Pancreas structure and function

Question 1

Where the pancreas exactly found?

Answer 1

Upper part of the abdomen, behind the stomach

Question 2

What two things does the pancreas secrete?

Answer 2

Hormones (its a glandular organ)
Enzymes (in digestion)

Question 3

How does pancreas fulfil its role as an exocrine gland?

Answer 3

Most of the pancreas is made up of exocrine glandular tissue
This tissue produces digestive enzymes such as amylase, lipase and proteas and an alkaline fluid known as pancreatic juice which are firstly secreted into ducts which eventually lead to the pancreatic duct.

From here they are released into the duodenum which is the top part of the small intestine -

Question 4

How does pancreas fulfil its role as an endocrine gland?

Answer 4

It is responsible for producing insulin and glucagon - two important hormones which the pancreas secretes directly into the bloodstream.

Question 5

Where is the endocrine tissue in the pancreas?
Name?

Answer 5

The pancreas is largely made up of exocrine tissue (known as pancreatic acini) - within this however, there are small regions of endocrine tissue called ISLETS OF LANGERHAMS - these cells are what produce insulin and glucagon.

Question 6

Name of exocrine tissue in the pancreas?
Difference in appearance between this and endocrine tissue in pancreas?

Answer 6

Pancreatic acini
This is darker stained in comparison to islets of langerhams (endocrine tissue) which is lighter stained.

Question 7

What are the two types of cells in the pancreas?
Their function?

Answer 7

Alpha cells - produce + secrete glucagon into the bloodstream
Beta cells - product secrete insulin into the bloodstream

Question 8

3 Differences between alpha cells and beta cells

Answer 8

1) Function - hormones they produce and secrete
2) Size - alpha cells are larger
3) Quantity of each - alpha cells are more numerous than beta cells within an islet.

Question 9

3 ways blood glucose concentration can increase:

Answer 9

1) Diet - eating carbohydrate-rich foods which is rich in starch - so it gets broken down into glucose which gets absorbed into the blood stream
2) Glycogenolysis - glycogen breaking down into glucose which increases blood glucose concentration
3) Gluconeogenesis - production of glucose from non-carbohydrate sources - for example, the liver makes glucose from glycerol and amino acids.

Question 10

2 ways blood glucose concentration can decrease:

Answer 10

1) Respiration - Body generates energy from glucose in order for muscles to contract.
2) Glycogenesis - production of glycogen from glucose - when blood glucose concentration is too high, excess glucose taken in through the diet and converted to glycogen which is stored in the liver.

Question 11

How many cells have insulin receptors in their body?
Any exceptions?

Answer 11

Virtually all cells have insulin receptors apart from red blood cells which don’t have insulin receptors

Question 12

How does insulin lower blood glucose concentration? (in regard to hormones + receptors)

Scientific terms.

Answer 12

When it binds to its glycoprotein receptor, it causes a change in the tertiary structure of the glucose transport protein channels.

This causes channels to open allowing more glucose to enter the cell. Insulin also activates enzymes within some cells to convert glucose into glycogen and fat.

Question 13

5 ways in which insulin helps to reduce blood glucose concentration?

Answer 13

1) Increasing the absorption/uptake of glucose in cells.
2) Increasing rate of glycogenesis- by making glycogen from glucose and storing it in liver/muscle cells.
3) Increasing the respiratory rate of cells - increasing cell’s need for glucose - higher uptake of glucose from blood.
4) Glucose to fat conversion.
5) Inhibiting release of glucagon from alpha cells in each islet.

Question 14

What happens to insulin after its done its job (after having bound to glycoprotien receptors…)?

Answer 14

It is broken down by enzymes in the cells of the liver.

Question 15

When does insulin excretion stop?

Answer 15

When the blood concentration returns back to the normal level.

Question 16

What cells in the body have glucagon receptors?

Answer 16

Only liver and fat cells

Question 17

How does glucagon increase blood glucose concentration?

