📚 GCSE Edexcel Biology: The Endocrine System | GCSE Edexcel 生物：内分泌系统 考点精讲
The endocrine system is a collection of glands that secrete hormones directly into the bloodstream. These chemical messengers travel to target organs, where they trigger specific responses. Unlike the nervous system, hormonal responses are slower but longer-lasting. For Edexcel GCSE Biology, you need to master the principal glands, the hormones they produce, and how feedback loops maintain internal balance. This revision guide covers everything from blood glucose control to plant tropisms.
内分泌系统是一系列将激素直接释放到血液中的腺体。这些化学信使随血液到达靶器官，并引发特定反应。与神经系统相比，激素的响应速度较慢，但作用更持久。在 Edexcel GCSE 生物学考试中，你需要掌握主要腺体、它们分泌的激素，以及反馈回路如何维持体内平衡。本复习指南涵盖从血糖调控到植物向性运动的全部考点。
1. Introduction to the Endocrine System | 内分泌系统简介
The endocrine system works alongside the nervous system to coordinate body functions. It uses hormones, which are chemical molecules (often proteins or steroids), produced by endocrine glands. These glands are ductless, meaning they pour their secretions directly into the blood. Key glands include the pituitary, thyroid, pancreas, adrenal glands, ovaries and testes.
内分泌系统与神经系统协同工作，协调身体功能。它通过激素发挥作用，激素是由内分泌腺分泌的化学分子（通常是蛋白质或类固醇）。这些腺体属于无管腺，意味着它们将分泌物直接排入血液。主要腺体包括垂体、甲状腺、胰腺、肾上腺、卵巢和睾丸。
Each hormone only affects specific target cells that possess complementary receptors on their cell membranes or inside the cytoplasm. Once the hormone binds, it triggers a chain of events that changes the cell’s activity. The blood transports hormones to all parts of the body, but only the target tissues respond.
每种激素只作用于特定的靶细胞，这些细胞在细胞膜上或细胞质内具有互补受体。激素一旦结合，就会触发一连串反应，改变细胞的活动。血液将激素运送到全身各处，但只有靶组织才会产生应答。
2. Glands and Hormones | 腺体与激素
Several glands must be memorised for the exam. The pituitary gland in the brain secretes growth hormone, anti-diuretic hormone (ADH), and hormones that control other glands. The thyroid in the neck produces thyroxine, which regulates metabolism. The pancreas (both an endocrine and exocrine organ) contains the islets of Langerhans that release insulin and glucagon. The adrenal glands sit atop the kidneys and release adrenaline. The ovaries produce oestrogen and progesterone; the testes produce testosterone.
考试中需要记住多个腺体。脑部的垂体分泌生长激素、抗利尿激素（ADH）以及控制其他腺体的激素。颈部的甲状腺产生甲状腺素，调节新陈代谢。胰腺（兼有内分泌和外分泌功能）中的胰岛释放胰岛素和胰高血糖素。肾上腺位于肾脏上方，分泌肾上腺素。卵巢分泌雌激素和孕酮；睾丸分泌睾酮。
Hormone molecules can be classified as amino acid derivatives, peptides, or steroids. Adrenaline and thyroxine are derived from amino acids; insulin is a peptide; oestrogen and testosterone are steroids. Steroid hormones can pass through the cell membrane, binding to receptors inside the cell, whereas peptide hormones bind to receptors on the cell surface.
激素分子可分为氨基酸衍生物、肽类或类固醇。肾上腺素和甲状腺素来源于氨基酸；胰岛素是一种肽；雌激素和睾酮是类固醇。类固醇激素能穿过细胞膜，与细胞内的受体结合，而肽类激素则与细胞表面的受体结合。
3. The Master Gland: Pituitary Gland | 主腺体：垂体
The pituitary gland is often called the ‘master gland’ because it secretes a range of hormones that in turn regulate other endocrine glands. For instance, thyroid-stimulating hormone (TSH) prompts the thyroid to release thyroxine. Follicle-stimulating hormone (FSH) and luteinising hormone (LH) control the ovaries and testes. The pituitary also produces ADH, which controls the water content of the blood by acting on the kidneys.
垂体常被称为“主腺体”，因为它分泌多种激素，进而调节其他内分泌腺。例如，促甲状腺激素（TSH）促使甲状腺释放甲状腺素。促卵泡激素（FSH）和黄体生成素（LH）调控卵巢和睾丸。垂体还产生抗利尿激素（ADH），通过作用于肾脏调控血液中的水分含量。
The posterior pituitary stores and releases hormones produced by the hypothalamus, including ADH and oxytocin. The anterior lobe produces and secretes its own hormones such as growth hormone, TSH, FSH and LH. This arrangement shows the close interaction between the nervous and endocrine systems.
