta cells contribute to?
60%
what do the beta cells do?
secrete insulin
what do the alpha cells do?
secrete glucagon
what does the orginal transcript of insulin give?
pre-proinuslin
how does pre-proinsulin become proinsulin?
the signal sequence is cleaves off
how does proinsulin become insulin?
Chain C is removed in golgi apparatus
what type of vesicles is insulin packed into?
secretory vesicles
what is the threshold for insulin release?
5 mmol/L of glucose
what happens when blood glucose reaches 5 mmol/L?
anabolic actions of insulin stop and catabolic actions of glucagon take over
what regulates secretion of insulin?
mostly local (beta cells) but can be regulated by the sympathetic and parasympathetic mechanism
how do the beta cells know when the blood glucose rises?
beta cell membrane has GLUT 2 transporters so as blood glucose rises, it will diffuse into the cell DOWN gradient. it enters glycolysis and TCA cycle to give ATP. an ATP sensitive K+ channel in the membrane closes the channel = depolarisation so K+ cant diffuse out = more positive. The Depolarisation causes Ca2+ channels to open which act as intracellular messengers causing exocytosis of insulin vesicles
what type of messenger is ATP in the sensitive K+ channel?
Intracellular
what are the effects of insulin on the adipose tissue, skeletal muscle, and cardiac muscle?
glucose uptake and FFA/AA in adipose and muscle
How do the effects of insulin take place?
insulin binds to a receptor
what is the insulin receptor?
tyrosine kinase (inside membrane) gets activated by phosphorylation