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TMS exam > 1 - insulin secretion > Flashcards

1 - insulin secretion Flashcards

1
Q

normal blood glucose conc.

A

4-7mmol

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2
Q

what secretes insulin

A

pancreas

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3
Q

role of alpha cells

A

glucagon production

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4
Q

role of beta cells

A

insulin production

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5
Q

effect of eating on insulin levels

A

increase insulin conc. to keep blood glucose conc. within tight range

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6
Q

exocrine/endocrine parts of pancreas

A

pancreas is mainly exocrine

however islets of langerhans are endocrine

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7
Q

which 3 tissues does insulin act on to lower blood glucose

A

liver
muscle
adipose

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8
Q

effect of insulin on liver tissue

A

prevents glucose production

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9
Q

effect of insulin on muscle tissue

A

increases glucose uptake

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10
Q

effect of insulin on adipose tissue

A

prevents lipolysis

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11
Q

role of GLUT4 in muscle/adipose tissue

A

translocates to plasma membrane so more glucose can enter

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12
Q

what is glucagon

A

counter regulatory hormone to insulin

prevents hypoglycemia

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13
Q

action of glucagon on liver

A

decreases glycogen levels –> inhibits glycolysis and glycogenesis

increases glucose levels –> stimulates glucogenesis and glycogenolysis

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14
Q

3 lifestyle effects on blood sugar

A

exercise
illness
stress

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15
Q

how does stress effect blood sugar

A

parasympathetic nervous system increases insulin therefore decreases blood glucose

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16
Q

where is insulin stored

A

granule cells in cytoplasm of beta cells

17
Q

response of insulin to glucose

A

2 phases:

1st - immediate/rapid high peak of insulin
2nd - lower level sustained release of insulin

18
Q

glucagon receptors in liver

A

GPCR

glucagon binds and increases cAMP and PKA

19
Q

process of nutrient stimulated insulin secretion

A

increased blood glucose

detected by beta cells and taken up via up-regulated GLUT2 (facilitated diffusion down conc. gradient)

glycolysis:
glucose metabolised by glucokinase
increased ATP

ATP-sensitive K+ channels close –> membrane depolarises

voltage-gated Ca2+ channels open –> intracellular Ca2+ conc. increases

granules fuse with membrane and release insulin by exocytosis

20
Q

importance of fatty acids on nutrient stimulated insulin secretion

A

also metabolised in the krebs cycle
therefore more ATP produced
more K+channels close

21
Q

role of GPR40 receptor

A

GPCR fatty acid receptor
acts as a nutrient sensor
binds to free fatty acids
activates pathways to increase intracellular Ca2+

22
Q

which cells contain glucose instead of hexokinase IV

A

beta cells

23
Q

what is gluokinase

A

enzyme important for setting the threshold for insulin secretion in increased glucose

catalyses glucose phosphorylation

24
Q

phosphorylated glucose =

A

glucose-6-phosphate

25
Q

how is glucokinase different from hexokinase IV

A

it has low affinity for glucose therefore the glucose conc. has to be very high
it is not inhibited by the substrate

26
Q

properties of beta cells

A

GLUT2 transporter (low affinity for glucose)
vascularised islets for good blood supply
controlled number
highly specialised with unique transcription factors

27
Q

transcription factors specific to beta cells

A

PDX-1
NeuroD1
Nkx6

28
Q

GLUT2 adaptations

A

high capacity for glucose
low affinity for glucose

acts as a glucose “sensor”

29
Q

process of insulin uptake into cells

A

insulin binds to tyrosine kinase receptor
RTK transautophosphorylates and dimerises

IRS-1 signals to intracellular pathways

PIP2 –> PIP3
(recruits Akt kinase)

PDK-1 and PKB cause GLUT4 vesicles to move to membrane and uptake glucose

30
Q

role of IRS-1

insulin receptor substrate

A

signalling adaptor protein

signals from insulin/IGF-1 to intracellular signalling pathways such as PI3K/Erk/MAPK

phosphorylation by RTK produces binding sites via SH2 domains

31
Q

process of glucagon secretion

at low glucose conc.

A 
glucose cleaves GLUT1 transporter
K+/ATP channel closes
membrane depolarises
voltage-gated Ca2+ channels open --> increased intracellular Ca2+
glucagon secreted from vesicles
32
Q

process of glucagon uptake

A

G-alpha-s
–> adenyl cyclase –> cAMP –> pKA

phosphorylation by glycogen phosphorylase

  • -> glucose-1-phosphate
  • -> glucose-6-phosphate

glycogenolysis

33
Q

role of amino acids in insulin secretion

A

enter straight into krebs cycle for metabolism

34
Q

GLP-1

A

incretin

released from gut
acts on Beta cells to increase insulin secretion and decrease blood sugar
2nd messenger = cAMP

35
Q

how does parasympathetic NS effects glucose conc

A

cephalic stage of digestion stimulates insulin secretion

TMS exam (22 decks)

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