Control of Blood Glucose Flashcards
How is glucose transported in the blood?
Attached to haemoglobin on red blood cells
What are normal blood glucose levels?
4-8 mol/|L or 70-100mg/dL
What is hyperglycaemia?
to much glucose so its present in urine
What is hypoglycaemia?
to little glucose in the blood
What are 4 glucose metabolism mechanisms?
- Glycolysis
- Glycogenesis
- Glycogenolysis
- Gluconeogenesis
Describe the role of insulin release
Stimulates hepatocytes and skeletal muscle cells to synthesis glycogen
Describe the role of glycagen release
Stored in hepatocytes broken down to release glucose
Describe the absorptive state
Ingested nutrients entering the blood - effects of insulin dominate
Describe the post absorptive state
Absorption in small intestine nearly complete, blood glucose levels decrease
-main metabolic challenge to maintain normal blood glucose levels for red blood cells and neurones
Describe the effect of blood glucose increase
Insulin secretion increase
Describe the effect of blood glucose decrease
Glucagon levels increase
Describe the exocrine gland
Secretes enzymes to breakdown the proteins, lipids, carbohydrates and nucleic acid in food
Describe endocrine gland
Secretes hormones: insulin and glucagon to control blood sugar levels throughout the day
-islet of langerhan- alpha cell, beta cell and delta cell (secretes somatostatin)
How does insulin secretion constantly adjust to achieve homeostatic maintenance?
- lipid metabolism
- cell growth
- protein synthesis
What does the insulin signal transduction cascade result in?
Hexokinase activation so glucose is phosphorylated, glycolysis is inhibited
Describe the insulin release transporter mechanism
- Glucose enters beta cells is metabolised via glycolysis and Krebs cycle
- Metabolism causes high rates of ATP
- Increase in intracellular ATP: ADP ratios closes the ATP sensitive K+ channels. Prevents K+ from leaving cell by facilitated diffusion leading to build up of intracellular K+ ions. Inside becomes less negative therefore depolarisation
- Voltage gated Ca2+ ion channels open and Ca2+ move in via facilitated diffusion
- Increase in Ca2+ in cytoplasm causes insulin release into blood stored in extracellular secretory vesicles
Describe glucagon
Peptide hormone
Secreted from alpha cells of pancreas in response to low blood glucose levels and sympathetic ANS activation in exertion
Describe Amylin
Co-secreted with insulin from beta cells in ratio 100:1
Has a role in glycemic regulation by slowing gastric emptying and promoting satiety thereby preventing post meal spikes in blood glucose
Describe the glucose response in fight/flight
Extra glucose required
- adrenal medulla secretes increased levels of adrenaline
- adrenaline inhibits insulin and promotes breakdown of glycogen to glucose
What are three glucocorticoids?
And describe the role
- Cortisol
- Corticosterone
- Cortisone
Secretion under negative feedback system
low levels cause adrenocorticotropic hormone, helps provide energy burst to deal with stress
Describe diabetes and three key symptoms
Persistent hyperglycaemia Decrease in life experience -Tiredness -Polydipsia -Polyuria
What is the lifespan of a red blood cell?
120 days
Describe the glucose tolerance test
Measures how well body cells are able to absorb glucose after consumption
- 2 hour 75gram oral glucose test
- Fasting for 8-12 hours previous
describe the HbA1c Blood test
Amount of glucose combines with Hb total amount of sugar that is in the body system
-Glycolated haemoglobin
-Reflects average blood glucose levels over duration of 8-12 weeks lifespan of red blood cells
If HbA1c < 42mmol/L = normal
HbA1c > 47mmol/L = diabetic
