📚 Endocrine System: Exam-Focused Revision for IGCSE Biology | 内分泌系统考点精讲
The endocrine system is a collection of glands that secrete hormones directly into the bloodstream. Unlike the nervous system, which uses electrical impulses for rapid, short-lived responses, the endocrine system relies on chemical messengers that travel through the blood to target organs. This system helps regulate metabolism, growth, reproduction, stress responses and water balance. For the Edexcel IGCSE Biology exam, you are expected to know the main endocrine glands, the hormones they produce, and how negative feedback loops maintain homeostasis. Let’s dive into the key facts and concepts that will secure you top marks.
内分泌系统是由一些腺体组成的集合，这些腺体将激素直接分泌到血液中。与用电信号产生快速而短暂反应的神经系统不同，内分泌系统依靠化学信使经血液到达靶器官。这套系统有助于调节新陈代谢、生长、生殖、应激反应和水分平衡。在 Edexcel IGCSE 生物考试中，你需要了解主要的内分泌腺、它们产生的激素，以及负反馈环路如何维持体内稳态。下面我们深入掌握能帮你拿高分的关键事实和概念。
1. Endocrine Glands and Hormones | 内分泌腺与激素
An endocrine gland is a structure that produces and releases hormones directly into the blood. Unlike exocrine glands, endocrine glands have no ducts. Hormones are chemical substances that travel through the bloodstream and affect specific target cells or organs that possess complementary receptor proteins.
内分泌腺是制造激素并将其直接释放入血液的结构。与外分泌腺不同，内分泌腺没有导管。激素是一种化学物质，通过血液循环运输，并作用于具有互补受体蛋白的特定靶细胞或靶器官。
The key glands you must know for the exam include:
考试必须了解的关键腺体包括：
- Pituitary gland – produces ADH (antidiuretic hormone) and TSH (thyroid-stimulating hormone)
- Thyroid gland – produces thyroxine
- Adrenal glands – produce adrenaline
- Pancreas (Islets of Langerhans) – produces insulin and glucagon
- Ovaries – produce oestrogen and progesterone
- Testes – produce testosterone
- 垂体 – 产生抗利尿激素 (ADH) 和促甲状腺激素 (TSH)
- 甲状腺 – 产生甲状腺素
- 肾上腺 – 产生肾上腺素
- 胰腺（胰岛） – 产生胰岛素和胰高血糖素
- 卵巢 – 产生雌激素和孕酮
- 睾丸 – 产生睾酮
Understanding the source of each hormone is essential; exam questions often ask you to match a hormone to its gland.
弄清楚每种激素的来源至关重要；考试题经常要求你将激素与其腺体对应起来。
2. How Hormones Work | 激素的作用方式
Hormones are transported in the blood plasma, so their effects may take seconds to hours to appear, but they tend to last longer than nerve impulses. Each hormone binds to specific receptors on or inside its target cells, triggering a response that alters the cell’s activity. Because hormones circulate throughout the body, a single hormone can coordinate changes in multiple organs at once, but only those cells with the correct receptors will respond.
激素通过血浆运输，因此它们的作用可能需要几秒到几小时才会显现，但效果通常比神经冲动持续更久。每种激素与其靶细胞表面或内部的特定受体结合，触发改变细胞活性的反应。由于激素在全身循环，单一激素可以同时协调多个器官的变化，但只有那些具有正确受体的细胞才会作出回应。
For example, insulin attaches to receptors on liver and muscle cells, causing them to take up glucose. Adrenaline binds to receptors in the heart, liver and blood vessels, producing a ‘fight-or-flight’ response.
例如，胰岛素与肝细胞和肌细胞的受体结合，使它们摄取葡萄糖。肾上腺素与心脏、肝脏和血管上的受体结合，产生“战斗或逃跑”反应。
3. Endocrine vs Nervous Systems | 内分泌系统与神经系统的比较
Exam questions frequently ask you to compare the two communication systems. Use these points:
考试题经常要求你对这两个通讯系统进行比较。请记住以下要点：
Nervous system: uses electrical impulses along neurones; very fast (milliseconds); short-lived effects; acts on a specific localised area (muscles or glands).
神经系统：沿神经元传递电信号；速度极快（毫秒级）；效果短暂；作用于特定的局部区域（肌肉或腺体）。
Endocrine system: uses chemical hormones in the blood; slower (seconds to days); long-lasting effects; may act on multiple target organs throughout the body.
内分泌系统：在血液中利用化学激素传递信息；速度较慢（数秒至数日）；效果持久；可作用于全身多个靶器官。
Make sure to mention that the nervous system is ideal for immediate responses, while the endocrine system controls long-term processes like growth and reproduction.
