High School Biology

Homeostasis稳态

Living organisms maintain a stable internal environment despite constantly changing external conditions. This guide builds from the core concept of homeostasis and feedback loops through thermoregulation, osmoregulation and the kidney, blood glucose control by insulin and glucagon, the nervous system (neurons and reflexes), the endocrine system (hormones), and the integration of neural and hormonal control into coordinated physiological responses. Worked examples and quiz questions draw on real physiology throughout.生物体在外部环境不断变化的情况下维持稳定的内环境，这一过程称为稳态（homeostasis，稳态）。本指南从稳态与反馈（feedback，反馈）回路的核心概念出发，历经体温调节（thermoregulation，体温调节）、渗透调节（osmoregulation，渗透调节）与肾脏、胰岛素（insulin，胰岛素）与胰高血糖素调节血糖（blood glucose，血糖）、神经元（neuron，神经元）与反射弧，直至激素（hormone，激素）与内分泌（endocrine，内分泌）系统，以及神经与体液调控的整合。全部例题与测验均以真实生理学情境为据。

7 sections7 节内容 US NGSS · ON · BC · ABUS NGSS · ON · BC · AB SBI4U & BC A&P 12 deeper coverage marked HonorsSBI4U 与 BC A&P 12 深度内容标为荣誉级
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How to use this guide如何使用本指南

Homeostasis is among the most tightly assessed topics in senior biology across all four curricula. The scope, however, varies significantly by grade level and course. NGSS HS-LS1-3 asks students to design and interpret investigations into feedback (conceptual, not system-by-system anatomy). Ontario SBI4U Strand E (Homeostasis) is a full anatomy-and-physiology deep-dive: named endocrine glands, named hormones, nephron anatomy, synapse chemistry, and multi-system integration. BC Anatomy and Physiology 12 is the most comprehensive of the four: all eight organ systems, negative and positive feedback, and disease as homeostatic imbalance. Alberta Biology 30 Unit A covers nervous and endocrine control in detail (action potentials, reflex arcs, endocrine gland functions, insulin/glucagon, ADH) and is a diploma-exam course. The table below locates each section in your curriculum.稳态是四套大纲中高中生物考查最紧密的主题之一，但各年级与课程的范围差异显著。NGSS HS-LS1-3 要求学生设计并解释反馈机制的探究（概念层面，非逐系统解剖）。安大略 SBI4U E 单元（稳态）是完整的解剖生理深度讲解：包括命名内分泌腺、命名激素、肾单位解剖、突触化学及多系统整合。BC 解剖与生理 12 最为全面：涵盖八大器官系统、负/正反馈，以及疾病作为稳态失衡的理解。阿尔伯塔 Biology 30 Unit A 详细讲解神经与内分泌控制（动作电位、反射弧、内分泌腺功能、胰岛素/胰高血糖素、ADH），且为文凭考试课程。下表定位各节在你大纲中的位置。

If you are in…如果你在… Focus on these sections重点学习 Defer / lighter可推迟 / 减负 Source依据
🇺🇸 US NGSS美国 NGSS §1 (feedback concept, investigation design) — HS-LS1-3 is about evidence for feedback maintaining homeostasis§1（反馈概念、探究设计）——HS-LS1-3 聚焦反馈维持稳态的证据 §3–§7 system detail: NGSS Assessment Boundary excludes cellular processes of the feedback mechanism§3–§7 系统细节：NGSS 评估边界排除反馈机制的细胞过程 NGSS HS Life Science — HS-LS1-3— HS-LS1-3
🇨🇦 ON SBI4U Honors安大略 SBI4U 荣誉 All 7 sections in full — E3.1 endocrine + excretory + nervous anatomy; E3.3 water/ionic/thermal/acid–base equilibrium; E2.1 named vocabulary (nephron, synapse, insulin)全部 7 节完整学习 — E3.1 内分泌、排泄与神经系统解剖；E3.3 水/离子/体温/酸碱平衡；E2.1 命名词汇（肾单位、突触、胰岛素） Nothing — homeostasis is a full SBI4U strand无 — 稳态是 SBI4U 完整学习单元 Ontario SBI3U/4U Biology — SBI4U Strand E E2.1, E3.1, E3.3— SBI4U E 单元 E2.1、E3.1、E3.3
🇨🇦 BC A&P 12 HonorsBC A&P 12 荣誉 All 7 sections; emphasis on negative and positive feedback (§1), organ system interrelationships (§7), disease as homeostatic imbalance (going-deeper boxes)全部 7 节；重点关注负/正反馈（§1）、器官系统相互关系（§7）、疾病作为稳态失衡（深入内容框） Nothing — homeostasis is Big Idea 1 and 3 of A&P 12无 — 稳态是 A&P 12 大概念 1 与 3 BC Life Sciences 11 / Anatomy 12 — Anatomy & Physiology 12 Big Ideas + Content— 解剖与生理 12 大概念 + 内容
🇨🇦 AB Biology 30 Honors阿尔伯塔 Biology 30 荣誉 §1 (feedback), §5 (neurons, action potentials, reflex arcs, 30–A1), §6 (endocrine glands + hormones, 30–A2), §4 (insulin/glucagon/blood glucose, 30–A2), §7 (nervous + endocrine integration)§1（反馈）、§5（神经元、动作电位、反射弧，30–A1）、§6（内分泌腺+激素，30–A2）、§4（胰岛素/胰高血糖素/血糖，30–A2）、§7（神经与内分泌整合） §3 nephron at full SBI4U depth — AB covers excretory system in Bio 20 Unit D at structural level§3 完整 SBI4U 深度肾单位 — AB 在 Bio 20 Unit D 以结构层面覆盖排泄系统 Alberta Biology 20/30 — Biology 30 Unit A GO1, GO2— Biology 30 Unit A GO1、GO2

