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Physiology > Endocrine Pancreas and Carb Metabolism > Flashcards

Endocrine Pancreas and Carb Metabolism Flashcards

1
Q

Active transport of glucose

A

Occurs in the intestine and kidney

- co transport via Na/glucose

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2
Q

Passive transport of glucose

A
  • GLUT1: fetal tissues, erythrocytes
  • GLUT2: renal tubular cells, liver, beta cells
  • GLUT3: neruons –> diffusion with high affinity, even at low bg concentrations
  • GLUT4: insulin-regulated
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3
Q

Insulin-regulated glucose transport

A

Present in:

  • adipose
  • muscle
  • heart
  • -> inserts into membrane when activated by insulin
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4
Q

GLUT4 is not present in what tissues?

A
  • brain

- liver

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5
Q

Secretions of the endocrine pancreas

A

Interstitial fluid –> capillaries –> portal vein –> liver –> rest of the body

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6
Q

Insulin structure

A

Polypeptide

- C peptide: connecting peptide, secreted with insulin and directs fold of insulin

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7
Q

_____ can be used as a marker for endogenous insulin

A

C-peptide

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8
Q

Insulin structure variations

A
  • dogs: 1 amino acid (same as pigs!)
  • cats: 4 amino acids
  • horse: 2 amino acids
  • cow: 3 amino acids
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9
Q

Insulin is stored in ______

A

Secretory granules

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10
Q

Insulin in the blood

A

Circulates mostly unbound

  • half life in plasma: 6 min
  • mostly cleared within 10-15 min
  • degraded by insulinase in liver
  • allows rapid turn on/off of insulin functions
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11
Q

Insulin is ______

A

Anabolic

  • decreases bg
  • facilitates tissue uptake of glucose, amino acids, fatty acids, K, Mg, P
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12
Q

Insulin stimulates _____

A
  • glycogen synthesis
  • lipogenesis
  • protein synthesis and storage
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13
Q

Insulin inhibits ______

A
  • glycogenolysis
  • lipolysis
  • protein catabolism
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14
Q

Insulin receptor binding

A

Results within seconds!!

  • 80% of body’s cells increase glucose uptake (muscle, adipose, NOT most neurons)
  • immediate phosphorylation of glucose
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15
Q

Insulin helps transport glucose into the cell, ________ blood glucose

A

Decreasing

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16
Q

Glucose uptake via GLUT4

A

Insulin binding –> receptor activation

- translocation of intracellular vesicles with GLUT4 to cell membrane to facilitate glucose uptake into cells

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17
Q

What happens when insulin is no longer available?

A

Vesicles separate from cell membrane within 3-5 min and move back inside cell until needed again

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18
Q

Insulin is a requirement for glucose transport in all cells in the body, EXCEPT

A
  • neurons
  • intestinal epithelium
  • renal tubular epithelium
  • liver
  • RBC
  • leukocytes
  • beta cells
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19
Q

Insulin binding increases cell membrane permeability to

A
  • amino acids
  • K
  • P
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20
Q

Slower insulin effect

A

10-15 minutes

  • decrease or increase activity level of intracellular enzymes
  • continues for hours to days
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21
Q

Treatment of DKA with IV insulin

A
  • decreases K in blood
  • decreases P in blood
  • could lead to hemolysis and death
22
Q

Muscle in the presence of insulin

A
  • absorbs glucose for immediate energy

- synthesizes glycogen for use later

23
Q

Liver in the presence of insulin

A
  • stimulates glycogenesis (glycogen synthesis)

- inhibits glycogenolysis (glycogen breakdown)

24
Q

In the absence of insulin (between meals)

A
  • only slightly permeable to glucose

- muscle is dependent on FAs for energy

25
Q

In the presence of insulin (post-prandial)

