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Endocrine System > The Endocrine Pancreas - Part 1 > Flashcards

The Endocrine Pancreas - Part 1 Flashcards

1
Q

What is body energy equal to?

A

Energy intake - energy output

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2
Q

What 2 hypothalamic centres determine energy intake by balance of activity?

A

Feeding centre - promotes feeling of hunger
Satiety centre - feeling of fullness by supressing feeding centre

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3
Q

What is the glucostatic theory?

A

Food intake is determined by blood glucose
As BG conc. increases then drive to eat decreases

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4
Q

What is lipostatic theory?

A

Food intake is determined by fat stores
As fat stores increase then drive to eat decreases
Leptin released by fat stores depresses feeding centres

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5
Q

What are the 3 categories of energy output?

A

Cellular work
Mechanical work - regulated voluntarily by skeletal muscle
Heat loss - counts for half of energy output

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6
Q

What are 3 elements of metabolism?

A

Extracting energy from nutrients in food
Storing that energy
Utilising that energy for work

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7
Q

What is the definition of metabolism?

A

Integration of all biochemical reactions in the body

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8
Q

What are anabolic and catabolic pathways?

A

Anabolic - build up, synthesis of large molecules from smaller for storage
Catabolic - break down, degradation of large molecules, releasing energy for work

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9
Q

What type of phase is the post absorptive phase?

A

Catabolic

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10
Q

What is an obligatory glucose utiliser?

A

Brain so BG conc. must be sufficient to supply brain even during fasted state
Failure causes hypoglycaemia

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11
Q

What is the normal range of BG levels?

A

4.2-6.3mM
Hypoglycaemia is under 3

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12
Q

What 2 endocrine hormones produced in pancreas maintain BG conc.?

A

Insulin and Glucagon

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13
Q

What is stimulated by insulin?

A

Lipogenesis
Glycogenesis
Metabolism in most tissues

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14
Q

What is stimulated by glucagon?

A

Glycogenolysis
Gluconeogenesis

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15
Q

Where are endocrine hormones released in pancreas?

A

Islets of Langerhans

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16
Q

What are the 4 types of islets cells?

A

Alpha
Beta
Delta
F cells

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17
Q

What do alpha islets cells produce?

A

Glucagon

18
Q

What do beta islets cells produce?

A

Insulin

19
Q

What do delta islets cells produce?

A

Somatostatin

20
Q

What do F islets cells produce?

A

Pancreatic polypeptide

21
Q

What happens if there is more insulin than glucagon?

A

Glucose taken up by cells from plasma lowering BG conc.
Increases glucose oxidation, glycogen synthesis, fat synthesis and protein synthesis

22
Q

Describe insulin

A

Peptide hormone
Stimulates glucose uptake by cells
Only hormone which lower BG conc.

23
Q

How is insulin synthesised and secreted?

A

Large preprohormone - pre-proinsulin which converted to proinsulin in the ER
Packaged as granules in secretory vesicles
Cleaved again to give insulin and C peptide
Stored till activated B cell

24
Q

What stimulates release of insulin?

A

Mainly blood glucose conc.
Amino acids

25
Q

How is glucose stored?

A

Mainly energy source in absorptive state
Excess stored as glycogen in liver and muscle
And as TAG in liver and adipose tissue

26
Q

What is excess amino acids and fatty acids stored as?

A

Aa - converted to fat
FA - triglycerides in adipose tissue and liver

27
Q

Describe the mechanism of control of insulin secretion by conc. of BG

A

Glucose is abundant so enters cells through GLUT and metabolism increases which increases ATP within cells
Katp channels to close - intracellular K conc. rises so depolarises cell
Voltage gated Ca channels open - trigger insulin vesicle exocytosis

28
Q

Describe low BG conc. and insulin secretion

A

Katp channels are open so K flows out of cells causing hyperpolarisation
Voltage gated Ca channels remain closed and insulin not secreted

29
Q

What is the primary action of insulin?

A

Binds to tyrosine kinase receptors on cell membrane of insulin dependant tissues to increase glucose uptake
In muscles and adipose tissue - stimulates specific GLUT4 which reside in cytoplasm

30
Q

What happens when GLUT4 is stimulated in muscle and adipose tissue?

A

Migrates to membrane and is able to transport glucose
When stimulation by insulin stops then GLUT4 return to cytoplasm pool

31
Q

What tissues are insulin dependant?

A

Muscles and fat

32
Q

What GLUT transporters are not insulin dependant?

A

GLUT1 - basal glucose uptake in tissues
GLUT2 - similar
GLUT3 - b cells of pancreas and liver

33
Q

Describe liver and glucose uptake

A

GLUT2 transporters and is insulin independent
Enters down conc. gradient
Glucose transport into hepatocytes is affected by insulin status

34
Q

What happens in fed state in liver and glucose uptake?

A

Liver takes up glucose as insulin activates hexokinase which lowers glucose conc. in cells creating a gradient so movement in cells can happen

35
Q

What happens in fasted state in liver and glucose transport?

A

Liver synthesises glucose via glycogenolysis and gluconeogenesis
Increases glucose conc. in cells so gradient favours glucose movement out of cell

36
Q

What are some of the the additional actions of insulin?

A

Increase glycogen synthesis and inhibits glycogen phosphorylase
Promotes protein synthesis and inhibits proteolysis
Increases lipogenesis and inhibits lipolysis
Inhibits enzymes of gluconeogenesis
Permissive effect on GH
Promotes K ion entry stimulating NaKATPase

37
Q

What happens when insulin binds to tyrosine kinase receptor?

A

Receptor phosphorylates insulin receptor substrates (IRS)
Second messenger pathways alter protein synthesis and existing proteins
Membrane transport or cell metabolism changed

38
Q

What stimulates insulin release?

A

Increased BG conc.
Increased aa conc. in plasma
Glucagon
Other hormones controlling GI secretion

39
Q

What stimuli inhibit insulin release?

A

Low BG conc.
Somatostatin
Sympathetic alpha-2 effects
Stress - hypoxia

40
Q

Is IV or oral glucose has more insulin response?

A

Oral as increases insulin by direct effect in B cells and vagal stimulation of B cells plus incretin effects

Endocrine System (23 decks)

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