📚 IGCSE CIE Biology: Endocrine System Key Points | 内分泌系统 考点精讲
The endocrine system is a network of glands that secrete hormones directly into the blood, regulating processes such as growth, metabolism, and reproduction. In IGCSE CIE Biology, you need to know the major glands, their hormones, and how negative feedback maintains homeostasis.
内分泌系统是由腺体组成的网络，直接将激素分泌到血液中，调节生长、代谢和生殖等过程。在IGCSE CIE生物中，你需要掌握主要腺体、其激素以及负反馈如何维持稳态。
1. Endocrine System Overview | 内分泌系统概述
Hormones are chemical messengers produced by endocrine glands. They travel in the bloodstream to target organs, where they trigger specific responses. Compared to the nervous system, the endocrine system tends to produce slower, longer-lasting effects.
激素是由内分泌腺产生的化学信使。它们随血流到达靶器官，在那里触发特定反应。与神经系统相比，内分泌系统通常产生较慢但更持久的效果。
Key glands include the pituitary, thyroid, adrenal, pancreas, ovaries and testes. Each gland releases one or more hormones that help maintain a stable internal environment through feedback mechanisms.
主要腺体包括垂体、甲状腺、肾上腺、胰腺、卵巢和睾丸。每个腺体释放一种或多种激素，通过反馈机制帮助维持稳定的内环境。
2. Hormones vs Nerve Impulses | 激素与神经冲动的比较
Hormones are chemical signals transported by the blood, so they act slowly but have long-lasting effects and can affect multiple organs. Nerve impulses are electrical signals that travel along neurones; they produce rapid, short-lived and highly localised responses.
激素是由血液运输的化学信号，因此作用缓慢但效果持久，并可以影响多个器官。神经冲动是沿神经元传导的电信号，产生快速、短暂且高度局域的反应。
A hormone’s effect may take seconds to hours to appear and can persist for minutes to days. In contrast, a nerve impulse can trigger a muscle contraction in milliseconds but stops quickly when stimulation ends.
激素的效应可能需要几秒到几小时才能出现，并可持续数分钟到数天。而神经冲动可在毫秒内触发肌肉收缩，但刺激停止时迅速终止。
- Hormones: chemical, blood, slow, long-lasting, widespread
- Nerve impulses: electrical, neurones, rapid, short-lived, localised
- 激素：化学信号、血液运输、缓慢、持久、作用广泛
- 神经冲动：电信号、神经元传导、快速、短暂、作用局限
3. Endocrine Glands and Their Hormones | 内分泌腺及其激素
The table below summarises the major glands, their hormones and main functions, as required by the CIE IGCSE specification. Remember that some glands are also exocrine (e.g. the pancreas secretes digestive enzymes as well as hormones).
下表总结了CIE IGCSE要求的主要腺体、其激素和主要功能。请记住有些腺体同时具有外分泌功能（例如胰腺既分泌消化酶又分泌激素）。
| Gland (腺体) | Hormone(s) (激素) | Target (靶器官/组织) | Main Function (主要功能) |
|---|---|---|---|
| Pituitary (垂体) | TSH, FSH, LH, ADH (vasopressin), growth hormone | Thyroid, ovaries/testes, kidneys, many tissues | Controls other glands, water balance, growth |
| Thyroid (甲状腺) | Thyroxine (甲状腺素) | Most body cells | Regulates basal metabolic rate |
| Adrenal (肾上腺) | Adrenaline (肾上腺素) | Heart, liver, muscles, iris | ‘Fight or flight’ response |
| Pancreas (胰腺) | Insulin (胰岛素), glucagon (胰高血糖素) | Liver, muscles | Regulates blood glucose concentration |
| Ovaries (卵巢) | Oestrogen (雌激素) | Female reproductive organs, body cells | Secondary sexual characteristics, menstrual cycle regulation |
| Testes (睾丸) | Testosterone (睾酮) | Male reproductive organs, muscles | Secondary sexual characteristics, sperm production |
In the following sections, we explore each gland in more detail, linking structure, hormone action and negative feedback where relevant.
在以下章节中，我们将更详细地探讨每个腺体，并关联结构、激素作用和负反馈机制。
4. The Pituitary Gland | 垂体
The pituitary gland is a pea-sized structure at the base of the brain, often called the ‘master gland’ because it controls the activity of several other endocrine glands. It is connected to the hypothalamus, which regulates its secretions.
垂体是位于脑底的豌豆大小的结构，常被称为“主腺”，因为它控制其他几个内分泌腺的活动。它与下丘脑相连，下丘脑调节其分泌物。
It produces TSH (thyroid-stimulating hormone), which stimulates the thyroid to release thyroxine. FSH and LH control the ovaries and testes, triggering gamete production and sex hormone release. ADH (vasopressin) acts on the kidneys to increase water reabsorption. Growth hormone promotes cell division and protein synthesis, affecting growth of bones and muscles.
