📚 GCSE WJEC Biology: The Endocrine System – Key Revision Points | 内分泌系统考点精讲
The endocrine system is a vital communication network that uses chemical messengers called hormones to coordinate and regulate body functions. In WJEC GCSE Biology, you need to understand the key glands, their hormones, how negative feedback maintains balance, and specific examples such as blood glucose control, the fight-or-flight response, thyroxine regulation, and the menstrual cycle. This article covers all the essential revision points to help you prepare for your exam.
内分泌系统是一个重要的通讯网络，它使用激素这种化学信使来协调和调节身体机能。在 WJEC GCSE 生物学中，你需要掌握关键的内分泌腺、它们分泌的激素、负反馈如何维持稳态，以及一些具体实例，如血糖调控、战斗或逃跑反应、甲状腺素调节和月经周期等。本文将涵盖所有必考点，帮助你高效备考。
1. The Endocrine System Overview | 内分泌系统概述
The endocrine system consists of several glands distributed throughout the body. These glands secrete hormones directly into the blood, unlike exocrine glands that use ducts. The main endocrine glands include the pituitary, thyroid, pancreas, adrenal glands, ovaries and testes. Each hormone acts as a chemical messenger that travels in the blood and only affects target organs with specific receptor proteins.
内分泌系统由分布在全身的多个腺体组成。这些腺体将激素直接分泌到血液中，这与使用导管的外分泌腺不同。主要的内分泌腺包括垂体、甲状腺、胰腺、肾上腺、卵巢和睾丸。每种激素都是一种化学信使，通过血液运输，并且只作用于带有特定受体蛋白的靶器官。
Hormones can be proteins (e.g. insulin) or steroids (e.g. oestrogen). Because hormones circulate in the bloodstream, their effects may be slower to appear than nerve impulses, but they usually last longer and can influence several tissues at once if the correct receptors are present.
激素可以是蛋白质（如胰岛素）或类固醇（如雌激素）。由于激素在血液中循环，其作用可能比神经冲动来得慢，但通常持续时间更长，并且如果存在相应的受体，它们可以同时影响多个组织。
2. Comparing Nervous and Endocrine Systems | 神经系统与内分泌系统的比较
The nervous system uses electrical impulses along neurones to produce rapid, short‑lived responses. In contrast, the endocrine system employs hormones that are released into the blood, producing slower but more prolonged effects. Nervous impulses travel along a specific pathway, while hormones can be distributed throughout the whole body and will only activate cells that display the matching receptor.
神经系统利用沿神经元传导的电脉冲产生快速、短暂的反应。相比之下，内分泌系统使用的是释放到血液中的激素，其作用较慢但更持久。神经冲动沿着特定的路径传导，而激素可以分布到全身各处，并且只会激活带有相应受体的细胞。
For example, the reflex withdrawal of a hand from a hot object is a nervous response taking a fraction of a second, whereas the regulation of blood glucose by insulin and glucagon can take minutes to hours. Both systems are crucial for maintaining homeostasis and often work together — for instance, in the stress response, the nervous system triggers the adrenal glands to release adrenaline.
例如，手碰到热物体时的缩手反射是一种神经反应，仅需几分之一秒；而胰岛素和胰高血糖素对血糖的调节可能需要数分钟到数小时。两个系统对于维持稳态都至关重要，并且常常协同工作——例如，在应激反应中，神经系统会触发肾上腺释放肾上腺素。
3. Negative Feedback Loops | 负反馈调节环路
Negative feedback is a fundamental control mechanism that keeps internal conditions within narrow limits. When a factor such as blood glucose or hormone level rises above the normal set point, the body activates processes to reduce it. Conversely, when the level drops below normal, opposing processes are switched on to raise it back.
负反馈是一种基本的控制机制，能使内环境维持在狭窄的范围内。当血糖或激素水平等因子超过正常的设定值时，身体会启动相应的过程使其降低。反之，当水平低于正常值时，相反的过程就会被开启以使其回升。
A classic example is the regulation of blood glucose: a rise after a meal stimulates the pancreas to release insulin, which promotes glucose uptake and glycogen formation, lowering blood glucose. A fall in blood glucose triggers glucagon release, which stimulates glycogen breakdown, raising blood glucose. Negative feedback is also central to thyroxine levels and body temperature control.
