# Hormones and the Endocrine System
The endocrine system uses hormones (chemical messengers) carried in the blood to coordinate slower, longer-lasting responses compared to the nervous system.
1. Endocrine Glands
| Gland | Hormone | Function |
|---|---|---|
| Pituitary | Various (FSH, LH, ADH, growth hormone) | "Master gland" — controls other glands |
| Thyroid | Thyroxine | Controls metabolic rate |
| Adrenal | Adrenaline | Fight-or-flight response |
| Pancreas | Insulin and glucagon | Blood glucose regulation |
| Ovaries | Oestrogen, progesterone | Female reproductive hormones |
| Testes | Testosterone | Male reproductive hormone |
2. Nervous vs Endocrine System
| Feature | Nervous | Endocrine |
|---|---|---|
| Signal type | Electrical impulses | Chemical (hormones in blood) |
| Speed | Fast | Slower |
| Duration | Short-lived | Long-lasting |
| Target | Specific (along neurones) | Widespread (via blood) |
3. Blood Glucose Regulation
After Eating (glucose too high)
- Pancreas detects high blood glucose
- Insulin released
- Insulin causes liver and muscle cells to absorb glucose → stored as glycogen
- Blood glucose falls
During Exercise/Fasting (glucose too low)
- Pancreas detects low blood glucose
- Glucagon released
- Glucagon causes liver to convert glycogen → glucose
- Blood glucose rises
This is negative feedback — the response opposes the change.
4. Diabetes
| Type 1 | Type 2 | |
|---|---|---|
| Cause | Autoimmune — pancreas can't make insulin | Body cells become resistant to insulin |
| Onset | Usually childhood | Usually later in life |
| Treatment | Insulin injections | Diet, exercise, medication |
| Risk factors | Genetic | Obesity, inactivity, diet, genetics |
5. Reproductive Hormones and the Menstrual Cycle
| Hormone | Gland | Function |
|---|---|---|
| FSH | Pituitary | Stimulates egg maturation; stimulates oestrogen production |
| Oestrogen | Ovaries | Thickens uterus lining; inhibits FSH; stimulates LH |
| LH | Pituitary | Triggers ovulation (day 14) |
| Progesterone | Ovaries (corpus luteum) | Maintains uterus lining; inhibits FSH and LH |
Contraception
- Hormonal: pill (oestrogen + progesterone), implant, injection, IUS
- Barrier: condom, diaphragm
- IVF uses FSH and LH to stimulate multiple egg production
6. Practice Questions
- Explain how insulin lowers blood glucose levels.
- Compare Type 1 and Type 2 diabetes.
- Describe the role of FSH and LH in the menstrual cycle.
- What is negative feedback? Give an example.
- Compare the nervous and endocrine systems.
Want to check your answers and get step-by-step solutions?
Summary
- Endocrine: hormones in blood; slower but longer-lasting than nervous system
- Blood glucose: insulin (high → low); glucagon (low → high); negative feedback
- Diabetes: Type 1 (no insulin) vs Type 2 (insulin resistance)
- Menstrual cycle: FSH, oestrogen, LH, progesterone