The endocrine system
Glands and hormones
The endocrine system is a network of glands that release hormones — chemical messengers carried in the blood — to target organs with the right receptors.
| Gland | Hormone(s) | Effect |
|---|---|---|
| Pituitary ("master gland") | FSH, LH, ADH, growth | Controls other glands |
| Thyroid | Thyroxine | Sets metabolic rate |
| Adrenal | Adrenaline | Fight-or-flight |
| Pancreas | Insulin, glucagon | Blood glucose |
| Ovaries | Oestrogen | Menstrual cycle |
| Testes | Testosterone | Male development |
Compared with the nervous system, hormonal effects are slower, longer-lasting and act over a wider area.
Blood glucose regulation
The pancreas monitors glucose and releases hormones into the blood:
- Glucose too high → pancreas releases insulin → liver/muscle cells take up glucose and store it as glycogen → glucose falls.
- Glucose too low → pancreas releases glucagon → liver converts glycogen → glucose released → glucose rises.
This is negative feedback — the response reverses the change.
Type 1 diabetes
The body's immune system destroys insulin-producing cells in the pancreas. Usually appears in childhood.
- Cannot make insulin → blood glucose rises rapidly after meals.
- Treated with insulin injections matched to food intake; blood glucose monitored throughout the day.
Type 2 diabetes
Body cells stop responding to insulin (insulin resistance). Strongly linked to obesity and a sedentary lifestyle; usually appears in adulthood.
- Treated with diet and exercise first; medication later if needed.
OCR exam tip
If the question says "compare", make every point a true comparison ("X does this, Y does that") — single statements about only one disease cap your marks.
AI-generated · claude-opus-4-7 · v3-ocr-combined-science-leaves