务必要提到神经系统适合即时反应，而内分泌系统控制生长、生殖等长期过程。
4. Blood Glucose Regulation: Insulin and Glucagon | 血糖调节：胰岛素与胰高血糖素
The pancreas monitors and controls blood glucose concentration. After a carbohydrate-rich meal, blood glucose rises. The pancreas detects this and the beta cells in the Islets of Langerhans secrete insulin. Insulin travels to the liver and muscles, stimulating them to convert excess glucose into glycogen for storage. This reduces blood glucose back to normal levels.
胰腺监测并控制血糖浓度。进食富含碳水化合物的食物后，血糖升高。胰腺检测到这一变化，胰岛中的 β 细胞分泌胰岛素。胰岛素到达肝脏和肌肉，刺激它们将多余的葡萄糖转化为糖原储存起来。这样便使血糖回落至正常水平。
Glucose → Glycogen (glycogenesis)
葡萄糖 → 糖原（糖生成）
When blood glucose drops, alpha cells in the pancreas release glucagon. Glucagon prompts the liver to break glycogen back into glucose and release it into the blood, raising the concentration. This is negative feedback — the system opposes the change.
当血糖下降时，胰腺的 α 细胞释放胰高血糖素。胰高血糖素促使肝脏将糖原分解回葡萄糖并释放入血，从而提高血糖浓度。这就是负反馈——系统对抗变化的方向。
Glycogen → Glucose (glycogenolysis)
糖原 → 葡萄糖（糖原分解）
5. Diabetes: Type 1 | 糖尿病：1 型
Type 1 diabetes is an autoimmune condition in which the body’s immune system attacks the beta cells of the pancreas, so little or no insulin is produced. Consequently, blood glucose remains high after a meal, which can damage organs. People with type 1 diabetes monitor their blood sugar and inject insulin at mealtimes to enable glucose uptake by cells. Exam questions may also ask why insulin must be injected rather than swallowed: the hormone is a protein that would be digested in the stomach if taken orally.
1 型糖尿病是一种自身免疫性疾病，免疫系统攻击胰腺的 β 细胞，因此体内几乎不产生胰岛素。这样一来，餐后血糖持续保持高位，可能损害器官。1 型糖尿病患者需监测血糖，并在进餐时注射胰岛素，使细胞能够摄取葡萄糖。考试还可能会问为什么胰岛素必须注射而不能口服：因为胰岛素是一种蛋白质，若口服会在胃里被消化。
Remember the distinction: type 1 is insulin-dependent, whereas type 2 (not required in this syllabus) involves insulin resistance.
牢记区别：1 型依赖胰岛素，而 2 型（本考纲不要求）涉及胰岛素抵抗。
6. Adrenaline and the Fight-or-Flight Response | 肾上腺素与“战斗或逃跑”反应
Adrenaline is released by the adrenal glands on top of the kidneys in times of fear or stress. Its role is to prepare the body for intense physical activity. Once in the bloodstream, adrenaline brings about several changes:
肾上腺素由位于肾脏上方的肾上腺在恐惧或压力下释放。其作用是为身体做好剧烈运动的准备。一旦进入血液，肾上腺素会引发数种变化：
- Increases heart rate and stroke volume – more oxygen and glucose are delivered to muscles
- Dilates bronchioles – more air enters the lungs
- Stimulates liver glycogenolysis – raises blood glucose for respiration
- Dilates pupils – improves vision
- 提高心率和每搏输出量 – 将更多氧气和葡萄糖输送到肌肉
- 扩张细支气管 – 更多空气进入肺部
- 刺激肝脏糖原分解 – 提高血糖以供呼吸
- 放大瞳孔 – 改善视力
These effects are all designed to boost performance in a ‘fight-or-flight’ emergency. Adrenaline is inactivated quickly once the threat passes.
这些效应都旨在提升“战斗或逃跑”紧急状况下的表现。一旦威胁解除，肾上腺素会迅速失活。
7. Water Balance and Anti-Diuretic Hormone (ADH) | 水分平衡与抗利尿激素
Water balance is controlled by ADH, a hormone made in the hypothalamus and released from the pituitary gland. When blood becomes too concentrated (high solute concentration), osmoreceptors in the hypothalamus detect this and stimulate the release of ADH. ADH acts on the collecting ducts of the kidney nephrons, making them more permeable to water so more water is reabsorbed back into the blood. This produces a small volume of concentrated urine.
水分平衡由抗利尿激素 (ADH) 调控，它在下丘脑制造、从垂体释放。当血液变得过浓（溶质浓度高）时，下丘脑的渗透压感受器检测到这一变化，刺激 ADH 释放。ADH 作用于肾单位的集合管，使其对水的通透性增大，于是更多水分被重吸收回血液。这便产生少量浓缩尿。
If blood is too dilute, less ADH is released, the collecting ducts become less permeable, and more water is excreted in dilute urine. This negative feedback loop maintains the blood’s water potential within narrow limits.
