Lecture 71 Flashcards
_________ and _________ work together to regulate blood glucose after a meal and during fasting
insulin and glucose
_________ regulates blood glucose, FA, and AA metabolism
liver, adipose tissue, muscle
Pancreatic _________ synthesize hormones
islets of Langerhans
_________ is the major source of insulin inside the cell and makes up 65%
b cells
20 percent of this cell inside the pancreatic cell makes glucagon and most are around the outer rim of islet
a-cells
10 percent of this cell is interspersed b and a cells and it produces somatostatin
delta-cells
somatostain inhibits _________ cells?
a and b cells
endocrine pancreas is _________ percent of pancreatic mass
1-2 percent
some cells around the pancreatic islet release _________ to self regulate
pancreatic polypeptide
Hormones secreted into pancreatic veins and reach the liver via portal vein. The liver can control?
How much hormones from the pancreas reaches periphery
Central core of islet is _________
beta-cells
_________ connect a- cells to each other, B cells to each other and A to B cells
Gap junctions
Blood supply to the pancreas arranged so that venous blood from each cell type _________ other cell types
bathes
Small arteries enter islet core and capillaries are distributed throughout. Coverage at rim to form _________
veins
Islets innervated by adrenergic, cholinergic and _________ neurons.
peptidergic
first hormone isolated from animal sources, first to have structure determined and mechanism of action described
Insulin
Amino acid sequence varies by _________ but certain segments highly conserved within vertebrates
species
Segments of AA: location of disulfide bonds include end of A chain, c-terminal residues of _________
B-chain
_________ two species have the same sequence of insulin
dog and pig
usually injecting insulin of one species into another causes antibody formation- not a huge issue in _________ and _________ injected with insulin from other species
Dogs and cats
peptide hormone with 2 chains
A chain: 21 AA and B chain: 30 AA
_________ peptide hormone is longer and is biologically active
B chain
_________ are the 3 disulfide bridges
2 link A and B chain and 3rd is in A chain
Insuliin synthesis: Synthesized as _________ with four peptides
prehormones
_________ are the four peptides that comes with insulin synthesis?
- Signal peptide bond cut out early
- A+ B chains
- C chain (comeding peptide)
Insulin synthesis: Proinsulin sent to ER, insulin folds and _________ forms
disulfide bridge
Insulin synthesis: Golgi packages into granules, proteases cut
C peptides
Insulin synthesis: Once golgi packages into granules and proteases cut C-peptudes, secretion happens via exocytosis and releases
Insulin and C-peptide together
Insulin metabolize din the liver creates _________ excreted in urine
Disulfide bond and A+ B chains
most important stimulator of insulin secretion is
blood glucose
1st step in insulin regulation: Transport of glucose into B cell by _________ via facilitated diffusion
GLUT 2 transporter
2nd step in insulin regulation: Glucose immediately phosphorylated by _________ and ATP is the product
Glucokinase
2nd step in insulin regulation continued: Phosphorylation starts signaling needed and prevents glucose from
leaving cell
2nd step in insulin regulation: Glucose immediately phosphorylated by glucokinase and ATP is the product. ATP helps regulate _________?
insulin secretions
3rd step in insulin regulation: ATP closed ATP-sensitive K channels _________ does this do?
depolarizes membrane
4th step in insulin secretion: Depolarization opens voltage gated Ca channels- Ca flows into cell increasing _________?
Intracellular Ca
5th step in insulin secretion: increase in Ca causes exocytosis of insulin granules into _________
Venous blood
C-peptide is secreted in _________ amount to insulin
equal
C peptide excreted is unchanged in the urine this means it is a useful tool to check _________?
B cell function
Oral glucose causes greatest insulin response due to “ _________” effect
Incretin
the incretin effect stimulates release of other hormones from SI such as
GIP and GLP-1 (additive effect to increase insulin)
_________ are other substances that can stimulate insulin secretion?
- AA
- ketoacids
- FFA
- K+
- Ca
- GIP
- Ach
- Glucagon
Glucagon increases the release of glucose from stored glycogen. Blood glucose increase so _________
insulin needed
_________ inhibits insulin secretion
- fasting
- exercise
- somatostatin
- leptin
_________ stores insulin in peripheral cells
skeletal muscle and adipose tissue
Insulin receptor is
tyrosine kinase
Insulin receptor (Tyrosine kinase) have two _________ and two _________
Alpha subunits, beta subnitis
The two alpha subunits of the insulin receptor are
extracellular
The two beta subunits of insulin receptor span membrane and have _________ on intracellular side
Tyrosine kinase
Mechanism of action of insulin in peripheral cell 1 : Insulin binds alpha subunits, causes conformational change and activates tyrosine kinase in _________
Beta subunits
Mechanism of action of insulin in peripheral cell 1 : Tyrosine kinase _________ itself after activated B subunits
Phosphorylates
Mechanism of action of insulin in peripheral cell 2: Tyrosine phosphorylates other proteins/enzymes involved in _________ of insulin
Physiological actions
Mechanism of action of insulin in peripheral cell 2 : Tyrosine kinase phosphorylates other protein/enzymes including?
- Phosphatases
- phospholipases
- G proteins
Mechanism of action of insulin in peripheral cell 3 : Insulin receptor complex internalized by target cell to be
degraded, stored or recycled
Mechanism of action of insulin in peripheral cell 3 : Insulin that is upregulated means it is being
recycled
Action of insulin: When nutrients are available insulin makes sure those nutrients are _________
stored
Glucose stored as _________ in muscles and liver
glycogen
FFA stored as
adipose tissue
proetin stored in?
muscles
Insulin directly stimulates glucose uptake into muscles and fat but not _________
liver
Liver is not dependent on insulin to take up _________
glucose
some glucose transporters are _________ in order to work and some are not
insulin-dependent
_________ are the insulin INDEPENDENT transporters
GLUT 1, GLUT 2 and GLUT 3
This insulin independent transporter is found in brain and RBC.
GLUT 1
This insulin independent transporter is found in liver and beta cells of pancreases
GLUT 2
_________ can cause a decrease in insulin secretion causing chronic hyperglycemia
A decrease number of GLUT 2 transporters on B cells
In the _________ insulin helps with phosphorylation of glucose and store it as glycogen
liver
This insulin independent transport is found in the brain only
GLUT 3
_________ are the insulin DEPENDENT transporters
GLUT 4
GLUT 4 is found in fat, muscles and
brain
Transport of glucose in intestines and kidneys IS NOT regulated by insulin but is _________ dependent
Na
_________ is the glucose transport in the intestines that is Na dependent?
GLUT 5
