The Endocrine Pancreas 1 Flashcards
what is the Glucostatic theory
food intake is determined by blood glucose: as [BG] increases, the drive to eat decreases
what is the lipostatic theory
food intake is determined by fat stores: as fat stores increase, the drive to eat decreases
what is leptin
Leptin is a peptide hormone released by fat stores which depresses feeding activity.
what is the only part of energy output we can regulate voluntarily
mechanical work done by skeletal muscle
define the term metabolism
integration of all biochemical reactions in the body
what is the absorptive state
After eating we enter an Absorptive State where ingested nutrients supply the energy needs of the body and excess is stored. This is an anabolic phase
what is the post absorptive state
Between meals and overnight the pool of nutrients in the plasma decreases and we enter a Post-absorptive State (aka Fasted State) where we rely on body stores to provide energy. This is a catabolic phase
the body MUST maintain blood glucose concentration [BG] sufficient to meet the brain’s requirements how is this done
BG is maintained by synthesising glucose from glycogen (glycogenolysis) or amino acids (gluconeogensis)
what is the normal range of [BG]
4.2-6.3mM (5mmoles useful to remember)
what [BG] level is considered hypoglycaemia
[BG] < 3mM
where are insulin and glucagon produced
pancreas
the pancreas releases NaHCO3 true or false
true
what percentage of the pancreas has endocrine function
1% the rest operates as an exocrine gland
there are 4 types of ilet cells what are they
alpha, beta, delta and 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
what is the function of pancreatic polypetide
not known, may help control of nutrient absorption from GIT
what type of hormone is insulin
peptide
what is the function of insulin
stimulates glucose uptake by cells
where is preproinsulin converted to proinsulin
in the ER
what is the major stimulus for insulin secretion
blood glucose concentration
what is the only hormone which lowers [BG]
insulin
where is excess glucose stored
stored as glycogen in the liver and muscle. Stored as TAG in liver and adipose tissue
what are amino acids mainly used for
mainly used to make new proteins (excess converted to fat)
what form are fatty acids stored as
triglycerides (TAG) in adipose tissue and liver
B-cells have a specific type of K+ ion channel that is sensitive to the ATP within the cell, what is it called
K ATP channel
what are GLUT’s
glucose transporter proteins
what causes K ATP channels to close
the channels close when glucose enters into the cell and causes an increase in ATP within the cell
what happens when K ATP channels close
intracellular K+ rises, depolarising the cell, voltage dependant ca2+ channels open and trigger insulin vesicle exocytosis into circulation
when are K ATP channels open
when [BG] is low, ATP is low and K ATP channels will be open
why is insulin not secreted when K ATP channels are open
as K+ ions will be flowing out hyperpolarising the cells, so voltage Ca2+ channels remain closed and insulin is not secreted
what receptors does insulin bind to
tyrosine kinase receptors
what are the insulin sensitive tissues
muscle and adipose tissue
insulin stimulates the mobilization of specific glucose transporters, what are they called
GLUT-4
where do GLUT-4 receptors reside
in the cytoplasm of unstimulated muscle and adipose tissue
most types of tissue do NOT require insulin to take up glucose, what 2 tissues requires insulin to take up glucose
muscle and fat
in tissues that don’t require insulin how is glucose taken up into the cell
glucose uptake is via other GLUT-transporters, which are NOT insulin-dependent
where would you find GLUT-2 receptors
Beta cells of pancreas and the liver
what glucose transporters take up glucose into the liver
GLUT 2 (insulin independent)
in the fed state the liver takes up glucose why
glucose moves down the concentration gradient. In the fed state insulin activates hexokinase which lowers glucose concentration in the cell, so glucose moves into the cell.
insulin increases amino acid uptake into muscle promoting protein synthesis true or flase
true, this is one of the additional actions of insulin
what is insulins effect on growth hormone
insulin has a permissive effect on growth hormone
how does insulin promote K+ ion entry into cells
by stimulating Na+/K+ ATPase
what is the half life of insulin
5 mins
where is insulin principally degraded
in the liver and kidneys
once insulin action is complete what happens to insulin bound receptors
they are internalised by endocytosis and destroyed by insulin protease, some recycled
what are the stimuli which increase insulin release
1.increased [BG], 2.increased amino acids, 3.glucagon, hormones controlling GI secretion and motility, vagal nerve activity
what are stimuli which inhibit insulin release
low [BG], somatostatin(GHIH), sympathetic a2 effects, stress e.g hypoxia