Once you have located your row, use the two cards below for the approach that fits your timeline.找到所在行后，用下面两张卡片选择适合你时间安排的方式。

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If you are cramming the night before如果你在临阵磨枪

Know the definition of homeostasis and the difference between negative and positive feedback. Trace one complete negative feedback loop (e.g. temperature drops: thermoreceptors detect → hypothalamus signals → shivering/vasoconstriction → temperature returns to set point). Know that insulin lowers blood glucose and glucagon raises it. Read every cram-cheat box. Skip the going-deeper sections on nephron anatomy and synapse chemistry unless your course requires them.掌握稳态的定义以及负反馈与正反馈的区别。完整描述一个负反馈回路（例如体温下降：温度感受器检测 → 下丘脑发出信号 → 颤抖/血管收缩 → 体温回升至设定点）。了解胰岛素降低血糖、胰高血糖素升高血糖。阅读每个速记框，跳过肾单位解剖与突触化学的深入内容（除非课程要求）。

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If you are going for the top mark如果你目标顶分

Be precise about the three components of a feedback loop: receptor (detects stimulus), control centre (usually hypothalamus), effector (produces response). Distinguish negative feedback (corrects deviation — most homeostatic loops) from positive feedback (amplifies deviation — childbirth, blood clotting). For SBI4U and Biology 30, link each system to its mechanism: nephron tubules reabsorb water under ADH; pancreatic beta cells secrete insulin; alpha cells secrete glucagon; motor neurons relay signals via neuromuscular junctions.精准掌握反馈回路的三个组成部分：感受器（检测刺激）、控制中枢（通常为下丘脑）、效应器（产生响应）。区分负反馈（纠正偏差——大多数稳态回路）与正反馈（放大偏差——分娩、凝血）。SBI4U 与 Biology 30 轨道需将每个系统与具体机制挂钩：肾单位小管在 ADH 作用下重吸收水；胰腺 β 细胞分泌胰岛素；α 细胞分泌胰高血糖素；运动神经元通过神经肌肉接头传递信号。

Honors flag.荣誉级标记。 The going-deeper sections on nephron anatomy (§3), action potentials and synapse chemistry (§5), named endocrine glands and hormones (§6), and nervous-endocrine integration (§7) carry the Honors SBI4U or Honors A&P 12 chip. Required for Ontario SBI4U, BC Anatomy & Physiology 12, and Alberta Biology 30. If your curriculum is NGSS only, the cram-cheat boxes in §1–§4 are your core target.§3 的肾单位解剖、§5 的动作电位与突触化学、§6 的命名内分泌腺与激素，以及 §7 的神经-内分泌整合，均标注 荣誉 SBI4U 或 荣誉 A&P 12。这些内容是安大略 SBI4U、BC 解剖与生理 12 和阿尔伯塔 Biology 30 的必修内容。若你的大纲仅为 NGSS，§1–§4 的速记框是核心目标。
Section 1 · Homeostasis and feedback loops第 1 节 · 稳态与反馈回路

