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Phys II Unit II > 6 Pancreas > Flashcards

6 Pancreas Flashcards

1
Q

What are the endocrine parts of the pancreas called?

A

Islets of langerhans - islands of endocrine cells (roughly 1 mil) in a sea of exocrine (digestive enzyme excreting) tissue

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2
Q

What are the 5 types of endocrine cells in the islets of langerhans?

A 
ß cells (60%) —> INSULIN
Alpha cells (25%) —> GLUCAGON
Delta cells (10%)
Gamma cells (4%)
Epsilon cells (1%)
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3
Q

What are the dominant hormonal regulators produced by the pancreas

A

Insulin (produced by ß cells) and Glucagon (produced by a cells)

Shift the body between anabolism and catabolism/glucose sparing

Generally oppose each other

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4
Q

What do delta cells of the islets of langerhans secrete?

A

Somatostatin (inhibits digestive function, GHIH)

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5
Q

What do gamma cells of the islets of langerhans secrete?

A

Pancreatic polypeptide (putatively reduces appetite and food intake)

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6
Q

What do epsilon cells of the islets of langerhans secrete?

A

Ghrelin (appetite stimulating hormone)

When you’re grilling, the smell makes you release Ghrelin

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7
Q

Besides Insulin, what else do beta cells release?

A

Amylin - acts on the CNS to suppress appetite

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8
Q

What does proinsulin look like?

A

Alpha and beta peptide chains connected by a C-peptide.

The alpha and beta chains are linked by 2 disulfide bonds.

The c-protein is cleaved from the proinsulin to form insulin

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9
Q

C-peptide is a marker of…

A

Insulin production and ß-cell function.

Used therapeutically to determine ß-cell function (because exogenous insulin doesn’t have c-peptide)

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10
Q

How does glucose stimulate insulin release?

A

Excitation-secretion coupling in ß-cells

Glucose enters via GLUT2 (facilitated diffusion)
Glucose+PO43 —> glucose-6-phosphate (trapped)
ATP closes K+ channel
Decreased K+ flux depolarizes cell membrane
Voltage-gated Ca2+ channels open
Ca2+ enters ß-cell and triggers exocytosis of insulin vesicles
Insulin secreted into circulation

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11
Q

Effect of insulin on carbohydrate stores

A 
Decreased blood glucose and storage
Increased glucose uptake by skeletal muscle and adipose tissue
Glycogenesis (skeletal muscle and liver)
Glycogenolysis (liver)
Gluconeogenesis (liver)
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12
Q

Effect of insulin on lipid stores

A

Decreased blood fatty acids and increased storage
Increased glucose uptake into adipocytes
Increased enzymes that produce fatty acids (increased lipogenesis)
Increased fatty acid uptake
Decreased lipolysis

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13
Q

Effect of insulin on protein stores

A

Decreased blood amino acids and increased storage
Increased amino acid uptake
Increased protein-synthesizing machinery
Decreased protein degradation

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14
Q

Insulin recruits ______ to cell surface

A

GLUT4: insulin dependent transporter in most other cells of the body

Other non-insulin dependent GLUT transporters:
GLUT1: BBB
GLUT3: neurons

GLUT2 is also insulin dependent GLUT4 is the main one to think of

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15
Q

What is the consequence of low levels of insulin secretion on glucose uptake?

A

Glucose transporters can’t get to surface of the cell and therefore can’t take up glucose

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16
Q

Insulin stimulates __________ pathways to regulate numerous possible intracellular pathways

A

MAP kinase

Can lead to general gene expression, cell growth, differentiation and other processes

Disruption of intracellular signaling is key to understanding insulin resistance and Type II DM

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17
Q

Most common endocrine disorder?

A

Diabetes Mellitus - results form high blood sugar levels over a prolonged period

18
Q

Type I DM is also known as…

A

Insulin dependent DM - due to lack of insulin secretion

Autoimmune: T-lymphocytes destroy ß-cells

Can also be idiopathic or environmental

19
Q

Type II DM is also known as

A

Non-insulin dependent DM - due to tissue resistance to insulin

Can be mild to severe

Often the result of life-style choice

Acute: characteristic of post-absorptive state

Chronic: includes a range of symptoms culminating in death

20
Q

Diagnosis of DM is through measurement of …

A

Glycated hemoglobin, HbA1c

Value of >6.5% HbA1c reflects above average blood glucose over the previous 3 months

21
Q

By what mechanism does DM cause polyphagia and polydipsia?

A

Hyperglycemia results from inadequate uptake of glucose into cells and an increased output of glucose from liver

Elevated glucose in the glomerular filtrate is greater than what the tubular cells can reabsorb

The osmotic effect of glucosauria draws additional water into the filtrate

Excess fluid lost from the body results in dehydration

Polyphagia occurs as a consequence of increase in appetite (cells are starving b/c glucose not getting in - GLUT4 not active)

Polydipsia occurs in an attempt to compensate for effects of dehydration

22
Q

The chronic dehydration resulting from DM eventually leads to what?

A

Dehydration state results in decreased blood volume

Peripheral circulatory failure can affect several vita organs

Renal failure may occur when GFR declines due to inadequate filtration pressure

Brain function declines resulting in failure to oxygenate the brain —> DEATH

Cells in the body shrink due to an osmotic shift of water into ECR and blood

Nerve cells lose their ability to maintain correct membrane potentials and form action potentials

23
Q

In DM patients, large-scale mobilization of fatty acids from triglyceride stores leads to what?