一个典型的例子是血糖的调节：餐后血糖升高会刺激胰腺释放胰岛素，胰岛素促进葡萄糖摄取和糖原合成，从而降低血糖。血糖下降则会触发胰高血糖素的释放，促进糖原分解，使血糖升高。负反馈对甲状腺素水平和体温调控同样至关重要。
4. Blood Glucose Regulation: Insulin and Glucagon | 血糖调节：胰岛素与胰高血糖素
The pancreas contains clusters of endocrine cells called the islets of Langerhans. The α‑cells secrete glucagon, and the β‑cells secrete insulin. These two hormones work antagonistically to keep blood glucose concentration at roughly 4–7 mmol dm⁻³.
胰腺中含有称为胰岛的内分泌细胞团。α细胞分泌胰高血糖素，β细胞分泌胰岛素。这两种激素相互拮抗，将血糖浓度维持在约 4–7 mmol dm⁻³。
When blood glucose is too high (e.g. after eating), β‑cells release insulin. Insulin stimulates the liver and muscle cells to convert excess glucose into glycogen for storage. It also increases the uptake of glucose by cells. The overall effect is a reduction in blood glucose. When blood glucose is too low (e.g. during intense exercise), α‑cells release glucagon. Glucagon stimulates the liver to break down glycogen back into glucose and release it into the blood, raising blood glucose.
当血糖过高时（如餐后），β细胞释放胰岛素。胰岛素会刺激肝细胞和肌肉细胞将多余的葡萄糖转化为糖原储存起来，同时增加细胞对葡萄糖的摄取。最终效果是降低血糖。当血糖过低时（如剧烈运动时），α细胞释放胰高血糖素。胰高血糖素会刺激肝脏将糖原分解为葡萄糖并释放入血，从而提高血糖水平。
Glucose is transported in the blood as a simple sugar, and its storage form is glycogen. The conversion is controlled by enzymes that are activated or inhibited by these hormones. The entire process is a negative feedback loop.
葡萄糖以单糖的形式在血液中运输，其储存形式为糖原。这种转换由酶控制，而这些酶又受这两种激素的激活或抑制。整个过程是一个负反馈环路。
5. Diabetes: Type 1 and Type 2 | 糖尿病：1型与2型
Diabetes is a condition where the blood glucose level remains abnormally high. In Type 1 diabetes, the body’s own immune system destroys the insulin‑producing β‑cells in the pancreas, so little or no insulin is secreted. Sufferers require regular insulin injections and must carefully manage their diet and exercise.
糖尿病是一种血糖水平持续异常升高的疾病。在1型糖尿病中，人体自身的免疫系统破坏了胰腺中产生胰岛素的β细胞，因此极少甚至没有胰岛素分泌。患者需要定期注射胰岛素，并且必须谨慎管理饮食与运动。
Type 2 diabetes typically develops when the body’s cells become resistant to insulin, meaning they no longer respond properly to its signal. The pancreas may still produce insulin, often in large quantities, but it is ineffective. Risk factors include obesity, a sedentary lifestyle and a diet high in refined sugars. Type 2 diabetes can often be controlled by improving diet, increasing physical activity and losing weight, although medication may also be needed.
2型糖尿病通常是由于身体细胞对胰岛素产生抵抗性，即细胞不再对胰岛素信号做出正常响应而发病。胰腺可能仍能产生胰岛素，甚至分泌量很大，但其效用低下。风险因素包括肥胖、久坐不动的生活方式以及精制糖含量高的饮食。2型糖尿病通常可以通过改善饮食、增加体育活动和减轻体重来控制，不过有时也需要药物治疗。
Both types can lead to severe complications such as cardiovascular disease, nerve damage and kidney failure if blood glucose is not controlled properly.
如果血糖得不到适当控制，两种类型的糖尿病都可能导致严重的并发症，如心血管疾病、神经损伤和肾衰竭。
6. The Thyroid Gland and Thyroxine | 甲状腺与甲状腺素
The thyroid gland, located in the neck, produces the hormone thyroxine (T₄) which contains iodine. Thyroxine controls the basal metabolic rate – the rate at which cells carry out chemical reactions at rest. It is essential for normal growth and development.