Homeostasis and Feedback Loops稳态与反馈回路

Homeostasis: maintaining a stable internal environment despite external change (NGSS HS-LS1-3).稳态：在外部变化的情况下维持稳定的内部环境（NGSS HS-LS1-3）。
  • Set point:设定点： the normal target value a variable is kept at (e.g. 37 °C core temperature; blood glucose ~5 mmol/L; blood pH 7.35–7.45).某变量被维持在的正常目标值（例如核心体温 37 °C；血糖约 5 mmol/L；血液 pH 7.35–7.45）。
  • Feedback loop components:反馈回路组成：
    1. Stimulus — a change in the internal environment (e.g. temperature drops).刺激 — 内环境发生变化（如体温下降）。
    2. Receptor (sensor) — detects the change (e.g. thermoreceptors in skin and hypothalamus).感受器（传感器） — 检测变化（如皮肤和下丘脑中的温度感受器）。
    3. Control centre — integrates the signal and sets the response (usually the hypothalamus or a brain centre).控制中枢 — 整合信号并设定响应（通常为下丘脑或脑中枢）。
    4. Effector — carries out the corrective response (e.g. skeletal muscles shiver; blood vessels constrict).效应器 — 执行纠正响应（如骨骼肌颤抖；血管收缩）。
  • Negative feedback:负反馈： the response opposes and reverses the original change, returning the variable to the set point. This is the dominant type in homeostasis. Example: body temperature falls → hypothalamus detects → initiates shivering and vasoconstriction → temperature rises back to 37 °C.响应与原始变化相反，将变量拉回设定点。这是稳态中的主导类型。示例：体温下降 → 下丘脑检测到 → 启动颤抖与血管收缩 → 体温回升至 37 °C。
  • Positive feedback:正反馈： the response amplifies the original change, driving it further in the same direction until a threshold is reached. Examples: uterine contractions during childbirth (oxytocin release amplifies contractions); blood clotting cascade. Positive feedback is not homeostatic — it drives the system away from the set point until a specific event terminates the loop.响应放大原始变化，将其朝同一方向进一步推进，直至达到阈值。示例：分娩时子宫收缩（催产素释放放大收缩）；血液凝固级联反应。正反馈不具稳态功能——它使系统偏离设定点，直至某一特定事件终止该回路。
Worked Example 1 · Tracing a negative feedback loop例题 1 · 描述一个负反馈回路

A student exercises vigorously and their core body temperature rises to 39 °C. Describe the negative feedback loop that returns their temperature to 37 °C, naming the receptor, control centre, and effectors involved.一名学生剧烈运动后，核心体温升至 39 °C。描述使其体温回降至 37 °C 的负反馈回路，并说明涉及的感受器、控制中枢和效应器。

Stimulus:刺激： core temperature above set point (39 °C > 37 °C).核心体温超过设定点（39 °C > 37 °C）。

Receptor:感受器： thermoreceptors in the skin (peripheral) and in the hypothalamus (central) detect the elevated temperature.皮肤（外周）和下丘脑（中枢）中的温度感受器检测到体温升高。

Control centre:控制中枢： the hypothalamus integrates the signal and activates cooling responses.下丘脑整合信号并激活降温响应。

Effectors and responses:效应器与响应： (1) Sweat glands secrete sweat — evaporation removes heat. (2) Cutaneous blood vessels dilate (vasodilation) — more blood flows near the skin surface, radiating heat. (3) Metabolic rate decreases slightly. Result: temperature falls back toward 37 °C; the loop is negative because the response (cooling) opposes the stimulus (heating).(1) 汗腺分泌汗液——蒸发散热。(2) 皮肤血管扩张（血管舒张）——更多血液流向皮肤表面，散发热量。(3) 代谢率略有下降。结果：体温回降至 37 °C；该回路为负反馈，因为响应（降温）与刺激（升温）相反。

