endocrine regulation: insulin secretion

Question 1

where else can you find the GLUT 2 transporter and why is this important

Answer 1

in the B cells in the islet. present all the time to detect changes in glucose levels.

Question 2

where is the pancreas located and what does it do

Answer 2

the pancreas lies along the small intestine. it has an exocrine function- secretes enzymes that move to the small intestine where it will break away the contents.

Question 3

what controls glucose in the pancreas and what do they contain

Answer 3

langerhan islets. they have alpha and beta cells which control glucose levels.

Question 4

how many islets of langerhans do we have

Answer 4

we have 3 million langerhan islets dotted around the pancreas.

Question 5

how long are langerhan cells and what are they composed of

Answer 5

they are a few microns in diameter and composed of endocrine cells. MAJORITY are beta cells.

Question 6

what do Beta cells do

Answer 6

they detect changes in glucose levels but also amino acids and hormones which will then dictate if insulin levels need to increase or decrease to regulate blood glucose levels.

Question 7

what makes beta cells unique to other cells when glucose enters the cell

Answer 7

while it also metabolises (goes in the mitochondria to gerenate ATP), unlike other cells where it simply uses the ATP, beta cells DETECT these changes to understand changes in glucose.

Question 8

how does the beta cell detect changes in ATP levels

Answer 8

Katp channel closure. this means its potassium channel that is sensitive to ATP. it detects this because its internal surface will sense it and close.

Question 9

what will happen to the cell when the potassium channel closes

Answer 9

because potassium is negative, closing it will make the cell move more positive. In reality, if there is nothing else coming it, the cell will stay the same but it is believed that there is another factor (like the sodium channel in neutrons) that make it move positive.

Question 10

what is the purpose of voltage dependent calcium channel (VDCC)

Answer 10

main conductor activated when the cell becomes more positive (more 40M)

Question 11

what happens when the voltage dependent calcium channel opens up

Answer 11

cytosolic calcium will go in the cell RAPIDLY and trigger diffusion of insulin containing granules with the cell membrane (exocytosis)

Question 12

how exactly does insulin come out of the beta cell

Answer 12

through exocytosis. The membrane bound capsule will fuse with the cell membrane and release insulin- for every one cell there is 9000 granules

Question 13

how does elevated calcium levels in the beta cell get detected

Answer 13

its the machinery linked with diffusion that can detect changes in calcium levels. its a mechanical process.

Question 14

what are the principles involved in the beta cell function

Answer 14

1. glucose enters GLUT 2 transporter
2. glucose goes into the mitochondria to be metabolised and make ATP
3. increase in ATP levels
4. closing of KATP voltage channel
5. depolarisation (making the cell more positive)
6. calcium voltage channels open and get activated
7. calcium enters the cell
8. this triggers the release of insulin granules by binding to the membrane and undergoing exocytosis.

Question 15

do calcium channels stay open or close in the beta cells

Answer 15

the calcium channels go up and down. we don’t understand the reasoning behind this.

Question 16

does the change happen instantly in the beta cell

Answer 16

no. it takes a bit of time with ATP levels increasing and potassium activity going down.

Question 17

what happens when you gust keep putting glucose in beta cells

Answer 17

after a while, the voltage will settle into a weird pattern. this could be because of hyper-repolarisation that occurs when calcium is activated.

Question 18

what is a hormone that can impact insulin secretion

Answer 18

GLP 1

Question 19

how and where is GLP 1 secreted

Answer 19

GLP 1 is secreted by cells lining the gut (small intestine) when they notice smth is in it. it simply goes into the circulation

Question 20

how does GLP 1 impact beta cells

Answer 20

it activates the receptor. this leads to an increase in cAMP. this impacts potassium channels, calcium channels and exocytosis.

Question 20

why is the hormone GLP 1 useless by itself

Answer 20

even though it activates a cascade or reactions, it cannot lead to the secretion of insulin on its own. mixed with glucose however, it allows the glucose to have a much bigger effect.

Question 21

how does GLP1 elevate glucose response

Answer 21

it primes the system. it responds to the content of the gut before is been digested and before glucose is broken down and brought into the body.

Question 22

what is the difference between between type 1 and type 2 diabetes

Answer 22

type 1 diabetes: almost no beta cells.

Question 23

how do you treat type 1 diabetes

Answer 23

you can use insulin injections to regulate it but those with severe type 1 diabetes need to undergo islet transplant. another is T1D- monitor that will read your glucose levels. helps to know how much insulin you need to maintain homeostasis.

Question 24

what is the purpose of alpha cells in islets

Answer 24

they produce glucagon

Question 25

what is the total age for getting type 1 diabetes

Answer 25

12 years old. it is very difficult to diagnose this. they often have a ketoacidosis (life threatening condition that risk them getting coma)

Question 25

what are the symptoms for type 1 diabetes

Answer 25

fatigue, weight loss, frequent urination- the higher glucose from eating creates an osmotic effect which increases water volume in your kidneys andtherefyor excessive thirst.

Question 26

how is type 1 diabetes and autoimmune disease

Answer 26

the body recognises beta cells as foreign. you will generate auto antibodies (against normal proteins in the body). this is the first development eg. GAD. secondly, after a few years, the immune system triggers T cells which specifically target B cells. this takes about 2-3 years.

Question 27

what is type 2 diabetes.

Answer 27

they have a deficit in insulin secretion.

Question 28

what is the purpose of GLP 1 in type 2 diabetes

Answer 28

adding GLP 1 in the beta cell will increase insulin again. this is what lead to the creation of ozempic

Question 29

symptoms of type 2 diabetes

Answer 29

Slow healing wounds Constant hunger Frequent urination Blurred vision Unexplained weight loss Numbness of hands and feet

Question 30

how does the types of diabetes make someone look

Answer 30

type 1 diabetes makes someone very thing while type 2 usually leads to obesity.

Question 31

levels of endogenous insulin In type 1 and type 2

Answer 31

type 1: low or absent type 2: normal or decreased amount.