Pancreas and Endocrine Flashcards
Beta cells make up what percent of islet
70%
beta cells secrete
insulin
proinsulin
C peptide
amylin
alpha cells make up what percent of islet
20%
alpha cells secrete
glucagon
delta cells make up what percent of islet
~5%
delta cells secrete
somatostatin
delta cells block
blocks release of insulin and glucagon from nearby cells
blocks release of other gastric hormones and growth hormones
where are beta cells mainly found
middle
where are alpha and delta cells mainly found
periphery
how does blood flow in islet
flows from center outwards
does blood flow deliver somatostatin to beta cells
no
what junctions connect cells to allow for communication and regulation of hormone release in islet of langerhands
tight junctions
gap junctions
parasympathetic stimulation for islet of langerhans
parasympathetic stimulation via vagus nerve
cholinergic to increase insulin –> primes pancreas
sympathetic stimulation for islet of langerhans
alpha adrenergic –> inhibitory
what primes pancreatic beta cells
incretins
definition of incretins
peptides released by intestinal cells that augment beta cell response to oral glucose stimulus
examples of incretins
chyolecystokinin
glucagon-like peptide 1 (GLP-1)
gastric inhibitory polypeptide (GIP)
What is GLP-1 broken down by
dipeptidyl-peptidase 4
where is pre-proinsulin made
rough endoplasmic reticulum
is pre-proinsulin active
no, it is nonactive
order for pre-proinsulin
pre b c a post
biologic activity proinsulin
1% in comparison to insulin
parts of proinsulin
b c a
proinsulin is transported where to create insulin
from RER to golgi apparatus
ratio of insulin to c peptide release into systemic circulation
1:1 ratio
what percent of insulin is removed in first-pass through portal circulation
60%
where is c peptide excreted
in urine
it is not extracted by liver in first pass!!!
function of amylin
inhibits glucagon release
decreases gastric emptying
acts centrally to decrease appetite
what are the two ways that pro glucagon can be processed
alpha cells in the pancreas
neuroendocrine L cells in the intestines
alpha cells in the pancreas create
glucagon
neuroendrocrine L cells create
GLP-1
function of GLP-1
stimulates insulin synthesis and release
glycogenesis
formation of glycogen
glycolysis
metabolic pathway that converts glucose to create energy
glycogenolysis
breakdown of glycogen to glucose
gluconeogenesis
synthesis of new glucose from noncarb precursors
when does glycogenesis occur
when glucose levels are sufficient enough to allow excess glucose to be stored in liver and skeletal muscle
function of glycogenolysis
increases blood glucose levels and provides energy
function of gluconeogesis
provides glucose when dietary intake is insufficient
glucose transport is primarily controlled by
glucose transporters (GLUT)
GLUT allows glucose into the cell via
facilitated diffusion
Where are insulin independent GLUT transporters found
liver
brain
RBC
retina
kidney
nervous tissue
what is the catalyst that converts glucose to G-6-P through phosphorylation
hexokinase isoenzymes (HK)
what is the first step in the utilization of glucose for storage for energy metabolism
conversation of glucose to G-P-6 via hexokinase isoenzymes through phosphorylation
phosphorylation of glucose effect —
makes it difficult for it to leave the cell
where are sodium dependent glucose transports (SGLT) found
intestinal mucosa
proximal tubule of nephron
which sodium dependent glucose transporter is found in intestinal mucosa
SGLT1
which sodium dependent glucose transporter is found in proximal tubule of nephron
SGLT2
SGLT2 allows for
reabsorption of glucose
Insulin secretion is stimulated by
glucose (primarily)
amino acids and ketoacids (weakly) via the citric acid cycle
insulin secretion is caused by (think about ions)
closure of K+/ATP channel and opening of voltage-gated calcium channel
how many sulfonylurea receptors are present on K+/ATP channel
4
function of sulfonylurea receptors on K+/ATP channel
they stimulate closure –> increase insulin release