如果血液过稀，ADH 释放减少，集合管通透性降低，更多水分随稀释尿液排出。这一负反馈环路将血液的水势维持在一个窄幅范围内。
8. Thyroxine and Negative Feedback | 甲状腺素与负反馈
Thyroxine is a hormone produced by the thyroid gland in the neck. It controls the body’s basal metabolic rate (BMR), i.e. how quickly chemical reactions occur in cells. The regulation of thyroxine is a classic Edexcel negative feedback example:
甲状腺素是由颈部甲状腺产生的激素。它控制人体的基础代谢率 (BMR)，即细胞内化学反应进行的快慢。甲状腺素的调节是 Edexcel 课程中典型的负反馈实例：
When blood thyroxine level falls, the pituitary gland releases more thyroid-stimulating hormone (TSH). TSH travels to the thyroid and stimulates it to secrete more thyroxine. As thyroxine rises back to normal, it inhibits further TSH release — this self-limiting mechanism keeps the system stable.
当血中甲状腺素水平下降时，垂体释放更多促甲状腺激素 (TSH)。TSH 抵达甲状腺并刺激其分泌更多甲状腺素。当甲状腺素回升至正常水平时，它会抑制 TSH 的进一步释放——这种自我限制机制使系统保持稳定。
↓ Thyroxine → ↑ TSH → ↑ Thyroxine → ↓ TSH
↓ 甲状腺素 → ↑ TSH → ↑ 甲状腺素 → ↓ TSH
An overactive thyroid (hyperthyroidism) can lead to weight loss and increased heart rate; an underactive thyroid (hypothyroidism) causes tiredness and weight gain.
甲状腺功能亢进会导致体重下降和心率加快；甲状腺功能减退则引起疲倦和体重增加。
9. Reproductive Hormones | 生殖激素
The testes produce testosterone, which stimulates the development of male secondary sexual characteristics such as facial hair, deepening of the voice and muscle growth. Testosterone also promotes sperm production.
睾丸产生睾酮，能促进男性第二性征的发育，例如胡须、声音变深沉和肌肉生长。睾酮还促进精子生成。
The ovaries produce oestrogen and progesterone. Oestrogen is responsible for female secondary sexual characteristics, including breast development and widening of the hips, and it helps regulate the menstrual cycle. Progesterone maintains the uterine lining during pregnancy and prepares the uterus for implantation.
卵巢产生雌激素和孕酮。雌激素负责女性第二性征，包括乳房发育和臀部变宽，并帮助调节月经周期。孕酮在怀孕期间维持子宫内膜，为受精卵着床做好准备。
For IGCSE, you are not required to memorise the details of the menstrual cycle, but you must know the sources and main roles of these three reproductive hormones.
在 IGCSE 阶段，你不必记忆月经周期的细节，但必须知道这三种生殖激素的来源和主要作用。
10. Exam Technique and Common Pitfalls | 答题技巧与常见失分点
Use precise terminology. Always name the specific gland and hormone. Instead of writing ‘the gland that releases insulin’, say ‘the pancreas (Islets of Langerhans)’. Avoid vague terms like ‘sugar’ — use ‘glucose’ or ‘glycogen’.
使用精确术语。始终写出具体的腺体和激素名称。不要写“释放胰岛素的腺体”，而要写“胰腺（胰岛）”。避免使用“糖”这样的模糊词汇——要写“葡萄糖”或“糖原”。
Explain negative feedback clearly. A common error is to state that a rise in thyroxine causes TSH to increase. Make it clear: when thyroxine is high, TSH release is inhibited. Use arrows or simple diagrams in your answer to show the loop.
清晰解释负反馈。一个常见错误是认为甲状腺素升高会导致 TSH 增加。务必阐明：当甲状腺素水平高时，TSH 释放受到抑制。答案中可以用箭头或简单示意图展示这一环路。
Link hormone to mode of delivery. Adrenaline and insulin are proteins — they cannot be taken as tablets because they would be digested. This is a frequent application question.
将激素与给药途径联系起来。肾上腺素和胰岛素属于蛋白质——它们不能做成药片服用，因为会被消化。这是一道常见的应用题。
Don’t confuse nervous and endocrine. If a question asks for a long-term, body-wide response, choose hormones; if it asks for an immediate, localised response, choose neurones.
不要混淆神经与内分泌。若题目问长期、全身性反应，选择激素；若问即时、局部反应，选择神经元。
Finally, practice matching glands to hormones and linking hormones to their target tissues — these straight recall questions often appear in multiple-choice and short-answer sections.
最后，多做腺体与激素配对，以及激素与其靶组织关联的练习——这类直接回忆题常出现在选择题和简答题中。
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