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47 Cards in this Set

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Exocrine Pancreas does what?
-Secretes ENZYMES to the gut

-Absorption of nutrients
Endocrine Pancreas does what?
- Secretes HORMONES into the pancreatic vein, which connects to the hepatic portal vein.

- Hormones are carried to the liver and beyond.

- These hormone aid in nutrient utilization by the body
Roles of the Endocrine Pancreas in Whole Body Physiology
- To regulate whole body macronutrient metabolism.
- Macronutrients are
carbohydrate (glucose),
fat (lipid) and protein
(amino acids).

- To coordinate whole body metabolism with ingestion of meals and the lack of food.
Macronutrients control ___ ____ __ ______ of the endocrine pancreas
the secretion of hormones
Islets of Langerhans is what % of the pancreas?

Cell Types?
~1% of pancreas

Cell types:
Alpha, Beta, Delta,

also F-cells
Islets of Langerhans Cell type: Alpha
- 25% of islet

- Glucagon
Islets of Langerhans Cell type: Beta
- 60% of islet

-Insulin
Islets of Langerhans Cell type:Delta
- 10% of islet

- Somatostatin
Islets of Langerhans Cell type:F-cells
- 1% of islet

- Pancreatic Polypeptide
Blood Glucose Controls Insulin and Glucagon Secretion:

Insulin secretion increases
as ...
blood levels of
glucose increase
Blood Glucose Controls Insulin and Glucagon Secretion:

Glucagon secretion
decreases as ...
blood levels of glucose increase
How Does Glucose Regulate
Insulin Secretion?
- Glucose metabolism
regulates insulin secretion

- Glucose is not a hormone, it is a nutrient
The 9 steps in which Glucose Regulates Insulin Secretion
1. Glucose enters cells through a Glucose Transporter #2 (Glut2)

2.Glucose enters glycolysis,
via Glucokinase

3.Glucose metabolism increases cellular ATP and NADPH levels.

4.Increased ATP closes ATP-sensitive K+-channels, decreasing K+.export.

5.Increased intracellular K+ depolarizes the membrane, resulting in opening of
Ca+2-channels

6.Increased intracellular free Ca+2 activates exocytosis of the insulin-containing secretory granules

7. Insulin is secreted

8.Glucagon and
cholecystokinin (CCK)
stimulate insulin
secretion.
- CCK increases intra-
cellular Ca+2
- Glucagon increases
cAMP.]
9. Somatostatin inhibits
insulin secretion.
Factors Stimulating Insulin Secretion:
- Food intake
- Glucagon
- Vagal Stimulation
- Gut Hormones
Factors Stimulating Insulin Secretion: Food Intake
- Carbohydrate(Glucose),
- Protein (Amino acids)
- Fat (fatty Acids)
Factors Stimulating Insulin Secretion:Glucagon
(alpha-cells)
Factors Stimulating Insulin Secretion:Vagal Stimulation
beta-adrenergic
Factors Stimulating Insulin Secretion:Gut hormones
- CCK

- GIP (glucose insulinotropic peptide)

- GLP-1,glucagon-like peptide-1
Factors Inhibiting Insulin Secretion
- Low Blood Glucose
[Fasting Starvation]

- alpha-Adrenergic

- Somatostatin
Factors Stimulating Glucagon Secretion:
- Low blood glucose
- fasting/starvation
- exercise
- catacholamine (b-adrenergic)
- Cortisol,
- Vagal stimuli
Factors inhibiting Glucagon Secretion:
- high blood glucose
- food intake
- fatty acids
- Somatostatin
- Insulin
- a-adrenergic
what is known
about the mechanics
of glucagon secretion?
not much
Role of Insulin and Glucagon
in the Control of Blood Glucose.
- Insulin will stimulate cellular uptake of glucose.
- This is achieved by regulating the facilitative transport of glucose into muscle and fat cells.

- Glucagon will stimulate the release of glucose from cells, mainly liver.
Active Transport of Glucose into Cells requires:
ATP

-In the intestine, Glucose-Na+ co-transporter
Facilitative Transport of Glucose into Cells:
does not require ATP

- At least 8 subtypes, #1-8

- Pancreatic b-cells and Liver: Glut2, not insulin regulated

- Muscle, Fat Cells: Glut4, Insulin regulated.
What facilitative transport is not insulin regulated?
Pancreatic b-cells and Liver: Glut2, not insulin regulated
What facilitative transport is insulin regulated?
- Muscle, Fat Cells: Glut4, Insulin regulated.
Insulin-Regulated Transport of Glucose into Muscle and Fat Cells
1. Glut4 is a membrane bound protein: the plasma membrane and intracellular membranes.

