Pancreas (Physiology)

Question 1

Summarise the main factors affecting blood glucose concentration

Answer 1

Glucose lowering reactions

• Glucose uptake by cells.
• Glucose breakdown for energy.
• Glucose storage as glycogen.
• Glucose conversion to non-carbohydrates.

Glucose raising reactions

• Use of fatty acids for energy (glucose-sparing).
• Release of glucose from glycogen (glycogenolysis).
• Formation of glucose from non-carbohydrate sources (gluconeogenesis) and lactate.
• Transport of glucose from the liver into the blood.

Question 2

List the principal hormones of the endocrine pancreas

Answer 2

• Insulin
• Glucagon

Also involved in control of blood glucose:

• Catecholamines
• Growth hormone
• Glucocorticoids (cortisol is a permissive hormone - needs to be present for other hormones to work optimally).

Question 3

Describe the main roles of insulin in the regulation of glucose, amino acids and fat metabolism after a meal

Answer 3

• Stimulates cells to absorb glucose, fatty acids, and amino acids and to store or metabolise them, therefore lowering the level of blood glucose and other nutrients.
• Promotes the synthesis of glycogen, fat, and protein, therefore promoting the storage of of excess nutrients for later use and enhancing cellular growth and differentiation.
• It antagonises glucagon, therefore suppressing the use of already-stored fuels.
• Promotes glycogen synthesis in the liver.
• Increases the rate of conversion of amino acid to protein and inhibits protein degradation.

Question 4

State the role of glucagon in starvation

Answer 4

• A decrease in blood glucose levels stimulates alpha cells in the pancreas to secrete more glucagon.
• In the liver, an increase in glucagon secretion promotes gluconeogenesis and glycogenolysis, resulting in an increase in blood glucose levels.
• In adipose tissue, an increase in glucagon secretion promotes lipolysis which increases the levels of fatty acids in the blood and therefore exerting a glucose-sparing effect.
• Once the blood glucose levels have returned to normal, systemic homeostasis returns via a negative feedback mechanism which switches off the activation of alpha cells.

Question 5

List the effects of hypoglycaemia

Answer 5

Causes the brain to starve as more glucose than necessary is driven into other tissues. This can result in impaired cognitive function, unconsciousness, and death.