Physiology 6 - Feedback control of glucose Flashcards
Why is the feedback control of plasma glucose so critical?
The brain is a “glucose obligate” tissue and stores little glycogenThe blood brain barrier makes the brain inaccessible to plasma fatty acids
When does hypoglycaemia occur?
When blood sugar levels fall below 4 mmol/L (if below 2.5 can cause confusion and coma)
What effect does chronic hyperglycaemia have on blood vessels?
Damages them
What hormones control [glucose]p in the absorptive and post-absorptive state (fed and between meals)? (2)
Insulin and glucagon (pancreas)
What hormones control [glucose]p in emergencies?
Glucagon (pancreas)
What hormones control [glucose]p during starvation? (2)
Cortisol (adrenal)Growth hormones (pituitary)
What type of cells make up the pancreatic islets of langerhans and what does each secrete?
A cells - glucagonB cells - insulinD cells - somatostatin
What ensues if the islets of langerhans are removed or destroyed?
Diabetes mellitus - lack of insulin or impaired cellular responses to insulin
Changes in glucose, insulin and glucagon levels during the absorptive state?
[Glucose]p rises[insulin]p rises[glucagon]p falls
What type of meal causes an increase in the amount of insulin released compared to there types of meals?
Carbohydrate rich meals
What does insulin do?Is insulin the hormone of the fed or hungry state?
Favours anabolismTherefore stimulates conversion of glucose into glycogen, fatty acids into triglycerides and amino acids into proteinFed-state
What does glucagon do?Is glucagon the hormones of the fed or hungry state?
Favours catabolismStimulates conversion of glycogen into glucose and triglycerides into fatty cardsHungry-state
How does insulin lower the plasma concentration of glucose? (2)
By stimulating the uptake of glucose from the blood into fat and muscle cellsActivating the enzyme in the liver and muscle which converts glucose into glycogen(insulin also promotes the incorporation of amino acids into protein in muscle and promotes lipogenesis in adipose tissue)
How does insulin promote glucose uptake into muscle and fat?
insulin causes glucose transporter proteins (GLUT4) to be inserted into the plasma membrane of muscle and dat cells from intracellular stores (when insulin levels drop off the transporters become internalised again)
What promotes the secretion of insulin? (5)
Increased glucoseIncreased amino acidsincreased parasympathetic activityIncreased glucagon (causes it to be produced and stored ready for release, not release)GIP (glucose-dependent insulinotropic peptide - hormone produced in small intestine)