垂体后叶储存并释放由下丘脑产生的激素，包括抗利尿激素和催产素。前叶则产生并分泌自身激素，如生长激素、TSH、FSH 和 LH。这种结构体现了神经系统与内分泌系统之间的密切配合。
4. Blood Glucose Regulation: Insulin and Glucagon | 血糖调节：胰岛素与胰高血糖素
Blood glucose concentration must be kept within a narrow range. After a meal rich in carbohydrates, the blood glucose level rises. This is detected by the pancreas, which releases insulin from its β cells. Insulin stimulates the liver and muscle cells to absorb glucose and convert it into glycogen for storage. It also increases the rate of glucose breakdown in cells for respiration.
血糖浓度必须维持在较窄的范围内。进食富含碳水化合物的膳食后，血糖水平升高。胰腺检测到这一变化，由其 β 细胞释放胰岛素。胰岛素刺激肝细胞和肌细胞摄取葡萄糖，并将其转化为糖原储存起来。它还能加快细胞中用于呼吸的葡萄糖分解速率。
When blood glucose falls — for example, during strenuous exercise — the pancreas detects the drop and its α cells secrete glucagon. Glucagon prompts the liver to convert stored glycogen back into glucose and release it into the blood. This negative feedback loop keeps the blood glucose level at around 90 mg per 100 cm³.
当血糖下降——例如在剧烈运动时——胰腺检测到这一下降，其 α 细胞便分泌胰高血糖素。胰高血糖素促使肝脏将储存的糖原重新转化为葡萄糖，并释放到血液中。这一负反馈回路将血糖水平维持在约 90 毫克/100 立方厘米。
Blood glucose high → Insulin released → Glucose → Glycogen → Blood glucose falls
Blood glucose low → Glucagon released → Glycogen → Glucose → Blood glucose rises
血糖高 → 释放胰岛素 → 葡萄糖 → 糖原 → 血糖下降
血糖低 → 释放胰高血糖素 → 糖原 → 葡萄糖 → 血糖升高
5. Type 1 and Type 2 Diabetes | 1 型和 2 型糖尿病
Diabetes mellitus is a condition in which the blood glucose control mechanism fails. In Type 1 diabetes, the body’s immune system attacks the pancreatic β cells, so little or no insulin is produced. It typically develops in childhood and is managed with insulin injections, a carefully controlled diet, and regular blood glucose monitoring. Insulin cannot be taken as a tablet because it is a protein that would be digested in the stomach.
糖尿病是血糖调控机制失效的一种疾病。在 1 型糖尿病中，人体免疫系统攻击胰腺 β 细胞，因此只产生极少甚至不产生胰岛素。它通常在儿童期发病，通过注射胰岛素、严格控制饮食和定期监测血糖来管理。胰岛素不能制成片剂服用，因为它是一种蛋白质，会被胃消化。
Type 2 diabetes is more common and often linked to obesity, lack of exercise, and ageing. In this type, the body still produces insulin, but the target cells become resistant to its effects. The pancreas may try to compensate by producing extra insulin, but eventually the β cells may become exhausted. Management focuses on a balanced diet, regular physical activity, and sometimes medication that improves insulin sensitivity or reduces glucose absorption.
2 型糖尿病更常见，通常与肥胖、缺乏运动和年龄增长有关。在此类型中，身体仍能产生胰岛素，但靶细胞对其作用产生抵抗。胰腺可能试图通过产生额外胰岛素来代偿，但最终 β 细胞可能衰竭。治疗重点在于均衡饮食、定期体育活动，有时也使用提高胰岛素敏感性或减少葡萄糖吸收的药物。
Untreated diabetes can lead to dangerously high blood glucose levels, causing damage to blood vessels, nerves, kidneys and eyes. Correlation studies show that a sedentary lifestyle and high-sugar diet increase the risk of Type 2 diabetes, though exact causal mechanisms involve multiple genes and environmental factors.
