Biology · Both
Homeostasis & Hormones
Keeping internal conditions constant, blood glucose control, insulin and glucagon, and negative feedback.
Homeostasis is the maintenance of a constant internal environment. Hormones are chemical messengers carried in the blood that help coordinate responses.
What is homeostasis?
Examples of conditions kept steady:
• Body temperature (around 37°C)
• Blood glucose concentration
• Water balance
If conditions change too much, enzymes may not work properly and cells can be damaged.
Blood glucose control
The pancreas monitors blood glucose.
**If blood glucose is too high** (e.g. after a meal):
• Pancreas releases **insulin**
• Insulin causes liver and muscle cells to take up glucose and store it as **glycogen**
• Blood glucose falls
**If blood glucose is too low**:
• Pancreas releases **glucagon**
• Glucagon causes liver to break down glycogen into glucose
• Blood glucose rises
This is an example of **negative feedback** – the response reverses the change.
Worked example
Which hormone lowers blood glucose?
Solution
**Insulin**.
Diabetes (brief)
• **Type 1** – pancreas does not produce enough insulin; treated with insulin injections
• **Type 2** – body cells less responsive to insulin; linked to lifestyle; managed with diet, exercise, sometimes medication
Practice questions
Try these without looking at the answers first.
Q1.What is homeostasis?
Show answer
Maintaining a constant internal environment
Q2.Which organ produces insulin?
Show answer
Pancreas
Q3.What does glucagon do?
Show answer
Raises blood glucose (breaks down glycogen in liver)