The Endocrine Pancreas I and II

Question 1

Define the term ‘obligatory glucose utilising tissues’.

Answer 1

a

Question 2

Define the term ‘non-obligatory glucose utilising tissues’.

Answer 2

a

Question 3

Give examples of obligatory glucose utilising tissues.

Answer 3

a

Question 4

Give examples of non-obligatory glucose utilising tissues.

Answer 4

a

Question 5

State the range of plasma glucose that may be expected in normal resting subjects who have fasted overnight.

Answer 5

Normal range of [BG] = 4.2-6.3mM (80-120mg/dl)

5 mmoles useful to remember

Hypoglycaemia = [BG] < 3mM

Question 6

Describe the process by which insulin is released.

Answer 6

a

Question 7

Describe the process by which glucagon is released.

Answer 7

a

Question 8

Describe how the release of insulin impacts on the release of glucagon and vice versa.

Answer 8

a

Question 9

Describe the sites of action of insulin on blood glucose levels.

Answer 9

a

Question 10

Describe the mechanism of action of insulin on blood glucose levels.

Answer 10

a

Question 11

Describe the sites of action of glucagon on blood glucose levels.

Answer 11

a

Question 12

Describe the mechanism of action of glucagon on blood glucose levels.

Answer 12

a

Question 13

Describe how the release of glucagon impacts on the metabolism of fat and protein.

Answer 13

a

Question 14

Describe the interaction between insulin and the counter-regulatory hormone, glucagon.

Answer 14

a

Question 15

Describe the interaction between insulin and the counter-regulatory hormone, adrenaline.

Answer 15

a

Question 16

Describe the interaction between insulin and the counter-regulatory hormone, cortisol.

Answer 16

a

Question 17

Describe the interaction between insulin and the counter-regulatory hormone, GH.

Answer 17

a

Question 18

Describe how glucose metabolism can change in times of stress (exercise, starvation, diabetes).

Answer 18

a

Question 19

Compare and contrast Type 1 and Type 2 Diabetes Mellitus.

Answer 19

a

Question 20

Appreciate the aetiology and risk of diabetic ketoacidosis.

Answer 20

a

Question 21

Body energy = what?

Answer 21

Body energy = energy intake - energy output.

Question 22

What determines energy (food) intake?

Answer 22

Energy (food) intake is the determined by the balance of activity in two hypothalamic centres;

• Feeding centre: promotes feelings of hunger and drive to eat.
• Satiety centre: promotes feelings of fullness by suppressing the Feeding Centre.

Question 23

What control the activity of the feeding and satiety centres?

Answer 23

Activity in each is controlled by a complex balance of neural and chemical signals as well as the presence of nutrients in plasma.

Question 24

Describe glucostatic theory.

Answer 24

Food intake is determined by blood glucose: as [BG] increases, the drive to eat decreases (- feeding centre; + satiety centre).

Question 25

Describe lipostatic theory.

Answer 25

Food intake is determined by fat stores: as fat stores increase, the drive to eat decreases (- feeding centre; + satiety centre).

Leptin is a peptide hormone released by fat stores that depresses feeding activity.

Question 26

What disrupts both the glucostatic and lipostatic pathways?

Answer 26

Obesity.

Question 27

What does energy output describe?

Answer 27

All the processes we perform in order to stay alive, and those that we perform voluntarily, as well as the heat loss associated with these.

Question 28

Describe the 3 categories of energy output.

Answer 28

Cellular work – transporting molecules across membranes; growth and repair; storage of energy (e.g. fat, glycogen, ATP synthesis).

Mechanical work – movement, either on a large scale using muscle or intracellularly.

Heat loss – associated with cellular and mechanical work, accounts for half our energy output.

The only part of energy output we can regulate voluntarily is mechanical work done by skeletal muscle.

Question 29

Define metabolism.

Answer 29

Integration of all biochemical reactions in the body.

Question 30

Name the 3 elements of metabolism.

Answer 30

• Extracting energy from nutrients in food
• Storing that energy
• Utilising that energy for work

Question 31

Describe anabolic pathways.

Answer 31

Build Up. Net effect is synthesis of large molecules from smaller ones, usually for storage purposes.

Question 32

Describe catabolic pathways.

Answer 32

Break Down. Net effect is degradation of large molecules into smaller ones, releasing energy for work.

Question 33

State the meaning of the absorptive state and post-absorptive state.

Answer 33

After eating we enter an Absorptive State where ingested nutrients supply the energy needs of the body and excess is stored. This is an anabolic phase.

Between meals and overnight the pool of nutrients in the plasma decreases and we enter a Post-absorptive State (AKA Fasted State) where we rely on body stores to provide energy. This is a catabolic phase.

Question 34

Explain why the brain is an ‘obligatory glucose utiliser’.

Answer 34

Most cells can use fats, carbohydrates or protein for energy but the brain can only use glucose (except in extreme starvation). So in the post-absorptive state, even though no new carbohydrate is gained by the body, we MUST maintain blood glucose concentration [BG] sufficient to meet the brain’s requirements.

Failure to do so results in hypoglycaemia, which can lead to coma and death.

Question 35

How is blood glucose maintained?

Answer 35

BG is maintained by synthesising glucose from glycogen (glycogenolysis) or amino acids (gluconeogensis):

Question 36

Describe the exocrine and endocrine functions of the pancreas.

Answer 36

99% of the pancreas operates as an exocrine gland releasing enzymes and NaHCO3 via ducts into the alimentary canal to support digestion.

Only 1% of the pancreas has endocrine function. Its hormones are produced in the Islets of Langerhans.

Question 37

Describe the Islets of Langerhans, their cells and the hormones they produce.

Answer 37

The Islets of Langerhans are scattered throughout the pancreas, 1-2 million islets, each with a copious blood supply.

4 types of islet cells: a, b, d & F;

• a cells produce GLUCAGON
• b cells produce INSULIN
• c cells produce SOMATOSTATIN
• F cells produce pancreatic polypeptide (function not really known, may help control of nutrient absorption from GIT)

Question 38

Describe the balance of insulin and glucagon in the fed state.

Answer 38

Glucose taken up by cells from plasma ([BG] decreases).

Insulin dominates, causing;

• Increase in glucose/glycogen oxidation
• Increase in fat/protein synthesis

Question 39

Describe the balance of insulin and glucagon in the fasted state.

Answer 39

Glucose released into plasma from stores ([BG] increases).

Glucagon dominates, causing;

• Increase in glycogenolysis
• Increase in Gluconeogenesis
• Increase in ketogenesis