未经治疗的糖尿病可导致危险的高血糖水平，损害血管、神经、肾脏和眼睛。相关性研究表明，久坐生活方式和高糖饮食会增加 2 型糖尿病的风险，但确切的因果机制涉及多个基因和环境因素。
6. The Thyroid Gland and Metabolism | 甲状腺与新陈代谢
The thyroid gland, located in the neck, produces the hormone thyroxine. Thyroxine contains iodine atoms and plays a crucial role in regulating the basal metabolic rate — the speed at which the body’s chemical reactions occur at rest. It also supports growth and development, especially in the brain and skeleton of children.
位于颈部的甲状腺分泌甲状腺素。甲状腺素含有碘原子，在调节基础代谢率方面起着关键作用——即身体在静息时化学反应进行的速度。它还促进生长与发育，尤其是儿童大脑和骨骼的发育。
Thyroxine levels are controlled by negative feedback. When the metabolic rate is too low, the hypothalamus secretes thyrotropin-releasing hormone (TRH), which stimulates the pituitary to release TSH. TSH then causes the thyroid to release more thyroxine. As thyroxine levels rise, they inhibit the release of TRH and TSH, stabilising the system.
甲状腺素水平受负反馈调控。当代谢率过低时，下丘脑分泌促甲状腺激素释放激素（TRH），刺激垂体释放 TSH。TSH 随后促使甲状腺释放更多甲状腺素。当甲状腺素水平升高时，又会抑制 TRH 和 TSH 的释放，使系统稳定。
Iodine deficiency can lead to an underactive thyroid (hypothyroidism) and the formation of a goitre — a swelling of the thyroid gland as it tries to trap more iodine. In contrast, an overactive thyroid (hyperthyroidism) leads to excessive weight loss, heat intolerance and a rapid heartbeat.
碘缺乏可导致甲状腺功能减退（甲减）并形成甲状腺肿——甲状腺因试图捕捉更多碘而肿大。相反，甲状腺功能亢进（甲亢）会导致体重过度下降、怕热和心跳加快。
7. The Adrenal Glands and Fight or Flight | 肾上腺与“战斗或逃跑”
The adrenal glands are situated just above each kidney. Each gland has an outer cortex and an inner medulla. The medulla secretes adrenaline, a hormone that prepares the body for ‘fight or flight’ in response to stressful or dangerous situations. The brain detects fear or stress and sends impulses via sympathetic nerves to the adrenal medulla, triggering adrenaline release.
肾上腺位于两侧肾脏的上方。每个腺体由外层的皮质和内层的髓质组成。髓质分泌肾上腺素，这种激素让身体在面对压力或危险情况时做好“战斗或逃跑”的准备。大脑检测到恐惧或压力，通过交感神经向肾上腺髓质发送神经冲动，引发肾上腺素释放。
Adrenaline increases the heart rate and stroke volume, raising blood pressure and delivering more oxygen and glucose to the muscles and brain. It dilates air passages in the lungs, boosts the breakdown of glycogen to glucose in the liver, and diverts blood flow away from the digestive system and skin. Pupils dilate to improve vision, and mental alertness sharpens. All these changes occur within seconds, demonstrating the close interplay between the nervous and endocrine systems.
肾上腺素加快心率和每搏输出量，升高血压，为肌肉和大脑输送更多氧气和葡萄糖。它扩张肺部的气道，加速肝脏中糖原分解为葡萄糖，并使血液从消化系统和皮肤分流。瞳孔扩大以改善视力，头脑更加警觉。所有这一切变化都在数秒内发生，体现了神经系统与内分泌系统的紧密配合。
8. Human Reproductive Hormones | 人类生殖激素
The sex hormones drive puberty and reproduction. In males, the testes secrete testosterone, which stimulates the development of male secondary sexual characteristics such as a deeper voice, facial hair and muscle growth. In females, the ovaries produce oestrogen and progesterone. Oestrogen is responsible for female secondary sexual characteristics, including breast development and widening of the hips, and it also plays a key role in the menstrual cycle.
性激素驱动青春期和生殖。在男性体内，睾丸分泌睾酮，刺激男性第二性征的发育，例如声音变低沉、生长胡须和肌肉增长。在女性体内，卵巢分泌雌激素和孕酮。雌激素负责女性第二性征，包括乳房发育和髋部变宽，而且在月经周期中起关键作用。
The pituitary gland releases FSH and LH. In women, FSH stimulates the maturation of an egg follicle in the ovary, and LH triggers ovulation — the release of a mature egg. In men, FSH and LH stimulate sperm production and testosterone secretion, respectively.
