pancreas physiology Flashcards
what is anabolism
build up or synthesis of larger organic macromolecules
do anabolic reactions require energy
yes
what is the storage form of glucose
glycogen
what is catabolism
breakdown of large molecules
what is glycogenesis
glucose to glycogen
what effect does glycogenesis have on glucose
decrease
what is glycogenolysis
glycogen to glucose
what effect does glycogenolysis have on glucose
increase
what is gluconeogenesis
amino acids to glucose
what effect does gluconeogensis have on glucose
increase
where is excess glucose stored
in the liver and muscle
what is excess glucose stored as
glycogen
what is additional glucose transformed into
fatty acids and glycerol
what is glycerol used to synthesise
triglycerides
what is triglyceride made up of
glycerol with three fatty acids attached
where is triglyceride mostly
in adipose tissue
what are excess amino acids converted to
glucose and fatty acids (stored as triglyceride)
what can glycerol be converted to
glucose by the liver
what plays an important role in maintaining normal blood glucose
liver
what is primary energy storage site
adipose tissue
what does adipose tissue regulate
fatty acid levels
what is muscle the primary site of
amino acids storage
where is glycerol from
triglycerides hydrolysis
during prolonged starvation what does the brain use instead of glucose
ketones
what are the dominant hormonal regulators that shift the metabolic pathway
insulin and glucagon
what 2 types of tissue is the pancreas made up of
endocrine and exocrine
what does the exocrine portion secrete
watery, alkaline solution and digestive enzymes
what are the endocrine cells called
islet of Langerhans
what is the most abundant endocrine cell
beta cells
what do beta cells. produce
insulin
what do the alpha cells produce
hormone glucagon
what do delta cells produce
somatostatin
what is the least abundant endocrine cell
F cells
what do F cells secrete
pancreatic polypeptide
what does pancreatic polypeptide play a role in
reducing appetite and food intake
where are the beta cells mostly
in the centre
what does somatostatin do
inhibit the digestive system
what secretes somatostatin
D cells
when is somatostatin released
in response to an increase in blood glucose and blood amino acids
what kind of system does somatostatin regulate via
paracrine
where else is somatostatin produced
in hypothalamus
what does somatostatin released from hypothalamus do
inhibits secretion of growth hormone and TSH
what is the overall outcome of insulin
to lower blood glucose levels and promote their storage
what effect does insulin have on glycogen synthase
increases its activity
what effect does insulin have on glucose transport
facilitates glucose transport into most cells
what effect does insulin have on glucose storage
stimulates glycogenesis (production of glycogen from glucose in both skeletal muscle and liver)
how does insulin affect glycogenolysis
inhibits it favouring storage
how does insulin affect blood glucose
decrease it by promoting cells uptake of glucose from the blood for use and storage
what is the only hormone capable of lowering blood glucose
insulin
how is glucose uptaken by cells
by glucose transporters (GLUT)
what happens to glucose once it is transported into a cell
immediately phosphorylated into glucose-6-phosphate
what does GLUT 1 do
transport glucose across the blood brain barrier
what does GLUT 2 do
transfers glucose into kidney and intestinal cells by means of the sodium and glucose co transporter
what does GLUT 3 do
main Transporter of glucose into neurons
what glucose transporter is responsible for majority of glucose uptake
GLUT 4
what is the only transporter that responds to insulin
GLUT 4
what happens when insulin binds toto a receptor that acts as a tyrosine kinase enzyme
it induces these vesicles to move too the plasma membrane and fuse with it, thus inserting GLUT 4 molecules into the plasma membrane
what happens to the glucose transporters when insulin secretion decreases
the glucose transporters are retrieved from the membrane by endocytosis and returned to the intercellular pool
what tissues do not depend on insulin for their glucose uptake
the brain, working muscle and liver
how does the brain constantly get its glucose supply
via GLUT 1 and GLUT 3 molecules
what GLUT transporter supplies the muscle
GLUT 4
does the liver use GLUT 4
no
how does insulin lower blood fatty acids
- enhances the entry of fatty acids from the blood into adipose tissue cells 2. increase the transport of glucose into adipose tissue cells via GLUT 4 3. promotes chemical reactions that use fatty acids and glucose for triglyceride synthesis 4. inhibits lipolysis (fat breakdown) reducing the release of fatty acids from adipose tissue into the blood
how does insulin lower blood amino acid levels
- promotes active transport of amino acid from the blood into muscle and other tissue (this provides building blocks for protein synthesis) 2. increases the rate of amino acid into protein by stimulating protein synthesising 3. inhibits protein degradation
what does an increase in blood glucose stimulate beta cells to do
synthesise and release insulin
what does the increased insulin do
reduce blood glucose to normal and promote use and storage of glucose
what does a fall in blood glucose do to insulin
inhibits insulin secretion
how does glucose enter beta cells
through GLUT 2
what happens to glucose once it enters the beta cell
glucose is immediately phosphorylated to glucose-6-phosphate
what happens to the glucose 6 phosphate
it is oxidised by the beta cell to yield ATP
what 2 channels does the beta cell have
