Homeostasis: Blood Glucose Control Flashcards
What is homeostasis?
Maintaining a stable internal environment in response to external and internal chnges using physiological control systems.
Why a maintaining a stable body temperature important?
If the temperature is too low, the enzymes of the body will have less energy, meaning they will move slower, and there will be less frequent collisions, which leads to the formation of an enzyme-substrate complex. This means the rate of metabolic reactions will decrease. If the temperature is too high, the hydrogen bonds in the enzymes will break, causing their tertiary structure to change and the shape of the active site to change. This means no more enzyme-substrate complexes will form, and the rate of metabolic reaction will decrease.
Why is maintaining the blood pH important?
If it becomes too acidic or alkali, the ionic bonds in the enzymes will break, causing its tertiary structure to change and the shape of the active site to change. This means no more enzyme-substrate complexes will form, and the rate of metabolic reaction will decrease.
Why is maintaing the blood glucose concentration important?
- If the blood concentration is too low there will be less oxygen available for respiration. This means the rate of respiration will decrease. The water potential in the blood will increase and be higher compared to the cells meaning water will move into the cell via osmosis. This causes them to expand and burst.
- If it is too high the water potential of the blood will decrease and be low compared to the water potential inside the cells. This will cause water to move out of the cell and shrink.
What is a negative feedback system?
A change in the normal levels brings about a response that reduces the effect of the change.
What is a positive feedback system?
A change in the normal levels brings about a response that amplifies the effect of the change.
What causes the blood glucose levels to decrease?
Exercise increases the rate of respiration meaning more oxygen is used up.
What causes the blood glucose levels to increase?
The digestion of carbohydrates and the absorption of the products causes the blood glucose levels to rise.
What is glycogenesis?
The synthesis of glycogen from glucose in muscle and liver cells.
What is glycogenolysis?
The breakdown of glycogen to release glucose in the liver cells.
What is glyconeogenesis?
The conversion of glycerol, fatty acids and amino acids into glucose in liver cells.
Describe what happens when the blood glucose levels rise?
- The beta cells detect the increase in blood glucose levels and secrete insulin.
- The insulin binds to the receptors on the cell membrane of the liver and muscle cells.
- This causes the ion channels to bind to the cell membranes of the cells.
- This allows glucose to move into the cells via facilitated diffusion.
- Insulin also triggers glucogenesis in the liver and muscle cells.
Describe what happens when the blood glucose levels decrease?
- The alpha cells detect the decrease in blood glucose levels and secrete glucagon.
- The glucagon binds to receptors on the cell membrane of liver cells and activates enzymes involved in glycogenolysis and glucogeneogenesis.
- Also, the adrenal glands release adrenaline, which binds to receptors on the cell membrane of the liver cells. This activates enzymes involved in glycogenolysis.
Describe the second messenger model for the action of glucagon and adrenaline?
- The hormones bind to the receptors on the cell membrane of the liver cells.
- This activates adenylate cyclase which converts ATP into cAMP.
- The cAMP activates another hormone called protein kinase A.
- Protein kinase A activates a cascade of reactions that result in glycogen being hydrolysed into glucose.
What causes Type 1 diabetes?
An autoimmune response leads to the destruction of the beta cells. This means they can no longer produce insulin, which means the blood glucose levels can’t be lowered and remain too high.
What is the treatment for type 1 diabetes?
Regular insulin injections and regulating carbohydrate intake.
What causes Type 2 diabetes?
The receptors in the liver and muscle cells are less sensitive to insulin. This means glycogenesis and glucose uptake do not increase in response to high blood glucose levels.
What is the treatment for type 2 diabetes?
- Improving diet: Eating a diet lower in sugar, salt and saturated fats and higher in fibre, fruits and vegetables.
- Regular exercise.
