5. Pancreas

1
5. Pancreas

• has both exocrine (acini secrete digestive
  enzymes) and endocrine function (islets of
  Langerhans)
• control responds to blood glucose levels
  (humoral)
• hormones are polypeptides (proteins)

http//www.usc.edu/hsc/dental/ghisto/end/c_49.html
2
5. Pancreas

• major cell types
• alpha cells secrete glucagon
• beta cells secrete insulin
• delta cells secrete somatostatin (which inhibits
  insulin and glucagon secretion, and decrease fat
  absorption in intestines)
• F cells regulate exocrine function of pancreas
  (secrete pancreatic polypeptide)

3
5. Pancreas Glucagon

• actions hyperglycemic (increases blood glucose)
• stimulates formation and release of glucose from
  liver (main target)
• glycogenolysis - breakdown of glycogen (storage
  form of glucose)
• gluconeogenesis - formation of glucose from
  noncarbohydrate molecules (e.g., amino acids,
  glycerol, lactic acid)
• stimulates glycogenolysis in skeletal muscle
• stimulates triglyceride breakdown in adipose
  tissue (fat mobilization)

4
5. Pancreas Glucagon

• control
• secreted in response to low blood sugar, rising
  amino acid levels in blood
• inhibited by increased blood glucose and by
  somatostatin

5
5. Pancreas Insulin

• actions hypoglycemic (lowers blood glucose)
• increases transport of glucose into muscle and
  fat cells (NOTE does not increase uptake by
  brain, liver, or kidney)
• inhibits breakdown of glycogen and formation of
  glucose from amino acids or fatty acids (inhibits
  glycogenolysis and gluconeogenesis)
• promotes formation of glycogen (liver, skeletal
  muscles), protein synthesis (muscle), and fat
  synthesis and storage (adipose)

6
5. Pancreas Insulin (Control)

• stimulated by
• increased blood glucose
• increased blood amino acid and fatty acid levels
• parasympathetic impulses
• hyperglycemic hormones (GH, glucagon,
  epinephrine, thyroxine, glucocorticoids)
  indirectly result in insulin secretion by
  increasing blood glucose levels
• inhibited by
• low blood glucose and by somatostatin
• sympathetic impulses

7
(No Transcript)
8
5. Pancreas Insulin - Disorders Diabetes
Mellitus (DM)

• hyposecretion (or hypoactivity) of insulin
• body cells not stimulated to take up glucose
• hyperglycemia (excess blood glucose)
• very high glucose --gt nausea --gt fight-or-flight
  response --gt secretion of hyperglycemic hormones
  (epi, NE adrenal medulla, glucocorticoids
  adrenal cortex) --gt stimulates gluconeogenesis,
  lipolysis, glycogenolysis --gt adds to already
  high glucose
• not all sugar reabsorbed from urine --gt glucose
  lost in urine (glucosuria) --gt increased water
  loss --gt excessive urine production (polyuria)
  and excessive thirst (polydipsia)

9
5. Pancreas Insulin - Diabetes Mellitus

• cells use fats as energy source (due to poor
  glucose uptake)
• hyperglycemic hormones stimulate fat mobilization
  --gt fats in blood (lipidemia) --gt increase in
  lipid metabolites in blood (ketone bodies, which
  are strong organic acids) --gt decrease blood pH
  (ketoacidosis) and ketone bodies in urine
  (ketonuria)
• decreased blood pH --gt severe depression of
  nervous system --gt deep breathing --gt diabetic
  coma --gt death
• polyphagia (excessive hunger) - final sign, due
  to use of fats and proteins as energy sources

10
Type I Diabetes mellitus

• also called insulin-dependent diabetes (IDDM
  formerly juvenile onset diabetes)
• onset is sudden, usually before age 15
• may be due to autoimmune attack of proteins in
  beta cells result is lack of insulin activity
• lipidemia (high blood lipid content) and
  increased cholesterol lead to long-term vascular
  problems (arteriosclerosis, strokes, heart
  attacks, renal shutdown, gangrene, blindness)
• treated with insulin injections or pancreatic
  islet transplant (newer technique)

11
Type II Diabetes Mellitus

• non-insulin-dependent (NIDDM formerly
  mature-onset diabetes)
• usually starts after age 40
• insulin levels are normal or elevated, but
  peripheral tissue become less sensitive to it
• 25-30 of Americans carry gene that predisposes
  them to NIDDM, more likely in over-weight people
  (90 of cases)
• adipose cells secrete tumor necrosis factor alpha
  that depresses production of protein needed for
  glucose uptake
• often controllable with diet and exercise

12
Hyperinsulinism

• excess of insulin (usually from injection of
  excess)
• causes hypoglycemia --gt secretion of
  hyperglycemic hormones (to raise blood glucose)
  -? low glucose to brain --gt anxiety, nervousness,
  tremors, weakness --gt eventually, disorientation,
  convulsions, death due to insulin shock
• treated by providing sugar source