Pancreas Flashcards
what does the feeding centre promote?
feelings of hunger and a drive to eat
what does the satiety centre promote?
feelings of fullness (by suppressing the feeding centre)
describe the glycostatic theory controlling the energy intake
food intake is determined by the blood glucose. as it increases the drive to eat decreases.
describe the lipostatic theory controlling energy intake
food intake is determined by fat stores. as fat stores increase the drive to eat decreases.
what is leptin?
a peptide hormone released by fat stores to depress feeding centres
what are the three categories of energy output?
> cellular work
mechanical growth
heat loss
what is metabolism?
integration of all biochemical reactions in the body
what is the net effect in anabolic pathways?
synthesis of large molecules from smaller ones usually for storage purposes
what is the absorptive state?
the state we enter after eating a meal where digested nutrients supply the energy needs of the body and excess is stored
what is the net effect in catabolic pathways?
there is breakdown of large molecules into smaller ones, releasing energy for work
what is the post-absorptive state?
where we really on body stores to provide energy as the nutrients in the plasma decrease.
what is glycogenolysis?
making glucose from glycogen
what is gluconeogenesis?
making glucose from amino acids
what is glycogenesis?
making glycogen from glucose
what is the normal range for glucose?
4.2-6.3mM
name the 4 cell types in the islets of Langerhans
> alpha cells
beta cells
delta cells
F cells
what do alpha cells produce?
glucagon
what do beta cells produce?
insulin
what do delta cells produce?
somatostatin
what do f cells produce?
pancreatic polypeptide (help nutrient absorption from GI)
where is preproinsulin converted to proinsulin?
in the rough endoplasmic reticulum in beta cells
what is proinsulin split into?
> insulin
> c peptide
what is the effect of insulin on excess glucose stored?
> as glycogen in the liver and muscles
> as triacylglycerols in the liver and adipose
what is the effect of insulin secretion on amino acids?
they are made into new proteins and the excess is converted to fat
what is the effect of insulin secretion on fatty acids?
they are stored in the form of triglycerides in the adipose tissue and liver
what triggers insulin secretion?
high glucose levels in the blood
how is metabolism affected by insulin?
it is increased
describe how glucose causes insulin secretion
> glucose enters the cell through a GLUT transporter
it increases cellular ATP
this ATP causes the cell to depolarise
this opens Ca2+ channels which acts as an intracellular signal
this triggers exocytosis and secretion of insulin
describe the action of insulin on a cell
> insulin binds to a tyrosine kinase receptor
signal transduction cascade mobilises GLUT4 which migrates to the membrane
glucose is transported into the cell
what happens to GLUT4 transporters when insulin stimulation stops?
they return to the cytoplasmic pool
what receptor does insulin bind to?
tyrosine kinase receptor
what cells are sensitive to insulin?
muscle and fat cells
what transporters are involved in non-insulin dependent glucose uptake?
GLUT 1, 3 and 2
what are glut 1 and 3 transporters used for?
basal glucose uptake in tissues like the brain, kidney and RBC
what cells take up glucose via GLUT 2?
> beta cells of the pancreas
> liver cells
how does insulin indirectly alter glucose transport?
insulin activates hexokinase which lowers intracellular glucose concentration creating a gradient that moves glucose into cells.
what hormone is insulin permissive to?
growth hormone
what is the effect of insulin of potassium ion entry to the cell?
insulin stimulates Na/K ATPase allowing potassium to enter the cell.
what stimulates insulin release?
> vagal nerve activity > increased amino acids > increased blood glucose concentration > glucagon > incretin hormones controlling GI secretion and motility
what inhibits insulin release?
> low [BG]
somatostatin
sympathetic alpha2 effects
stress (hypoxia)
is IV glucose load more or less than the equivalent amount of glucose given orally?
it is less:
oral glucose increases insulin by direct effect on beta cells AND vagal stimulation of beta cells AND incretin effects
what are the effects of glucagon?
increased:
> gycogenolysis
> gluconeogenesis
> ketogenesis
what cells produce glucagon?
alpha cells
at what blood glucose level will secretion of glucagon increase dramatically?
<5.6mM
what stimulates glucagon secretion?
> stress > cortisol > low [BG] > high [amino acid] > sympathetic innervation (epinephrine)
what inhibits glucagon release?
> glucose > free fatty acids > ketones > insulin > somatostatin
what cells in the pancreas produce somatostatin?
D cells
what is the main pancreatic function of somatostatin?
inhibition of activity in the GI tract: slowing down absorption of nutrients to prevent exaggerated peaks in plasma concentration
what is the effect of somatostatin on insulin and glucagon?
it supresses the release of these hormones in a paracrine fashion
what is the effect of exercise on insulin sensitivity?
it increases sensitivity
true or false:
in type 2 diabetes there can be hyperinsulineamia
true: beta cells ca remain intact so will continue to produce lots of insulin to try and over come the desensitisation of peripheral tissues
does a glucose tolerance test distinguish between type 1 an 2 diabetes?
no it doesn’t
