Homeostasis (Edexcel GCSE Combined Science: Biology): Flashcards
Exam code: 1SC0
1/330Still learning
Know0
Homeostasis
Was this flashcard helpful?
Cards in this collection (33)
Homeostasis
The maintenance of a constant internal environment.
Negative feedback
A control mechanism in which a change away from the set point triggers a response that returns conditions to the set point.
Why is homeostasis important?
Internal conditions must be kept within set limits so that reactions in body cells can function, allowing the organism to live.
Give three internal conditions that must be kept within set limits.
Temperature, blood pressure, water concentration and glucose concentration (any three).
What is meant by the 'set point' in homeostasis?
The ideal/normal level of a condition that negative feedback works to maintain.
In negative feedback, what happens if the level of something rises?
Control systems are switched on to reduce it again.
In negative feedback, what happens if the level of something falls?
Control systems are switched on to raise it again.
Why must diabetics control their glucose intake?
Because their body cannot regulate blood glucose for them.
What is the overall effect of negative feedback mechanisms on body conditions?
They keep conditions within a narrow range of what is considered 'normal'.
Homeostasis is the maintenance of a constant environment so that in body cells can function.
internal / reactions
Most homeostatic mechanisms are controlled by feedback, which returns conditions to the point.
negative / set
Insulin
A hormone produced by the pancreas that lowers blood glucose by stimulating cells to take up glucose from the blood.
Glycogen
A storage polymer of glucose made in liver and muscle cells.
Which organ monitors and controls blood glucose concentration?
The pancreas.
What happens to blood glucose after eating carbohydrate, and how does the pancreas respond?
Glucose enters the bloodstream and the concentration rises; the pancreas produces insulin to bring it back down.
How does insulin lower blood glucose concentration?
It stimulates cells (particularly liver and muscle cells) to take up glucose from the blood, where excess glucose is converted into glycogen for storage.
Why is too high a level of glucose in the blood dangerous?
Cells of the body can lose water by osmosis.
What does glucagon do when blood glucose concentration is too low? (Higher Tier Only)
It causes glycogen stored in liver and muscle cells to be converted into glucose, which is released into the blood.
Describe how insulin and glucagon control blood glucose by negative feedback. (Higher Tier Only)
When blood glucose rises, insulin stimulates liver and muscle cells to convert glucose into glycogen, lowering the level.
When blood glucose falls, glucagon stimulates liver and muscle cells to convert glycogen into glucose, raising the level.
What is the difference between glucagon and glycogen? (Higher Tier Only)
Glucagon is a hormone; glycogen is the polysaccharide that glucose is stored as.
When blood glucose is too high, the pancreas releases , which causes liver and muscle cells to store glucose as .
insulin / glycogen
When blood glucose falls too low, the pancreas releases , which converts glycogen back into . (Higher Tier Only)
glucagon / glucose
Type 1 diabetes
A disorder in which the pancreas fails to produce sufficient insulin to control blood glucose levels.
Type 2 diabetes
A disorder in which the body cells no longer respond properly to the insulin produced by the pancreas (insulin resistance).
What do scientists think causes Type 1 diabetes?
The person's own immune system destroys the insulin-making cells of the pancreas during development.
How is Type 1 diabetes normally treated?
With insulin injections.
How is Type 2 diabetes commonly treated?
With a carbohydrate-controlled diet and an exercise regime.
Why is obesity a major risk factor for Type 2 diabetes?
A diet rich in carbohydrates causes an over-production of insulin, which can result in insulin resistance.
How is BMI calculated, and what value indicates obesity?
BMI = mass (kg) ÷ height (m)². A BMI greater than 30 indicates obesity and an increased risk of Type 2 diabetes.
What does the waist-to-hip ratio indicate?
How much excess fat is stored around the abdomen; a high ratio is associated with an increased risk of Type 2 diabetes.
How is the waist-to-hip ratio calculated?
Waist circumference (cm) ÷ hip circumference (cm).
In diabetes the pancreas fails to produce enough insulin, whereas in Type 2 diabetes the body cells become to insulin.
Type 1 / resistant
An individual is classified as obese if their is greater than .
BMI / 30
Sign up to unlock flashcards
or