垂体释放 FSH 和 LH。在女性体内，FSH 刺激卵巢中卵泡的成熟，LH 触发排卵——即成熟卵子的释放。在男性体内，FSH 和 LH 分别刺激精子的产生和睾酮的分泌。
9. The Menstrual Cycle and Hormonal Control | 月经周期与激素调控
The menstrual cycle typically lasts about 28 days and is regulated by the interplay of four hormones. Days 1–5: menstruation occurs; the uterus lining breaks down. FSH from the pituitary begins to rise, stimulating a follicle to develop. The developing follicle secretes oestrogen, which causes the uterus lining to thicken. As oestrogen levels peak, it triggers a surge in LH (positive feedback), which brings about ovulation around day 14.
月经周期通常持续约 28 天，由四种激素的相互作用来调节。第 1–5 天：月经来潮；子宫内膜脱落。垂体分泌的 FSH 开始升高，刺激卵泡发育。发育中的卵泡分泌雌激素，使子宫内膜增厚。当雌激素水平达到峰值时，它触发 LH 的激增（正反馈），进而在第 14 天左右引起排卵。
After ovulation, the ruptured follicle transforms into the corpus luteum, which secretes progesterone. Progesterone maintains the thick, blood-rich uterus lining in readiness for the implantation of a fertilised egg. If fertilisation does not occur, the corpus luteum breaks down, progesterone and oestrogen levels fall, and the lining is shed — marking the start of the next cycle.
排卵后，已破裂的卵泡转变为黄体，分泌孕酮。孕酮维持着厚实、富含血液的子宫内膜，为受精卵的着床做好准备。如果未发生受精，黄体退化，孕酮和雌激素水平下降，内膜脱落——标志着下一周期的开始。
Understanding these hormone interactions is essential. FSH stimulates oestrogen production; oestrogen stimulates the LH surge; LH triggers ovulation; progesterone maintains the lining. The cycle is a classic example of both negative and positive feedback in the endocrine system.
理解这些激素的相互作用至关重要。FSH 刺激雌激素生成；雌激素刺激 LH 激增；LH 触发排卵；孕酮维持子宫内膜。该周期是内分泌系统中负反馈和正反馈的经典范例。
10. Contraception and Assisted Reproductive Technology | 避孕与辅助生殖技术
Hormonal contraceptives use synthetic oestrogen and/or progesterone to disrupt the menstrual cycle. The combined oral contraceptive pill contains oestrogen and progesterone, which inhibit FSH and LH release, preventing follicle development and ovulation. The progesterone-only pill works mainly by thickening the cervical mucus, blocking sperm entry. Other methods include the contraceptive patch, implant and injection, which slowly release hormones to provide long-term contraception.
激素类避孕药使用合成雌激素和/或孕酮来干扰月经周期。复方口服避孕药含有雌激素和孕酮，它们抑制 FSH 和 LH 的释放，防止卵泡发育和排卵。仅含孕酮的避孕药主要通过增厚宫颈粘液，阻止精子进入。其他方法包括避孕贴片、皮下植入物和注射剂，它们缓慢释放激素，提供长期避孕。
Barrier methods, such as condoms and diaphragms, physically prevent sperm from reaching the egg. Unlike hormonal methods, they do not affect the hormonal cycle, and condoms also offer protection against sexually transmitted infections (STIs). Intrauterine devices (IUDs) can release copper or hormones to prevent implantation.
屏障避孕法，如安全套和子宫帽，通过物理方式阻止精子与卵子相遇。与激素法不同，它们不影响激素周期，安全套还能预防性传播感染（STIs）。宫内节育器（IUD）可释放铜或激素，以防止受精卵着床。
When couples struggle to conceive, assisted reproductive technology (ART) can help. The most common is in vitro fertilisation (IVF). FSH and LH are given to the woman to stimulate multiple eggs to mature. The eggs are collected and fertilised with sperm in the laboratory. One or two healthy embryos are then transferred to the uterus. IVF success rates decline with maternal age, and the treatment raises ethical considerations about embryo selection and multiple births.
当夫妇难以受孕时，辅助生殖技术（ART）可以提供帮助。最常见的是体外受精（IVF）。先给女方使用 FSH 和 LH，刺激多个卵子成熟。取出卵子后在实验室里与精子受精。接着将一个或两个健康胚胎移植到子宫里。IVF 的成功率随着母体年龄增长而下降，这种治疗也引发了关于胚胎选择和多胎妊娠的伦理考量。
11. Plant Hormones: Auxins and Tropisms | 植物激素：生长素与向性
Plants do not have a nervous system, but they respond to stimuli using hormones. Auxins are a group of plant hormones, with indole-3-acetic acid (IAA) being the most important. Auxins are produced in the shoot tip and control phototropism — growth towards light — and gravitropism (geotropism) — growth in response to gravity.