甲状腺位于颈部，分泌含碘的甲状腺素（T₄）。甲状腺素控制基础代谢率，即细胞在静息状态下进行化学反应的速率，对正常的生长发育至关重要。
Thyroxine release is regulated by a negative feedback circuit involving the hypothalamus and the pituitary gland. The hypothalamus secretes TRH (thyrotropin‑releasing hormone), which stimulates the pituitary to release TSH (thyroid‑stimulating hormone). TSH then stimulates the thyroid to produce thyroxine. When blood thyroxine rises to a high level, it inhibits the secretion of both TRH and TSH, reducing production. If thyroxine levels fall, the inhibition is lifted and secretion increases again.
甲状腺素的释放受到下丘脑和垂体参与的负反馈回路调节。下丘脑分泌促甲状腺激素释放激素（TRH），刺激垂体释放促甲状腺激素（TSH）。TSH 再刺激甲状腺生成甲状腺素。当血液中甲状腺素水平升高至较高浓度时，它会抑制 TRH 和 TSH 的分泌，从而减少生成。如果甲状腺素水平下降，这种抑制就会被解除，分泌量重新增加。
A lack of dietary iodine can lead to an underactive thyroid (hypothyroidism), causing tiredness, weight gain and a goitre, because the pituitary keeps releasing TSH in an attempt to stimulate the thyroid. Overactive thyroid (hyperthyroidism) results in an abnormally high metabolic rate, weight loss and anxiety.
饮食中缺碘可能导致甲状腺功能减退（甲减），引起疲劳、体重增加和甲状腺肿，这是因为垂体持续释放 TSH 试图刺激甲状腺。甲状腺功能亢进（甲亢）则导致代谢率异常升高、体重减轻和焦虑。
7. The Adrenal Glands and Adrenaline | 肾上腺与肾上腺素
The adrenal glands sit above each kidney. The inner region, the adrenal medulla, secretes adrenaline in response to stress or excitement. This hormone prepares the body for the ‘fight‑or‑flight’ response.
肾上腺位于两侧肾脏的上方。其内部区域——肾上腺髓质，会在应激或兴奋状态时分泌肾上腺素。这种激素使身体为“战斗或逃跑”反应做好准备。
When the sympathetic nervous system detects a threat, the adrenal medulla releases adrenaline into the blood. Adrenaline binds to receptors on target organs and triggers several effects: heart rate and blood pressure increase, breathing rate rises, airways widen, blood flow is redirected away from the skin and digestive system towards the skeletal muscles, and the liver breaks down glycogen to release glucose for a rapid energy supply. Pupils also dilate to improve vision.
当交感神经系统察觉到威胁时，肾上腺髓质将肾上腺素释放入血。肾上腺素与靶器官上的受体结合，引发多种效应：心率和血压升高、呼吸加快、气道扩张、血流从皮肤和消化系统转向骨骼肌，同时肝脏分解糖原释放葡萄糖以快速供能。瞳孔也会放大以改善视力。
These responses happen very rapidly because the adrenal medulla is directly innervated by sympathetic nerves. Once the threat passes, the nervous system returns to a resting state and adrenaline levels fall.
这些反应发生得非常迅速，因为肾上腺髓质直接受交感神经支配。一旦威胁消失，神经系统恢复静息状态，肾上腺素水平随之下降。
8. The Pituitary Gland: The Master Gland | 垂体：内分泌之王
The pituitary gland at the base of the brain is often called the ‘master gland’ because it produces hormones that regulate many other glands. The anterior lobe produces FSH (follicle‑stimulating hormone), LH (luteinising hormone), TSH, growth hormone and ACTH. The posterior lobe stores and releases ADH and oxytocin, which are made by the hypothalamus.
位于脑底部的垂体常被称为“主宰腺”，因为它产生的激素调节着许多其他腺体。垂体前叶分泌促卵泡激素（FSH）、黄体生成素（LH）、TSH、生长激素和促肾上腺皮质激素。垂体后叶储存并释放由下丘脑合成的抗利尿激素和催产素。
In the context of WJEC, key hormones to remember are FSH and LH for their roles in the menstrual cycle, TSH for thyroxine control, and ADH for water balance. The hypothalamus links the nervous and endocrine systems by secreting releasing hormones that control the anterior pituitary.
