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Endocrine Physiology - daves notes only so far > Glucoregulatory hormones > Flashcards

Glucoregulatory hormones Flashcards

1
Q

Glucose levels are usually very ….. …….. .

A

Closely controlled

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2
Q

Via what three mechanisms is glucose obtained?

A

Intestinal absorption, glycogenolysis(liver) and gluconeogenesis (liver and kidney)

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3
Q

Which tissues use glucose?

A

All tissues i.e. muscle, brain, adipose, RBCs, kidney

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4
Q

List the hormones that maintain glucose homeostasis

A

Insulin, glucagon, somatostatin, pancreatic polypeptide

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5
Q

Insulin can be thought of as…

A

a “storing” hormone - a hormone of fuel storage and anabolism

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6
Q

List the sequence of insulin synthesis

A

Preproinsulin, proinsulin (stored in granules), insulin in beta-pancreatic cells

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7
Q

How does insulin secretion occur? In response to what?

A

Exocytosis in response to increasing intracellular calcium

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8
Q

What blood level of glucose is required to stimulate increased insulin secretion?

A

Blood glucose levels >5mmol increase insulin secretion rapidly

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9
Q

List the stages via which a high blood glucose stimulates insulin secretion

A

Glucose -> glut-2->enters B cells -> increases ATP -> closes K+ channes -> depolarisation -> opens Ca2+ channels -> Ca2+ enters cells -> triggers exocytosis of insulin

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10
Q

Give six triggers for insulin secretion other than glucose

A
  • Arginine/leucine and other amino acids
  • cAMP (NB adrenalin lowers cAMP and therefore inhibits insulin release
  • Glucagon and theophylline via cAMP
  • Autonomic stimulation via acetyl chloride
  • GI hormones
  • Oral hypoglycaemic drugs (these close ATP sensitive K+ channels
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11
Q

List four gastrointestinal hormones that trigger insulin secretion

A

GIP, enteroglucagon, secretin, CCK

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12
Q

List the inhibitors of insulin secretion

A

Somatostatin, beta blockers, K+ depletion, thiazide diuretics (via negative feedback)

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13
Q

Why is the liver exposed to high levels of insulin?

A

Because it is secreted into the portal blood

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14
Q

What is the effect of insulin on adipose tissue?

A

Increased glucose entry, increased fatty acid synthesis, increased TG deposition, inhibition of lipoprotein lipase, increased K+ uptake

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15
Q

What is the effect of insulin on muscle?

A

Increased glucose entry, increased amino acid uptake, increased protein synthesis, increased protein catabolism

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16
Q

What is the effect of insulin on the liver?

A

Decreased ketogenesis, increased protein synthesis, increased lipid synthesis, decreased glucose output

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17
Q

What is the effect of insulin in general?

A

Cell growth, stimulates whole body glucose uptake (skeletal muscle, heart muscle, smooth muscle and adipose tissue)

18
Q

Which tissues do not respond to insulin?

A

Brain, liver, kidney, gut, RBCs, pancreatic B cells

19
Q

What are the consequences of insulin deficiency?

A

Diabetes mellitus (decreased glucose uptake into peripheral cells and increased plasma glucose)
Increased rate at which amino acids are catabolised
Protein deficiency
Poor resistance to infections
Ketosis ->acidosis -> coma

20
Q

How may glucagon be thought of?

A

A “mobilising” hormone

21
Q

Give the sequence of glucagon synthesis. Where does this occur?

A

Preproglucagon -> glucagon. Occurs in the A-pancreatic islet cells.

22
Q

Give the stimulants for glucagon secretion

A

Hypoglycaemia, aa, CCK, gastrin, cortisol, exercise, stress, infection, beta-adrenergic, theophylline

23
Q

Give the inhibitors of glucagon secretion

A

Glucose (seems to require insulin), somatostatin, secretin, FFA, ketones, insulin, GABA, alpha stimulators

24
Q

What are the cations of glucagon?

A

Primarily acts in the liver stimulating glycogen breakdown. In other tissues it stimulates lipolysis (adipose and liver). Inotropic to the heart, increases insulin secretion.

25
Q

What effect does glucagon have on muscle?

A

No effect.

26
Q

When and in what form is somatostatin secreted?

A

From D-cells, in two forms.

27
Q

What is the effect of somatostatin?

A

Inhibits insulin, glucagon, pancreatig polypeptied and can also inhibit GB contrition by decreasing CCK release

28
Q

When and from what is pancreatic polypeptide secreted?

A

After a protein meal, from F-cells

29
Q

How do catecholamines affect glucose homeostasis?

A

provide a fuel source.

30
Q

What other hormones affect glucose homeostasis?

A

Catecholamines, thyroid hormones, glucocorticoids, GH

31
Q

How do thyroid hormones affect glucose homeostasis?

A

Alternating functions ?!?!?!?

32
Q

How do glucocorticoids affect glucose homeostasis?

A

They increase blood glucose, increase protein breakdown, and cause insulin resistance

33
Q

How does growth hormone affect glucose homeostasis?

A

GH is diabetogenic, mobilising FFA, inhibiting glucose utilisation and inhibiting insulin receptor function.

34
Q

What is the general rule of thumb for hormonal control of glucose homeostasis?

A

Overall insulin lowers blood glucose while the other hormones raise it.

35
Q

What does insulin do during fasting?

A

Insulin protects against increased catabolism during fasting by decreasing gluconeogenesis, decreasing lipolysis, decreasing protein breakdown, decreasing hepatic ketogenesis.

36
Q

What does insulin do after feeding?

A

It has a sternly anabolic role and promotes storage.

37
Q

How does glucagon maintain blood glucose in fasting, exercise or stress?

A

It stimulates the liver to increase glycogen breakdown and increase glucose formation, and sets the liver for ketone production. After a protein meal it protects against insulin induced hypoglycaemia.

38
Q

What is adrenaline’s role in glucose homeostasis?

A

It is the most important defence against acute hypoglycaemia

39
Q

How does adrenaline protect against acute hypoglycaemia?

A

Adrenaline decreases glucose uptake, increases hepatic formation, decreases insulin release, and increases lipolysis and provides FFA

40
Q

What role does cortisone play in glucose homeostasis?

A

Cortisol promotes peripheral tissue breakdown and antagonises insulin

41
Q

What role does GH have in glucose homeostasis?

A

GH increases anabolism and decreases catabolism, and inhibits the effect of insulin, and stimulates lipolysis.

42
Q

What role does thyroid hormone play in glucose homeostasis?

A

Thyroid hormone stimulates lipolysis and increases blood glucose levels.

Endocrine Physiology - daves notes only so far (9 decks)

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