physiology of pancreas + insulin secretion (see notes!)

Question 1

does insulin increase more post oral glucose dose or post IV

Answer 1

Post oral

Question 2

what are the 4 parts of the pancreas

Answer 2

head, neck, body, tail

Question 3

where is the head of the pancreas situated

Answer 3

in the duodenal C loop, it also has an extension that wraps posteriorly around the sup. mesenteric vein+artery (uncinate process)

Question 4

what structure does the pancreas neck sit on

Answer 4

the portal vein

Question 5

what organ does the tail of the pancreas invaginate

Answer 5

the hilum of the spleen

Question 6

what artery runs along the top of the pancreas

Answer 6

splenic

Question 7

what arteries supply the pancreas

Answer 7

superior and inferior duodenal arteries

Question 8

where does the pancreas sit in relation to the stomach

Answer 8

behind it - it is a retroperitoneal organ

Question 9

what is the “lesser sac”

Answer 9

the space between the stomach and pancreas

Question 10

how can the lesser sac be accessed

Answer 10

via the epiplonic foramen

Question 11

what are the 2 glandular systems of the pancreas

Answer 11

endocrine and exocrine

Question 12

what does the exocrine system secrete and what process does it aid in

Answer 12

aids in digestions -> secretes enzymes and zymogens e.g. proteases, amylase, lipase

Question 13

what is a zymogen

Answer 13

an inactive enzyme precursor

Question 14

what does the endocrine system secrete

Answer 14

hormones -> these are secreted directly into the portal circulation

Question 15

what group of cells are the main players in the endocrine system

Answer 15

islets of Langerhans

Question 16

what are the 5 types of cells in islet of Langerhans and what do they secrete

Answer 16

α - glucagon
β - insulin
δ - somatostatin
PP - pancreas polypeptide
ε -ghrelin

Question 17

what kind of tumours form from mutations of islet cells

Answer 17

neuroendocrine

Question 18

what are the 3 methods by which islet cells communicate

Answer 18

1. humoural - cells within an islet can influence secretion of other cells as blood supply courses from the centre outward through the islet;
2. cell-cell - both gap and tight junctional structures connect islet cells with one another;
3. neural - symp/parasymp divisions regulate islet secretion

Question 19

what is metabolism

Answer 19

the flow of energy throughout the body

Question 20

what % of calorie consumption does the brain require

Answer 20

60-70%

Question 21

what 2 hormones mainly dictate what happens to glucose in the body

Answer 21

1. insulin (stores glucose)
2. glucagon (converts store back to glucose)

Question 22

what is the ideal blood glucose level

Answer 22

60-120mg/dL (4-6mm/L)

Question 23

above what level of blood glucose is hyperglycaemia

Answer 23

7 mm/L (126mg/dL)

Question 24

what diseases can arise from hyper glycaemia (general, 3)

Answer 24

eye, nerve, kidney disease -> aka diabetes

Question 25

3 reactions that can happen to glucose due to insulin release

Answer 25

1. glucose –(glycolysis)–> ATP
2. glucose <– (glycogenesis)–> glycogen (short term storage in liver/muscles)
3. glucose –(lipogensis)–> lipids/fats (long term storage in adipose)

Question 26

what hormone does insulin inhibit

Answer 26

glycogen

Question 27

3 ways glucagon converts substances

Answer 27

1. glycogen <–(glycogenolysis)–> glucose
2. amino acids <–(gluconeogenesis)–> glucose
3. fatty acids –(ketogenesis)–> ketone bodies

Question 28

what are ketone bodies used for

Answer 28

emergency energy supply when body goes into starvation mode -> can only be used by the heart + brain

Question 29

glucose binding to β cell -> insulin release pathway (draw this out!)

Answer 29

see notes

glucose binding to GLUT2 -> glucose endocytosed ->glucose kinase reacts (rate limiting step) -> glucose-6-phophate -> pyruvate (via glycolysis) -> krebs cycle (in mt.) -> oxidative phosphorylation -> ATP -> binds to ATP sensitive K+ Ch -> K+ can’t flow out along its gradient so cell becomes more positively charged -> -50mV threashold is reached allowing VG Ca2+ Chs to open -> Ca2+ influx-> insulin vesicle release -> insulin released into the blood

Question 30

what other substances can cause insulin secretion from β cells

Answer 30

amino acids, ketones, fatty acids (bypass glycolysis + link reaction) -> their action is enhanced by the presence of glucose tho

Question 31

what happens to the β cell when no glucose is present

Answer 31

ADP attaches to the the ATP sensitive K+ channel (as it is not being used in the formation of ATP) causing the channel to remain open -> k+ exits the cell and the cell becomes more negatively charged -> Ca2+ Ch does NOT open and so insulin cannot be released

Question 32

what is the effect of the parasympathetic system on insulin release

Answer 32

parapsymp signal (rest and digest) -> vagus stimulation -> Ach release -> insulin release is promoted

Question 33

what is MODY diabetes

Answer 33

a rare form of diabetes that occurs due to a glucose kinase mutation => G-6-P pathway is inhibited and ATP is not made => cell does not depolarise and so insulin is not released