在 WJEC 考试中，需要牢记的关键激素是：FSH 和 LH 在月经周期中的作用、TSH 对甲状腺素的控制，以及 ADH 对水分平衡的调节。下丘脑通过分泌释放激素来调控垂体前叶，从而将神经系统和内分泌系统连接起来。
9. The Menstrual Cycle Hormones | 月经周期激素
The menstrual cycle lasts approximately 28 days and involves four key hormones: FSH (released from the pituitary), oestrogen (from the developing follicle), LH (from the pituitary), and progesterone (from the corpus luteum after ovulation). Their interplay relies on both negative and positive feedback.
月经周期大约持续 28 天，涉及四种关键激素：FSH（由垂体分泌）、雌激素（由发育中的卵泡分泌）、LH（由垂体分泌）和孕酮（排卵后由黄体分泌）。它们的相互作用既包含负反馈，也包含正反馈。
At the start of the cycle, the pituitary secretes FSH, which stimulates a follicle to mature in an ovary. As the follicle grows, it produces oestrogen. Oestrogen causes the lining of the uterus (endometrium) to thicken and, at moderate levels, it inhibits FSH release via negative feedback. However, once oestrogen reaches a high peak around day 13, it switches to positive feedback, triggering a massive surge of LH from the pituitary. The LH surge induces ovulation at about day 14.
在周期开始时，垂体分泌 FSH，刺激卵巢中的一个卵泡发育成熟。随着卵泡生长，它产生雌激素。雌激素促使子宫内膜增厚；在中等浓度下，雌激素通过负反馈抑制 FSH 的释放。然而，当雌激素在周期第 13 天左右达到高峰时，它会转为正反馈，触发垂体大量分泌 LH。LH 的激增在第 14 天左右引发排卵。
After ovulation, the ruptured follicle transforms into a corpus luteum, which secretes progesterone. Progesterone maintains the thick, blood‑rich endometrium, preparing it for possible implantation. It also inhibits FSH and LH release, preventing further eggs from maturing during the same cycle. If fertilisation does not occur, the corpus luteum breaks down, progesterone levels drop, and the endometrium is shed during menstruation. Then the cycle begins again.
排卵后，破裂的卵泡转变为黄体，分泌孕酮。孕酮维持子宫内膜厚实且血流丰富，为可能的着床做好准备。同时它抑制 FSH 和 LH 的释放，防止在同一周期内再有卵子成熟。若未发生受精，黄体就会退化，孕酮水平下降，子宫内膜在月经期间脱落。随后周期重新开始。
10. Controlling Fertility | 控制生育
Hormones can be used both to prevent pregnancy (contraception) and to treat infertility. The combined oral contraceptive pill contains low doses of oestrogen and progesterone. Taking the pill daily maintains high levels of these hormones, which strongly inhibit FSH secretion from the pituitary. Without FSH, no follicle matures and ovulation does not occur. The pill is typically taken for 21 days, followed by a 7‑day break during which a withdrawal bleed mimics a period.
激素既可以用于避孕，也可以用于治疗不孕。复方口服避孕药含有低剂量的雌激素和孕酮。每天服药会使这两种激素持续保持在较高水平，从而强烈抑制垂体分泌 FSH。没有了 FSH，就不会有卵泡成熟，也不会发生排卵。避孕药通常服用 21 天，然后停药 7 天，期间发生撤退性出血，模拟月经。
Progesterone‑only pills and contraceptive implants work mainly by thickening cervical mucus and thinning the endometrium, making it harder for sperm to enter and for an embryo to implant. Emergency hormonal contraception (the ‘morning‑after pill’) contains a high dose of progesterone that can delay ovulation if taken soon after unprotected sex.
单纯孕酮避孕药和皮下植入物主要通过增稠宫颈黏液并减薄子宫内膜来发挥作用，使精子难以进入，胚胎也难以着床。紧急激素避孕（“左炔诺孕酮”）含有高剂量的孕酮，在无保护性行为后尽早服用，可以推迟排卵。
For treating infertility, women who do not ovulate regularly can be given FSH and LH injections. FSH stimulates the development of multiple follicles, and an LH injection triggers their release — a technique used before in vitro fertilisation (IVF). Careful monitoring is needed to avoid multiple pregnancies and ovarian hyperstimulation syndrome.
对于治疗不孕症，排卵不规律的女性可以注射 FSH 和 LH。FSH 刺激多个卵泡发育，而 LH 则触发排卵——这是体外受精（IVF）前使用的方法。需要密切监测，以避免多胎妊娠和卵巢过度刺激综合征。
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