A
  • high insulin, bg concentration

- insulin increases permeability to glucose

26
Q

____ is the preferential energy source during exercise

A

Glucose

27
Q

Effects of insulin on liver carbs

A

Promotes glucose storage in the form of glycogen

28
Q

Insulin ______ glucose uptake and retention

A

Enhances

  • increases activity of glucokinase (hexokinase)
  • decreases activity of phosphatase (would release glucose)
29
Q

Insulin _____ glycogen synthesis enzymes

A

Activates

  • increases glycogen synthase
  • enzyme adds glucose to glycogen polymers
30
Q

Insulin ______ breakdown of glycogen

A

Inhibits

  • decreases activity of liver phosphorylase
  • enzyme causes hepatic glycogen breakdown to glucose
31
Q

Liver in the absence of insulin (fasting)

A

Releases glucose into the circulating blood

  • decreases bg = decreased pancreatic insulin secretion
  • effects of insulin on glucose uptake and glycogen storage is reversed
32
Q

Glycogen breakdown

A

Phosphorylase activation
- splits glucose from glycogen
Glucose phosphatase activated (inhibited by insulin)
- allows free glucose to diffuse into blood

33
Q

Insulin is not present when ________

A

BG is low

34
Q

Glucose is the primary energy source in the _____

A

Brain

  • insulin has little effect on uptake/use of glucose in the brain
  • critical to maintain BG above a certain level
35
Q

Promotion of fat synthesis and storage by insulin

A
  • carb excess = promotion of FA synthesis in hepatocytes
  • promotes FA transport to and storage in adipose tissue
  • inhibits lipolysis (lipid breakdown)
36
Q

Insulin ____ hepatic glucose uptake

A

Increases

  • increase in hepatic glycogen leads to inhibition of further synthesis
  • glucose converted into substrates for FA synthesis via insulin
37
Q

Insulin ______ lipoprotein lipase

A

Activates

  • splits triglycerides into FA and glycerol
  • allows storage of TG in adipose tissue!
38
Q

Insulin ____ hormone-sensitive lipase

A

Inhibits

  • enzyme causes hydrolysis of TG stored in fat cells
  • releases FA from adipose into blood
39
Q

Insulin deficiency effect on lipids

A

Causes lipolysis!

  • hormone sensitive lipase activation
  • hydrolysis of stored TG = release of FA and glycerol into blood –> ketone formation in liver –> conversion of some FA into phospholipids and cholesterol
40
Q

Insulin ______ protein synthesis and storage

A

Promotes

  • stimulates transport of amino acids into cells, increasing translation of mRNA
  • inhibits protein catabolism
  • decreases hepatic gluconeogenesis
41
Q

Hypoglycemia

A

Brain depends upon a constant blood glucose concentration for optimal function

42
Q

Hyperglycemia

A

Causes decreased osmotic pressure and cellular dehydration

  • loss of glucose in urine results in osmotic diuresis and dehydration
  • damage to blood vessels and nerves over time (humans)
43
Q

The _____ is the primary regulator of insulin release

A

Blood glucose

  • glucose enters beta cells via GLUT 2 (non-insulin dependent)
  • rate of glucose entry controls exocytosis of insulin vesicles
44
Q

High BG = ____ insulin secretion

A

Increase

45
Q

Low BG = ____ insulin secretion

A

Decrease

46
Q

Stimuli of insulin secretion

A
  • increased blood amino acids
  • increased blood FAs
  • GI hormones
  • parasympathetic stimulation
  • GH, cortisol, glucagon, etc
47
Q

Inhibition of insulin release

A
  • somatostatin
  • sympathetic activity
  • fasting
48
Q

Glucagon function

A

Anti-insulin/diabetogenic

  • rapid acting
  • hepatic glycogenolysis
  • hepatic glucogenesis (amino acid mobilization)
  • lipolysis
49
Q

Glucagon regulation in response to glucose

A
  • decrease glucose = increased glucagon secretion

- increase glucose = decreased glucagon secretion

50
Q

Amino acids ____ glucagon secretion

A

Stimulate

  • same as insulin!!
  • for gluconeogenesis

Physiology (33 decks)

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