植物没有神经系统，但它们利用激素对环境刺激做出反应。生长素是一类植物激素，其中吲哚-3-乙酸（IAA）最为重要。生长素在茎尖产生，控制向光性——向光生长——以及向地性——响应重力的生长。
When a shoot receives unilateral light, auxin moves to the shaded side, causing cells there to elongate more than those on the illuminated side. This uneven growth bends the shoot towards the light, maximising photosynthesis. In roots, higher concentrations of auxin actually inhibit cell elongation, so the root bends away from the light.
当芽受到单侧光照时，生长素向背光侧移动，导致背光侧的细胞比向光侧的细胞伸长更多。这种不均匀的生长使茎弯向光源，最大限度地增加光合作用。在根中，较高浓度的生长素反而抑制细胞伸长，因此根会向远离光的方向弯曲。
In gravitropism, when a root is placed horizontally, auxin accumulates on the lower side due to gravity. In roots, this higher auxin concentration inhibits cell elongation, so the upper side grows faster, causing the root to bend downwards. In shoots, the higher auxin on the lower side stimulates elongation, so the shoot bends upwards against gravity.
在向地性中，当根水平放置时，由于重力作用，生长素在根部下方积累。在根中，这一较高的生长素浓度会抑制细胞伸长，因此上方生长较快，导致根向下弯曲。在茎中，下方浓度较高的生长素促进伸长，因此茎向上弯曲，对抗重力。
Investigations using agar blocks and mica sheets confirm the role of auxin in coleoptiles (shoots). Removing the tip stops phototropism; replacing the tip or placing an agar block containing auxin restores it. Light-blocking caps on the tip also prevent the response, proving that the tip is both the sensor and the hormone source.
用琼脂块和云母片进行的实验证实了生长素在胚芽鞘（芽）中的作用。摘除尖端后向光性停止；重新放回尖端或放置含有生长素的琼脂块可恢复向光性。给尖端戴上不透光的小帽也会阻止这种反应，证明尖端既是感受器也是激素来源。
12. Comparing Nervous and Hormonal Control | 神经调控与激素调控的比较
For the Edexcel exam, you must be able to compare the nervous and endocrine communication systems. Nervous communication uses electrical impulses carried along specialised neurones. The signal is extremely fast, with responses in milliseconds, but the effects are short-lived. Neurotransmitters cross synapses to deliver the message directly to a specific target cell.
Edexcel 考试要求你能够比较神经系统与内分泌系统的通讯方式。神经通讯利用通过特化神经元传导的电冲动。信号传递极快，在毫秒内做出反应，但效果短暂。神经递质越过突触，将信息直接传递给特定的靶细胞。
Hormonal communication uses chemical messengers transported in the blood. It is slower — seconds, hours or even days — but the effects can be long-lasting. Hormones are distributed throughout the body, but only the target cells with specific receptors respond. The nervous system is ideal for immediate, precise actions such as a reflex, while the endocrine system is suited for long-term processes like growth, reproduction and metabolism.
激素通讯使用通过血液运输的化学信使。速度较慢——数秒、数小时甚至数天——但效果可能持久。激素被输送到全身各处，但只有携带特异性受体的靶细胞才会做出应答。神经系统适合即时、精准的动作，如反射；而内分泌系统则适合长期过程，如生长、生殖和新陈代谢。
Below is a quick comparison table. Both systems are vital for maintaining homeostasis and often work together — for instance, the hypothalamus bridges the two systems, and adrenaline release is triggered by nerve impulses.
下方是一个快速对比表。两个系统对于维持体内平衡都至关重要，并且经常协同工作——例如，下丘脑连接着两个系统，肾上腺素的分泌就是由神经冲动触发的。
| Feature | Nervous System | Endocrine System |
|---|---|---|
| Messenger | Electrical impulses & neurotransmitters | Hormones in blood |
| Speed | Very fast (milliseconds) | Slower (seconds to days) |
| Duration | Short-lived | Long-lasting |
| Target | Specific cells (muscles, glands) | Cells with specific receptors |
| Pathway | Via neurones | Via bloodstream |
特征比较表也可用中文概括：神经信号快而短，激素信号慢而长；神经作用于特定靶点，激素随血液遍布全身。
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