它分泌促甲状腺激素(TSH)，刺激甲状腺释放甲状腺素。促卵泡激素(FSH)和促黄体生成素(LH)控制卵巢和睾丸，引发配子产生和性激素释放。抗利尿激素(ADH)作用于肾脏，增加水重吸收。生长激素促进细胞分裂和蛋白质合成，影响骨骼和肌肉的生长。
Because it releases tropic hormones that control other glands, the pituitary is central to the endocrine system. A deficiency or excess of its hormones can have wide-ranging effects on growth, metabolism and reproduction.
因为它分泌控制其他腺体的促激素，垂体在内分泌系统中处于核心地位。其激素缺乏或过量会对生长、代谢和生殖产生广泛影响。
5. Thyroid Gland and Thyroxine | 甲状腺和甲状腺素
The thyroid gland is located in the neck. It produces thyroxine, a hormone containing iodine. Thyroxine controls the basal metabolic rate (BMR) – the speed at which chemical reactions occur in the body at rest.
甲状腺位于颈部。它产生甲状腺素，一种含碘的激素。甲状腺素控制基础代谢率(BMR)，即身体在休息时化学反应发生的速度。
Too little thyroxine leads to weight gain, tiredness and feeling cold. Too much causes weight loss, increased heart rate and sweating. Iodine deficiency prevents normal thyroxine production and can cause the thyroid to swell, forming a goitre.
甲状腺素过少会导致体重增加、疲倦和怕冷。过多则引起体重减轻、心率加快和出汗。碘缺乏会阻碍甲状腺素的正常产生，并可能使甲状腺肿大，形成甲状腺肿。
Thyroxine secretion is controlled by a negative feedback loop involving the pituitary. When thyroxine levels fall, the pituitary releases more TSH; when they rise, TSH release is inhibited. This keeps the BMR within a narrow range.
甲状腺素的分泌受垂体参与的负反馈环控制。当甲状腺素水平下降时，垂体释放更多TSH；当水平升高时，TSH释放被抑制，从而使BMR保持在狭窄的范围内。
6. Adrenal Gland and Adrenaline | 肾上腺和肾上腺素
The adrenal glands are located on top of each kidney. The inner region (medulla) secretes adrenaline in response to stress, fear or excitement. Adrenaline prepares the body for ‘fight or flight’.
肾上腺位于每个肾脏的上方。其内部区域（髓质）在应激、恐惧或兴奋时分泌肾上腺素。肾上腺素使身体为“战或逃”做好准备。
It increases heart rate and breathing rate, delivering more oxygen to muscles. It dilates the pupils to improve vision. It stimulates the liver to convert glycogen into glucose, raising blood glucose concentration so that muscles have more fuel. Blood is diverted away from the skin and digestive system towards the muscles.
它提高心率和呼吸频率，向肌肉输送更多氧气。它使瞳孔扩张以改善视力。它刺激肝脏将糖原转化为葡萄糖，升高血糖浓度，使肌肉获得更多能量。血液从皮肤和消化系统转向肌肉。
These changes happen within seconds and are short-lived, as adrenaline is quickly broken down. The response illustrates how the endocrine system can work rapidly when needed, complementing the nervous system.
这些变化在几秒内发生且短暂，因为肾上腺素会迅速分解。这一反应说明内分泌系统在需要时可以快速工作，与神经系统互补。
7. Pancreas and Blood Glucose Regulation | 胰腺和血糖调节
The pancreas contains clusters of endocrine cells called islets of Langerhans. Alpha cells in the islets produce glucagon, and beta cells produce insulin. Both hormones regulate blood glucose concentration.
胰腺中含有称为胰岛的内分泌细胞团。胰岛内的α细胞产生胰高血糖素，β细胞产生胰岛素。这两种激素调节血糖浓度。
After a meal, blood glucose rises. The beta cells detect the increase and secrete insulin. Insulin binds to receptors on liver and muscle cells, causing them to take up glucose and convert it into glycogen for storage. This lowers blood glucose back to normal.
进食后，血糖升高。β细胞检测到上升并分泌胰岛素。胰岛素与肝细胞和肌细胞上的受体结合，促使它们摄取葡萄糖并将其转化为糖原储存，从而将血糖降回正常水平。
When blood glucose falls, alpha cells secrete glucagon. Glucagon stimulates the liver to break down glycogen into glucose and release it into the blood, raising blood glucose. These antagonistic hormones maintain blood glucose within a narrow range around 90 mg per 100 cm³ of blood.