Answer 17

1) Glycogenolysis - breaking down glycogen to secrete glucose
2) Gluconeogenesis - producing glucose from non-carbohydrate sources such as fats/proteins/glycerol in the liver.
3) Reducing amount of glucose absorbed by liver cells.

Question 18

Insulin and Glucagon are ________ hormones:

Answer 18

Antagonistic - do opposite responses/functions, WORK AGAINST EACH OTHER.

Question 19

Normal blood glucose level:

Answer 19

90 mg/100cm3 of blood

Question 20

How does insulin secretion occur in a B cell?
(Mechanism)

Answer 20

High blood glucose concentration is detected by B cells in pancreas and insulin is released.
MECHANISM:
1) As normal blood glucose levels increase, potassium ion channels in the plasma membrane of B cells open and potassium ions diffuse out of the cell.
2) When blood glucose concentration rises, glucose enters the cell by a glucose transporter which is the glucose transport protein channel.
3) Glucose is metabolised inside the mitochondria of the B cell, resulting in the production of ATP.
4) This ATP binds to potassium channels and causes them to close. These are known as ATP-sensitive potassium channels.
5) As potassium ions can no longer diffuse out of the cell, the potential difference reduces to around -30 mv and depolarisation occurs.
6) Depolarisation causes the voltage-gated calcium ion channels to open.
7) Calcium ions enter the cell and cause secretory vesicles to release the insulin they contain by exocytosis.

Question 21

What essentially is diabetes?

Answer 21

A condition where the pancreas either cannot produce insulin, or our body cells do not effectively respond to the insulin produced.

As such, high blood sugar (hyperglycaemia) is a common effect of uncontrolled diabetes

Question 22

Why is hyperglycaemia (high blood sugar) harmful to the body?

Answer 22

1) Serious damage to nerves (neuropathy) and blood vessels
E.g. High blood glucose erodes the myelin sheath that affects the pace at which the nerve/electrical impulse passes through.
2) Damage to kidney as well - since when filtering blood a lot of glucose reabsorbed - overworks kidney

Question 23

Type 1 diabetes:

How is it caused?

Answer 23

Patients B cells are unable to produce insulin.
In many cases, this condition arises as a result of an autoimmune response where the body’s own immune system attacks the B cells.

More genetic cause

Question 24

Type 2 diabetes:

How is it caused?

Answer 24

Patients cannot effectively use insulin and control their blood sugar levels - either the persons B cells do not produce ENOUGH insulin or it may be that their body cells do not respond properly to insulin.

This is often because the glycoprotein insulin receptor on the cell membrane does not work properly so cells lose their responsiveness to insulin.

More lifestyle related

Question 25

Type 1 diabetes: - treatment

Answer 25

1) Regular insulin injections/pumps - first work out blood glucose concentration by taking sample of blood from finger.and lets you know the does of insulin you need to inject.

Question 26

Why is it important insulin injections are carefully monitored?

Answer 26

Injecting too much insulin results in hypoglycaemia which is very low blood glucose concentration that can result in unconsciousness or death. The same consequenes for hyperglycaemia.

Question 27

Type 2 diabetes: - treatment

Answer 27

Regulate person's carbohydrate intake (changes to diet - low sugar) Exercise - lose weight if overweight Certain drugs that slow down rate at which body absorbs insulin from the small intestine.

Question 28

Where was insulin originally obtained from? Where is it obtained from now? Advantages of human insulin over animal insulin:

Answer 28

Pancreas of animals such as cows and pigs Once, human insulin structure was identified, it was since specifically made by genetically modified bacteria. Advantages: 1) Human insulin is produced in a pure form - less likely to cause allergic reactions 2) Insulin can be produced in much larger quantities. 3) Cheaper to produce 4) Ethical issues of animal rights overcome

Question 29

Pancreas transplants? What's the disadvantage of immunosuppresants?

Answer 29

They provide of way of essentially changing Beta cells that are no longer functional. It means you entirely fix the issue of diabetes, with no insulin injections having to be taken as well. The danger arises with immune system rejections - which is why immunosuppresants are required to be taken. Immunosuppressants increase the metabolic demand of B cells which eventually exhausts their ability to produce insulin.