- ATP K+ channel - voltage gated Ca2+ channel
is ATP K+ channel open or closed when ATP is bound
remains open unless ATP binds to it
what happens to the K+ channel when ATP is generated form glucose-6-phosphate
K+ channel closes
what happens now the K+ channel is closed
the cell depolarises
now the cell depolarises what happens to the Ca2+ channel
the Ca2+ channel now opens allowing Ca2+ entry
what happens now Ca2+ enters a cell
triggers exocytosis of secretory vesicles that contain insulin resulting in insulin secretion
how do amino acids affect insulin
they increase insulin secretion
what 2 GI hormones are released in response to food
- glucose dependent insulinotropic peptide (GIP) - glucagon-like-peptide (GLP)
what do GIP and GLP do
stimulate insulin secretion
what are incretins
hormones that notify the pancreatic beta cell of a rise in blood nutrients
what do incretins do
increase insulin secretion by increasing cAMP which enhances Ca2+ induced release of insulin
how does the parasympathetic affect insulin secretion
through acetylcholine acting through IP3/Ca2+ pathway (feedforward pathway)
how does sympathetic stimulate affect insulin secretion
inhibit insulin secretion by decreasing cAMP
DIABETES MELLITUS
DIABETS MELLITUS
what is diabetes term
inadequate insulin action
what happens in diabetes
blood glucose is elevated = hyperglycaemia
what is the urine like in mellitus
sweet
why is the urine sweet in diabetes mellitus
from excess blood glucose that spills into the urine
what is the urine like in patients with diabetes insipidus
not sweet
what are the 2 types of diabetes mellitus
type 1 (lack of insulin secretion) type 2 (normal or even increased insulin secretion but reduced sensitivity of insulin targets)
how does hyperglycaemia occur in diabetes mellitus
arises form reduced glucose uptake by cells
INCREASE IN BLOOD GLUCOSE
INCREASE IN BLOOD GLUCOSE
what is glucosuria
glucose in the urine
what does glucose in the urine cause
osmotic effect that draws water with it producing an osmotic diuresis
what is polyuria
frequent urination
what does excess fluid loss from the body lead to
dehydration
what can circulatory failure lead to
death because of low cerebral blood flow or secondary renal failure
what cells are especially sensitive to shrinking
brain cells
what is polydipsia
excessive thirst
why does polydipsia occur
to counteract dehydration
what happens in intracellular glucose deficiency
appetite is stimulated leading to polyphagia
what is polyphagia
excessive food intake
is there weight gain because of the polyphagia
no weight loss still occurs from the effects of insulin. deficiency on fat and protein metabolism
CONSEQUENCES OF FAT METABOLISM
CONSEQUENCES OF FAT METABOLISM
what is increased blood fatty acids used by cells as
an alternative energy source
what does increased liver use of fatty acids result in
excessive ketone bodies into the blood causing ketosis
what are ketone bodies
result of incomplete breakdown of fat during hepatic energy production
what does ketosis lead to
metabolic acidosis
what effect does acidosis have on the brain
depresses the brain and can lead to diabetic coma and death
what is a compensatory mechanism for metabolic acidosis
increase ventilation too blow off extra acid forming CO2
what symptoms is caused by blowing off ketones
fruity breath odour combination of fruit and nail varnish remover
CONSEQUENCES OF PROTEIN METABOLISM
CONSEQUENCES OF PROTEIN METABOLISM
how does a lack of insulin affect protein metabolism
results in protein catabolism
what does breakdown of muscle protein lead to
wasting and weakness of skeletal muscle
what does reduced amino acid uptake lead to
excess amino acids in the blood this causes an increase in gluconeogenesis and further aggravates hyperglycaemia
LONG TERM COMPLICATION
LONG TERM COMPLICATION
what is the most common cause of premature death in diabetes
cardiovascular lesions
what is the leading cause fo kidney failure and blindness
diabetes
why may patients limbs need amputated
due to impaired delivery of blood to the extremities
what is the best treatment for diabetes mellitus
continuously keep blood glucose levels within normal limits
INSULIN EXCESS
INSULIN EXCESS
what is the characteristic of excess insulin
hypoglycaemia
how can excess insulin occur
- when a diabetic patient injects too much insulin - blood insulin level rises too high in a non diabetic patient
what are the symptoms of hypoglycaemia
- tremor - fatigue - sleepiness - inability to concentrate
how to counteract hypoglycaemia
diabetic person should eat or drink something sugary
what happens if there is chronic insulin deficiency in a diabetic
diabetic ketoacidosis
ketoacidosis symptoms
- deep laboured breathing - fruity breath (from exhaled ketones)
GLUCAGON
GLUCAGON
what secretes glucagon
alpha cells
where is main site of glucagon action
liver
what does glucagon increase
cAMP
what does glucagon decrease
glycogen synthesis
what does glucagon promote
glycogenolysis and stimulates gluconeogenesis
effects of glucagon on fat
- promotes fat breakdown - inhibits triglyceride synthesis
what is glucagon the opposite of
insulin
what is the mainstay of glucagon actions
promotes catabolism of nutrient stores between meals to keep up the blood nutrient levels, especially blood glucose
what does glucagon work simultaneously with
insulin
EPINEPHRINE AND CORTISOL
EPINEPHRINE AND CORTISOL
what are the 2 stress hormones
epinephrine and cortisol
what do stress hormones do to blood glucose levels
increase it t
how does growth hormone affect glucose
increase glucose uptake by muscles
look at diagram
look at diagram