2. Insulin binding to its receptor induces the translocation of Glut4 from intracellular sites to the plasma membrane.
* This increases the capacity for glucose transport.

3. When blood insulin levels decline Glut4 is returned to intracellular Membranes.
*This decreases the capacity for glucose transport.
The Facilitative Transport
of Glucose into b-cells and Liver facts
- Glut4 is in the muscle and adipocytes, but not liver or b-cells

- Glut2 is a glucose transporter expressed in b-cells and liver.

- Glut2 is not insulin regulated
Glut2 is a
glucose transporter expressed in b-cells and liver.
Glut2 is not _______ regulated
insulin
Glut4 is in _____ & ______, but not _______ or ________
- the muscle and adipocytes

- liver or b-cells
Insulin Stimulates
Glucose Uptake, Utilization and Storage as Glycogen and Fat.
Glucagon Stimulates ?
Hepatic Glucose Production, Hepatic, Fatty Acid Oxidation & Ketone Synthesis
Why Manage Blood Glucose?
- The central nervous system (CNS) uses glucose for fuel
- 6 g Glucose/hour.

- Glucose utilization by the CNS is not insulin regulated.

- Blood levels of glucose are regulated by multiple hormones
If the brain does not get enough glucose from the blood:
.
- Brain will sense hypoglycemia and initiate a response to get more glucose.

- The brain can use ketones as an alternative fuel source. Ketones are derived from hepatic lipid oxidation. Hepatic lipid oxidation increases in starvation and uncompensated type I diabetes
Ketones are derived from
hepatic lipid oxidation.
Hepatic lipid oxidation increases in?
starvation and uncompensated type I diabetes
If blood glucose is too high, i.e., in uncompensated type I diabetes,
- Elevated glucose and ketone create a hyperosmotic state and will promote tissue dehydration, e.g., CNS.

- This, coupled with the acidosis resulting from excess ketones, will have severe effects on CNS function.

- Remedy: insulin treatment, activate Osmoreceptors to stimulate the thirst center & enhance vasopressin secretion to prevent loss of water
An Experiment:

Insulin administration
to a rat (IP, intraperitoneal)
will induce a prompt
decline in blood glucose.

- Insulin stimulates
glucose uptake by cells.

- Insulin activates Glut4.

- After ~30 mins, blood glucose levels increase.

The animals are given no food.

How can blood glucose levels
increase?
Blood glucose levels
rise because of
stimulated release
of glucose from cells;
Mainly liver.

- Glucagon and Epinephrine
induce Glycogenolysis
(glycogen breakdown)
and Gluconeogenesis
(glucose synthesis).

Cortisol and
Growth hormone
block insulin
stimulated glucose
uptake by muscle
and adipose cells.

This makes glucose
available to the CNS
What is Glycogenolysis ?
glycogen breakdown
What is Gluconeogenesis?
glucose synthesis
What counters the Action of Insulin
Glucagon, Epinephrine, Cortisol & Growth Hormone
What elevates blood glucose?
Glucagon, Epinephrine, Cortisol & Growth Hormone
What lowers blood glucose
Insulin and diet
Facts on Diabetes-type 1
- Type I, insulin dependent diabetes mellitus (IDDM), Juvenile diabetes

- Typically occurs in the young

- mean age 10-14 year

- 0.26% of the US population

- Beta-cell destruction,

- autoimmune disorder

- Symptoms: Elevated blood glucose, Polydypsia: frequent drinking, osmotic stress
Polyuria: frequent urination

- Treatment: Hormone replacement thearpy:
-INSULIN,
-recombinant insulin,
-Humulin (Lilly)
Facts on Diabetes-type II
- Type II, non-insulin dependent diabetes mellitus (NIDDM), adult onset diabetes

- Occurs in the adult population:

- 1-2% of the US population

- Often (but not always)
associated with obesity
- Tissue resistance to insulin, i.e. insulin resistance
- a post-receptor defect
requires increased
insulin levels to
achieve desired
biological effect

- Treatment:
- give insulin replacement
- increase insulin
secretion using
sulfonylureas drugs
- increase exercise and
decrease caloric intake,
particularly fat.