Endocrine Pancreas (Histology & Physiology) Flashcards
secretory products of endodocrine pancreas
Insulin & Glucagon
cells that produce glucagon
Alpha cells
cells that produce insulin
beta cells
cells that produce somatostatin
delta cells
cells the produce pancreatic peptide
F cells aka PP cells
Insulin synthesis rxn
proinsulin –> insulin & C-peptide
location of alpha, beta, delta, F cells
Islet of Langerhans center(ish) B cells peripheral inner ring(ish) D cells peripheral outer ring(ish) A cells
1
exocrine pancreas with secretory acini
2
islet of Langerhans
3
duct of the exocrine pancreas.
4
connective tissue septae
What do Beta cells contain & produce
membrane-limited secretory granules with highly electron dense core. Full of insulin.
General structure of insulin
peptide of 21 AAs in beta chain, 30 AAs linked by two disulphide bonds
Major stimuli for insulin secretion (5)
- ____ plasma glucose concentration
- ____ plasma amino acids
- ____ GI hormones (“gut factors”; probably mainly GIP).
- ____ parasympathetic activity ,
- ____ sympathetic activity (by SNS nerves to pancreas + circulating epinephrine)
Major stimuli for insulin secretion (fill in blanks)
- ____ plasma glucose concentration
- ____ plasma amino acids
- ____ GI hormones (“gut factors”; probably mainly GIP).
- ____ parasympathetic activity ,
- ____ sympathetic activity (by SNS nerves to pancreas + circulating epinephrine)
Major stimuli for insulin secretion
- __^__ plasma glucose concentration
- __^__ plasma amino acids
- _^___ GI hormones (“gut factors”; probably mainly GIP).
- _^___ parasympathetic activity ,
- __v__ sympathetic activity (by SNS nerves to pancreas + circulating epinephrine)
Major stimuli for glucagon secretion (4)
Major stimuli for glucagon secretion
- ____ plasma glucose concentration
- ____ plasma amino acids: Role: to prevent sudden hypoglycemia (from amino acid-induced insulin secretion) if you eat a high protein meal without carbohydrates, e.g., a piece of meat.
- Other stimuli -see text Figure
- NOTE: during & after a normal meal; you seldom see a change in [glucagon] when measured in PERIPHERAL BLOOD
Major stimuli for glucagon secretion (fill in blanks)
- ____ plasma glucose concentration
- ____ plasma amino acids: Role: to prevent sudden hypoglycemia (from amino acid-induced insulin secretion) if you eat a high protein meal without carbohydrates, e.g., a piece of meat.
- Other stimuli -see text Figure
- NOTE: during & after a normal meal; you seldom see a change in [glucagon] when measured in PERIPHERAL BLOOD
Major stimuli for glucagon secretion
- __v__ plasma glucose concentration
- __^__ plasma amino acids: Role: to prevent sudden hypoglycemia (from amino acid-induced insulin secretion) if you eat a high protein meal without carbohydrates, e.g., a piece of meat.
- Other stimuli -see text Figure
- NOTE: during & after a normal meal; you seldom see a change in [glucagon] when measured in PERIPHERAL BLOOD. in peripheral blood. Probably not true in pancreas blood, but that goes through liver & is filtered out.
Where is majority of insulin consumed & degraded?
Liver (80%) & degraded there & kidney.
Where does insulin go after release from pancreas?
directly through liver
Where does glucagon act?
almost totally on liver
peripheral blood insulin and glucagon levels?
low and very low
effect of insulin on brain? Intestinal mucosa? RBCs? Kidney tubules?
none except part of hypothalamus. No. No. No.
speed & duration of glucagon
fast & short
hepatic actions of glucagon:
overall effect on glc production & secretion? plasma glc conc?
__^__ glycogenolysis·
___^_ amino acid uptake
___^_ gluconeogenesis
__^__ ketoneogenesis
glc production v, plasma glc v
Glucagon & catecholamines need what to act first for optimal function in liver?
cortisol
glucagon inflence on phosphorylase and glycogen synthetase activities?
Increase in phosphorylase activity
Decreases glycogen senthetase activity
Insulin effect on glc uptake? synth of enzymes?
faster, slower
potency of insulin compared to other hormones?
MOST, BEST, STRONGEST
Insulin effects on anti-catabolic processes: what’s it do to these processes?
____ protein degradation
____ glycogenolysis
____ gluconeogenesis
____ lipolysis
__v__ protein degradation
__vv__ glycogenolysis
__v__ gluconeogenesis
__vv__ lipolysis
Insulin effects in MUSCLE:
____ glucose uptake; mechanism
____ amino acid uptake
____ ribosomal protein synthesis: CONTROVERSIAL:
___ribosomal PS in some animals (in vivo & in vitro);
but ________ on human forearm muscle in vivo
____ synthesis of lipoprotein lipase (extracts FA from VLDL & chylomicrons) - these FAs are then used (preferentially to glucose) for energy generation by muscle
____ protein breakdown
____ release of amino acids
^ glc uptake (transporters in waiting)
^ aa uptake
^ protein synth (controversial, ^, not on human forearm muscle, so contradicting info)
^ synth of LPL
V protein brekdown
V release of aa
Insulin effects in ADIPOSE:
____ glucose uptake
____ fatty acid synthesis (from glucose)
____ a-glycerol phosphate synthesis (from glucose)
____ synthesis of lipoprotein lipase (extracts FA from VLDL & chylomicrons)
____ TAG synthesis (from FA and a-glycerol phosphate)
____ lipolysis ( ___ activity of “hormone-sensitive lipase”)
__^__ glucose uptake
__^__ fatty acid synthesis (from glucose)
__^__ a-glycerol phosphate synthesis (from glucose)
__^__ synthesis of lipoprotein lipase (extracts FA from VLDL & chylomicrons)
__^^^__ TAG synthesis (from FA and a-glycerol phosphate)
__vvv__ lipolysis ( ___ activity of “hormone-sensitive lipase”)
Insulin effects in LIVER:
___ release of glucose
___ lipid synthesis > TAG
but insulin > ___ synthesis of VLDL (& its apo B) and secretion of VLDL. THUS, insulin ___ hepatic TAG stores. This allows smooth transition in TAG metabolism from feeding (CMs) to fasting (VLDLs).
___ protein synthesis
___ ketogenesis
__v_ release of glucose
__^_ lipid synthesis > TAG
but insulin > __v__ synthesis of VLDL (& its apo B) and secretion of VLDL. THUS, insulin __^_ hepatic TAG stores. This allows smooth transition in TAG metabolism from feeding (CMs) to fasting (VLDLs).
__^_ protein synthesis
__v_ ketogenesis
effect of insulin on target cell sensitivity?
decrease
effect of glucagon on target cell sensitivity to insulin?
decreases, but opposite effect in liver!
effect of epi & norepi on target cell sensitivity to insulin?
decreases, but opposite effect in liver!
effect of GH, Cortisol, T3 on target cell sensitivity to insulin?
decrease, decrease, increase
Effect of X on Beta cell excretion of insulin?
X = glucagon
Epi/norepi
GH
Cortisol
T3
v
^ (indirect)
^ (indirect)
^ (indirect)
