eLFH - Metabolism Physiology Part 2 Flashcards
Normal blood glucose range
4 - 8 mmol/L
Hormones with role in decreasing blood glucose levels
Insulin
Hormones with role in increasing blood glucose levels
Glucagon (main one)
Catecholamines
Cortisol
Growth hormone
Somatostatin
Thyroxine
Oestrogen / Progesterone
Glycolysis definition + location
Process by which glucose is broken down to pyruvate to release energy
Occurs in all cells
Glycogenolysis definition + location
Process by which glycogen is broken down to glucose
Occurs mainly in liver and muscles
Glycogenesis definition + location
Process by which glucose is converted to glycogen
Occurs mainly in liver and muscles
Gluconeogenesis definition + location
Process by which glucose is synthesised from non-carbohydrate sources (E.g. amino acids, glycerol)
Occurs mainly in liver and kidneys
Structure of insulin
51 amino acids
2 peptide chains linked by disulphide bridges
Where is insulin secreted from
Beta cells in islets of Langerhans in pancreas
Action of Insulin at receptor level
Acts via tyrosine kinase receptors on many different cell types
Results in translocation of glucose transporters to the cell membrane to increase glucose uptake
Actions as a result of insulin release
Increases:
Glucose uptake
Glycogen synthesis
Protein synthesis
Fat synthesis
Potassium uptake by cells
Decreases:
Gluconeogenesis in liver
Structure of Glucagon
29 amino acids
Single polypeptide chain
Where is Glucagon secreted from
Alpha cells in Islets of Langerhans in pancreas
Action of Glucagon at receptor level
Acts on liver via G-protein linked receptors
Actions as a result of glucagon release
Increases:
Glycogenolysis in liver
Gluconeogenesis
Lipolysis including ketoacid formation
Stimulates release of insulin, growth hormone and somatostatin
Actions of Glucagon on cardiovascular system
Causes non-adrenergic inotropic and chronotropic effects on heart
Hence use in Beta blocker overdose
Factors which increase insulin levels
Raised glucose
Glucagon (paracrine effect)
Drugs:
Phosphodiesterase inhibitors
Sulphonylureas
Factors which decrease glucagon levels
Raised glucose
Raised ketoacids
Raised free fatty acids
Insulin
Factors which decrease insulin levels
Alpha 2 adrenoreceptor stimulation
Insulin (autoinhibition)
Drugs:
Diazoxide
Thiazide diuretics
Beta blockers
Diazoxide drug use
Persistent hypoglycaemia
Factors which increase glucagon levels
Low glucose
Beta 2 adrenoreceptor stimulation (e.g. stress, exercise)
Factors which inhibit both insulin and glucagon release
Insulin
Somatostatin
Factors which stimulate both insulin and glucagon release
Amino acids
Gastrointestinal hormones
Vagal stimulation
All above increase after a meal
Effect of catecholamines and sympathetic nervous system on blood glucose
Net increase in blood glucose by:
- Glycogenolysis
- GNG
- Lipolysis
- Inhibits insulin secretion via pancreatic alpha 2 receptors
- Stimulates glucagon secretion via pancreatic beta 2 receptors
Effect of cortisol on blood glucose
Net increase in blood glucose over hours to days by:
- GNG
- Protein breakdown
- Reduced glucose utilisation by cells
- Lipolysis
- Promotion of keto-adaptation
Effect of growth hormone on blood glucose
Net increase in blood glucose by catabolic actions:
- Glycogenolysis
- Lipolysis
- Promotion of keto-adaptation
Also has anabolic action of protein synthesis
Secretion of somatostatin
Released by pancreatic delta cells and the hypothalamus in response to high glucose, amino acids and fatty acids
Effect of somatostatin on blood glucose
Net increase in blood glucose by:
- Inhibits gut motility and secretion - makes food available over longer period of time
- Inhibits release of insulin and glucagon
Effect of thyroxine on blood glucose
Net increase in blood glucose by:
- Increases glucose absorption from gut
- Glycogenolysis
- GNG
Effect of oestrogen and progesterone on blood glucose
Net increase in blood glucose vis increased peripheral insulin resistance
Hence gestational diabetes
Effect of hypothermia on blood glucose
Increases glucose levels