当血糖下降时，α细胞分泌胰高血糖素。胰高血糖素刺激肝脏将糖原分解为葡萄糖并释放入血，升高血糖。这些拮抗激素将血糖维持在约90毫克/100立方厘米血液的狭窄范围内。
8. Insulin and Glucagon: Negative Feedback | 胰岛素与胰高血糖素：负反馈
The control of blood glucose is a classic example of negative feedback. A rise in blood glucose triggers insulin release, which lowers glucose. A fall triggers glucagon release, which raises glucose. Once the normal level is restored, the hormone secretion is reduced.
血糖的控制是负反馈的经典例子。血糖升高触发胰岛素释放，胰岛素降低血糖。血糖下降触发胰高血糖素释放，胰高血糖素升高血糖。一旦恢复正常水平，激素分泌就会减少。
This continuous monitoring and correction prevents extreme hyperglycaemia or hypoglycaemia. The liver plays a central role as the main store of glycogen. Muscles also store glycogen for their own use, responding to insulin.
这种持续的监测与纠正防止了极度高血糖或低血糖。肝脏作为糖原的主要储存库起着核心作用。肌肉也会储存糖原供自身使用，并对胰岛素产生反应。
High blood glucose → insulin released → glucose taken into cells and stored as glycogen → blood glucose falls.
Low blood glucose → glucagon released → glycogen converted to glucose → blood glucose rises.
高血糖 → 胰岛素释放 → 葡萄糖进入细胞并储存为糖原 → 血糖下降。
低血糖 → 胰高血糖素释放 → 糖原转化为葡萄糖 → 血糖上升。
9. Diabetes Mellitus | 糖尿病
Diabetes mellitus is a condition where blood glucose concentration remains too high. There are two main types: Type 1 and Type 2.
糖尿病是一种血糖浓度持续过高的疾病。主要有两种类型：1型和2型。
In Type 1 diabetes, the body’s immune system destroys the beta cells in the pancreas, so little or no insulin is produced. It often develops in childhood. Patients require regular insulin injections to control blood glucose and must monitor their diet carefully.
在1型糖尿病中，身体的免疫系统破坏胰腺中的β细胞，因此产生的胰岛素很少或没有。它通常在儿童期出现。患者需要定期注射胰岛素来控制血糖，并必须仔细监测饮食。
In Type 2 diabetes, the target cells (especially in the liver and muscles) become resistant to insulin, meaning they do not respond properly. This type is often linked to obesity, a sedentary lifestyle and a diet high in sugar. Treatment involves a controlled diet, increased physical activity and sometimes medication to improve insulin sensitivity.
在2型糖尿病中，靶细胞（特别是肝细胞和肌细胞）对胰岛素产生抗性，即它们不能正常响应。这种类型常与肥胖、久坐不动的生活方式和高糖饮食有关。治疗包括控制饮食、增加体育活动，有时需要药物来提高胰岛素敏感性。
Both types can lead to complications if poorly managed, including damage to blood vessels, nerves and kidneys. Maintaining blood glucose within the normal range is essential.
如果管理不善，两种类型都可能导致并发症，包括血管、神经和肾脏的损伤。将血糖维持在正常范围内至关重要。
10. Ovaries and Oestrogen / Testes and Testosterone | 卵巢与雌激素 / 睾丸与睾酮
The ovaries produce oestrogen, the main female sex hormone. Oestrogen promotes the development of secondary sexual characteristics at puberty, such as breast development, widening of the hips and the onset of the menstrual cycle. It also helps regulate ovulation and prepares the uterus for possible pregnancy.
卵巢产生雌激素，即主要的女性性激素。雌激素在青春期促进第二性征的发育，如乳房发育、臀部变宽和月经周期的开始。它还有助于调节排卵并为可能的怀孕准备子宫。
The testes produce testosterone, the main male sex hormone. Testosterone stimulates the development of secondary sexual characteristics such as a deepening of the voice, growth of facial and body hair, and increased muscle mass. It is also essential for sperm production (spermatogenesis).
睾丸产生睾酮，即主要的男性性激素。睾酮刺激第二性征的发育，如声音变低沉、面部和体毛生长以及肌肉量增加。它对于精子生成（精子发生）也至关重要。
In both sexes, the release of these hormones is controlled by pituitary hormones FSH and LH, forming a feedback loop that maintains appropriate levels.
在两性中，这些激素的释放由垂体激素FSH和LH控制，形成一个反馈环，维持适当水平。
11. ADH and Water Balance | 抗利尿激素与水盐平衡
ADH (antidiuretic hormone), also known as vasopressin, is produced by the hypothalamus and released from the posterior pituitary. It controls water reabsorption in the kidneys, helping to keep the water potential of the blood constant.
抗利尿激素(ADH)，也称为加压素，由下丘脑产生并从垂体后叶释放。它控制肾脏中的水重吸收，帮助维持血液水势的恒定。
When blood water potential falls (e.g. after sweating or low water intake), osmoreceptors in the
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