A

Hepatic use of fatty acids —> kenos is

Ketone bodies in the blood disrupt blood pH resulting in METABOLIC ACIDOSIS

Respiratory ventilation may increase in an effort to vent CO2 and shift pH up

Severe acidosis may depress brain function —> COMA —> DEATH

24
Q

How is hyperglycemia aggravated in DM patients?

A

Lack of insulin results in a shift towards more protein catabolism

Muscles atrophy and weight loss occurs

In children, proper growth is compromised

Excess blood amino acids shift towards greater gluconeogenesis in teh liver, contributing to the existing hyperglycemia

25
Q

How does insulin excess occur?

A

Insulin overdose (insulin shock) - a sugary snack will recover normal blood glucose

Reactive hypoglycemia - in an extreme response to glucose, beta cells release too much insulin; DON’T give sugary snack but control by limiting carbs in diet

Use C-peptide levels to determine which it is if you don’t know

Effects are dangerous - can lead to depressed brain function and LOC

26
Q

Glucagon is stimulated by …

A

Low glucose

Epinephrine***

Vagal stimulation***

27
Q

Glucagon is inhibited by…

A

High glucose

Somatostatin***

28
Q

What IS glucagon?

A

14 amino acid polypeptide expressed in liver, intestine, brain and pancreas

Produced as proglucagon and proteolytically process to yield glucagon and incretin (GLP1)

GLP1 is released from intestine in response to high glucose levels in teh intestine

GLP1 increases insulin release from ß-cells

29
Q

Glucagon mainly targets ________ to stimulate________.

A

Liver —> hepatic glucose output

It INCREASES PLASMA GLUCOSE LEVELS

Opposes the effects of insulin and GLP1
Increases gluconeogenesis and glycogenolysis
In adipose tissue, has a pro-lipolysis effect

30
Q

Glucagon release is…

A

Increased by hypoglycemia**

Increased by epi, CCK, vagal stimulation, fasting, exercise

Decreased by hyperglycemia, somatostatin, insulin, fatty acids, and keto acids

Increased by dietary protein (ARGININE), in absence of carbs (if a meal is a combo of protein and carbs, no effect on glucagon, but A STEAK —> increased glucagon)

31
Q

Glucagon effects on carbohydrate stores

A

Increase blood glucose
Increased gluconeogenesis and release
Increased glycogenolysis
Decreased glycogen synthesis

32
Q

Glucagon effects on lipid stores

A

Increased blood fatty acids and ketones
Decreased triglyceride synthesis
Increased lipolysis and release of fatty acids from adipose tissue
Increased ketone production

33
Q

Glucagon effects on protein stores

A 
Minimal effect on blood amino acids
Decreased hepatic protein synthesis
Increased hepatic protein degradation
Increased gluconeogenesis
No effect on skeletal muscle proteins, the major protein storage site
34
Q

What is somatostatin?

A

14 amino acid polypeptide hormone produced in the delta cells

Release stimulated by high fat, carbs, and protein-rich meals

Release in the pancreas not well understood, but inhibits the release of insulin and glucagon by hyperpolarizing the beta and alpha cells (paracrine effect)

Has generalized inhibitory effects on the GI tract (smooths out the spikes in blood glucose that can occur with meals)

Well-known brain peptide released in the median eminence of the hypothalamus to inhibit the release of GH by anterior pituitary

35
Q

How else is glucose regulated (besides insulin and glucagon)?

A 
Diabetogenic hormones:
Epinephrine
Cortisol
GH and IGF-1
(Thyroid Hormone) - not very responsive, onset too slow

The brain: hypothalamic control of fuel management
• Autonomic control of hormone release
• Senses nutrients and hormones associated with nutrient levels

36
Q

Epinephrine effects on blood glucose

A

Increased glycogenolysis, gluconeogenesis and glucagon secretion

Decreased insulin secretion via alpha-adrenergic stimulation of beta cells

37
Q

Cortisol effects on blood glucose

A

Increase gluconeogenesis and glucose sparing (use fatty acids instead)

Decreased glucose uptake in tissues other than the brain

In liver, promotes glycogenolysis in early-stage fasting and glycogen synthesis in late-stage fasting

38
Q

GH effects

A

On blood glucose - decreased glucose uptake by muscles and increased glucose sparing

On fatty acids - increased lypolysis

On amino acids - increased uptake into cells, decreased blood amino acids

On muscle protein - Increased protein synthesis, decreased protein degradation, increased DNA/RNA synthesis

Released during deep sleep, stress, exercise, hypoglycemia

Promotes growth, SMALL ROLE in fuel metabolism

39
Q

What are the main areas of the brain involved in neural control of glucose?

A

CNS has receptors for nutrient levels, esp glucose detection in ARCUATE NUCLEUS, and hormones

The hypothalamus directly and indirectly regulates glucose homeostasis by:
• Insulin and glucagon secretion (via ANS0
• Hepatic glucose output
• Glucose uptake by skeletal muscles

Pathways that regulate glucose balance integrate with brain circuits that control energy balance and control body weight

40
Q

What is a positive energy balance?

A

Food intake exceeds energy expended

Remaining stored as adipose tissue

41
Q

What is a negative energy balance?

A

Food intake does not meet energy needs

Body supplies remainder

42
Q

__________ are primarily responsible for regulating food intakes and body composition

A

Hypothalamic brain centers

Phys II Unit II (9 decks)

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