Question 30

Stem cell therapy - where stem cells come from, ethical issues? is there an answer to these ethical issues?

Answer 30

For this, we will need totipotent stem cells (which can differentiate into any type of cell) - which means we will need to extract this stem cells from an embryo. There are ethical issues regarding this, the main one being a human life is lost, but then again, these are "spare embryos" (from infertility clinics or terminated pregnancies), and would usually be destroyed anyway.

Question 31

Advantages of stem cell therapy over current therapies? A MAJOR CON (barring ethical issues)

Answer 31

1) Donor availability is not an issue - stem cells produce an unlimited source of new beta cells. 2) reduced likelihood of rejection problems as embryonic stem cells are not usually rejected by the body. 3) No need for insulin injections - not time-efficient. CON: Potential for cancer - given that our own ability to control growth and differentiation in stem cells is limited.

Question 32

What actually is a fight or flight response? (in basic terms)

Answer 32

An instinctive response, where when a potentially dangerous situation is detected, the body automatically triggers a series of physical responses which are intended to make an organism fight for their life or run for life (in animals - hence the name).

Question 33

How is a fight or flight response carried out? (scientifically, with respect to nervous systems)

Answer 33

Once a threat is detected by the autonomic nervous system, the hypothamalus communicates with the sympathetic nervous system and the adrenal-cortical system. The sympathetic nervous system uses neuronal pathways to initiate body reactions whereas the adrenal-cortical system uses hormones in the bloodstream. The combined effects of both hormones and nerve impulses results in the fight or flight response.

Question 34

What exactly is the role of the sympathetic nervous system in the flight or fight response?

Answer 34

Sends out nerve impulses to glands and smooth muscles and tells the adrenall medulla to release adrenaline and noradrenaline into the bloodstream. increases heart rate.

Question 35

How does the adrenal cortex work in the flight or fight response? What is it controlled by? - how is it controlled like this?

Answer 35

This is referring to the adrenal cortex - controlled by hormones produced in the pituitary gland of the brain. The hypothamalus stimulates the pituitary gland to release ACTH (adrenocorticotropic hormone), which travels in the bloodstream, before reaching the adrenal cortex which stimulates it to release other hormones. Releases cortisol - in response to stress.

Question 36

Examples of physical responses in the fight or flight response:

Answer 36

HR increases - pump more oxygenated blood around the body Pupils dilate - to take in as much light as possible for better vision Arterioles in skin constrict - more blood to major muscle groups, brain, heart... Blood glucose level increases - increase respiration to provide energy for muscle contraction Smooth muscle of airways relaxes - allow more oxygen into lungs Non-essential systems such as the digestive system shut down - focus resources on emergency functions.

Question 37

How does adrenaline play a role in the flight and fight response?

Answer 37

Triggers liver cells to undergo glycogenolysis to break down glycogen into glucose - respiration rate can increase so more energy available for muscle contraction.

Question 38

What part of the brain initiates the fight or flight response?

Answer 38

Amygdala

Question 39

Detail the action of adrenaline:

Answer 39

1) When adrenaline binds to its complementary receptor, the enzyme adenylyl cyclase is activated. 2) Adenylyl cyclase triggers the conversion of ATP into cAMP (cyclic adenosine monophosphate) on the inner surface of the cell membrane in the cytoplasm. 3) Increase in the cAMP levels activates protein kinases (enzymes) which phosphorylate and hence activate other enzymes. Here, the enzymes which are activated trigger the conversion of glycogen into glucose.

Question 40

What is the second messenger model? Cascade effect?

Answer 40

Two messengers each of which are hormones Adrenaline is the first messenger and cAMP is the second messenger. One hormone can cause many cAMP molecules to form. Cascade effect: At each stage, number of molecules involved increases. E.g. Adrenaline (1 molecule) ---> cAMP (2 molecules) -------> Protein kinase enzymes (8 molecules).