Hormones
Introduced| English | Meaning |
|---|---|
| hormones/ˈhɔːməʊnz/ | Chemical messengers released by cells or glands that act on target cells with suitable receptors. |
| gland/ɡlænd/ | An organ or group of cells that produces and releases a substance. |
| endocrine system/ˈendəʊkraɪn ˈsɪstəm/ | The glands and tissues that release hormones into the blood to coordinate body functions. |
| target organs/ˈtɑːɡɪt ˈɔːɡənz/ | The organs with receptors for a particular hormone, so they respond to it. |
| insulin/ˈɪnsjuːlɪn/ | A hormone produced by pancreatic beta cells that helps lower blood glucose concentration. |
| adrenaline/əˈdrenəlɪn/ | A hormone released by the adrenal medulla that prepares the body for rapid action during stress or excitement. |
Chemical messengers
- Not all the body's messages are electrical. Some are chemicals carried in the blood.
- These are hormones 激素, made by glands 腺体 of the endocrine system 内分泌系统.
A hormone is a chemical messenger carried in the:
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Hormones travel in the blood to target organs.
Hormones are produced by organs called ______.
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Endocrine glands secrete hormones into the blood.
What hormones are
- A hormone is a chemical messenger made by a gland and carried in the blood.
- It affects specific target organs 靶器官.
Insulin 胰岛素 lowers blood glucose and glucagon raises it, keeping it near a normal level
How hormones work
Hormones are chemical messengers carried in the blood — slower than nerves, but longer-lasting.
Adrenaline prepares the body for:
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Adrenaline is the fight-or-flight hormone.
Insulin, made by the pancreas, acts to:
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Insulin lowers blood glucose.
Some key hormones
- Adrenaline 肾上腺素 (adrenal glands): prepares the body for action ("fight or flight").
- Insulin (pancreas): lowers blood glucose.
- Testosterone / oestrogen: control development and reproduction.
Hormonal responses are usually slower but longer-lasting than nervous responses.
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Nerves are fast and brief; hormones are slower and widespread.
Nerves vs hormones
- Nervous signals are fast and short-lived, sent to a precise place.
- Hormonal signals are slower but longer-lasting, spread through the blood.
Worked example. Facing danger, your adrenal glands release adrenaline into the blood. It reaches the heart (faster beat), muscles and liver — preparing your whole body to fight or flee within seconds.
You've got it
- a hormone is a chemical messenger made by a gland, carried in the blood
- examples: adrenaline (fight or flight), insulin (lowers glucose), sex hormones
- nerves = fast, brief, precise; hormones = slower, longer-lasting, widespread