Hormones
Year 9 ๐ซ Physiology & Health Endocrine glands, hormones, and feedback mechanisms.
๐ The Endocrine System
Hormones are chemical messengers transported in the blood from endocrine glands to target organs.
| Gland | Hormone(s) | Target / Effect |
|---|---|---|
| Pancreas | Insulin, Glucagon | Liver and cells: regulate blood glucose |
| Adrenal glands | Adrenaline | Heart, muscles, liver: fight-or-flight response |
| Thyroid | Thyroxine | All cells: regulates metabolic rate |
| Pituitary | FSH, LH, ADH, growth hormone | Various: "master gland" |
| Ovaries | Oestrogen, Progesterone | Uterus, sex characteristics |
| Testes | Testosterone | Sperm production, sex characteristics |
๐ Nervous vs Hormonal Control
| Feature | Nervous system | Hormonal system |
|---|---|---|
| Signal type | Electrical impulse | Chemical (hormone in blood) |
| Speed | Very fast (milliseconds) | Slower (seconds to minutes) |
| Duration | Short-lived | Longer lasting |
| Range | Specific pathway | Widespread (bloodstream) |
| Examples | Reflexes, muscle contraction | Growth, blood glucose regulation, menstrual cycle |
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