Which of the following best defines homeostasis?下列哪项最准确地定义了稳态？
§1 · Q1
The maintenance of a stable internal environment despite changes in external conditions在外部条件变化的情况下维持稳定的内部环境
The process by which organisms adapt to their external environment over generations生物体世代适应外部环境的过程
The equal distribution of materials between two solutions across a membrane物质通过膜在两种溶液间均匀分布的过程
The regulation of gene expression in response to environmental signals响应环境信号的基因表达调控
Homeostasis is the regulation of internal conditions (temperature, pH, glucose, water, ions) to keep them within narrow limits despite external changes. It is achieved through feedback loops, not evolutionary adaptation.稳态是指在外部条件变化的情况下，将内部条件（体温、pH、葡萄糖、水、离子）维持在狭窄范围内的调节过程。它通过反馈回路实现，而非进化适应。
Homeostasis is about maintaining a stable internal environment through feedback mechanisms. It is not about evolution, osmosis, or gene regulation specifically.稳态是通过反馈机制维持稳定内环境的过程，与进化、渗透或基因调控无直接对应。
During childbirth, the hormone oxytocin stimulates uterine contractions, which in turn cause more oxytocin to be released, intensifying contractions further. This is an example of:分娩过程中，激素催产素刺激子宫收缩，子宫收缩又促使更多催产素释放，进一步加强收缩。这是以下哪种反馈的例子？
§1 · Q2
Negative feedback, because the contractions eventually stop负反馈，因为收缩最终会停止
Negative feedback, because oxytocin opposes the original change负反馈，因为催产素与原始变化相反
Positive feedback, because the response amplifies the original stimulus正反馈，因为响应放大了原始刺激
Homeostasis, because the body maintains a constant birth rate稳态，因为机体维持恒定的出生速率
Positive feedback amplifies the original change (more contraction → more oxytocin → even more contraction). The loop terminates only when the baby is born. This is not homeostatic — positive feedback drives the system away from the set point until a specific event ends the cycle.正反馈放大原始变化（更多收缩 → 更多催产素 → 更强收缩）。只有婴儿出生时，该回路才终止。这不是稳态——正反馈使系统偏离设定点，直至特定事件终止循环。
The response (more oxytocin, stronger contractions) amplifies rather than opposes the original stimulus — this is positive feedback, not negative feedback.响应（更多催产素、更强收缩）放大而非对抗原始刺激——这是正反馈，而非负反馈。
Going deeper — investigation design for HS-LS1-3: measuring feedback in action深入 — HS-LS1-3 的探究设计：测量反馈作用

NGSS HS-LS1-3 requires students to plan and conduct an investigation that provides evidence for feedback mechanisms. Good investigation designs include: (1) Heart rate response to exercise — measure resting heart rate, exercise for 3 minutes, record heart rate every 30 seconds during recovery; a graph of heart rate vs. time shows the feedback loop returning heart rate to baseline. (2) Stomate response to moisture — observe leaf surface stomata under a microscope after varying humidity; stomata close (reducing water loss) when humidity falls. (3) Root development in response to water — grow seedlings with water on one side only and observe directional root growth. In each case, identify the stimulus, the receptor, the control centre, the effector, and the measurable output that returns toward the set point.NGSS HS-LS1-3 要求学生计划并开展探究活动，为反馈机制提供证据。良好的探究设计包括：(1) 心率对运动的响应——测量静息心率，运动 3 分钟，恢复期每 30 秒记录一次心率；心率-时间图展示反馈回路将心率拉回基线。(2) 气孔对湿度的响应——在不同湿度下用显微镜观察叶片表面气孔；湿度下降时气孔关闭（减少失水）。(3) 根系对水分的响应——在种子一侧提供水分，观察根系定向生长。在每种情况下，识别刺激、感受器、控制中枢、效应器，以及向设定点回归的可测量输出。

Section 2 · Thermoregulation第 2 节 · 体温调节

Thermoregulation体温调节

Thermoregulation: keeping core temperature near 37 °C via negative feedback (BC A&P 12; SBI4U E3.3; Biology 30 A1).体温调节：通过负反馈将核心体温维持在 37 °C 附近（BC A&P 12；SBI4U E3.3；Biology 30 A1）。
  • Ectotherms vs endotherms:外温动物与内温动物： ectotherms (reptiles, fish) regulate body temperature using external heat sources; endotherms (mammals, birds) generate heat internally through metabolism and regulate it via physiological mechanisms.外温动物（爬行动物、鱼类）利用外部热源调节体温；内温动物（哺乳动物、鸟类）通过代谢产生热量，并通过生理机制进行调节。
  • Control centre:控制中枢： the hypothalamus monitors blood temperature and skin thermoreceptors, then coordinates responses.下丘脑监控血液温度和皮肤温度感受器，并协调相应响应。
  • Too hot — cooling responses:体温过高——降温响应：
    • Sweating: evaporation removes latent heat from the skin surface.出汗：蒸发带走皮肤表面的潜热。
    • Vasodilation: cutaneous blood vessels widen, bringing more warm blood to the surface to radiate heat.血管舒张：皮肤血管扩张，将更多温血带到体表散热。
    • Reduced metabolic rate; behavioural changes (seeking shade).代谢率降低；行为改变（寻找阴凉处）。
  • Too cold — warming responses:体温过低——升温响应：
    • Shivering: involuntary skeletal muscle contractions generate heat.颤抖：不随意骨骼肌收缩产生热量。
    • Vasoconstriction: cutaneous blood vessels narrow, shunting blood away from the surface to reduce heat loss.血管收缩：皮肤血管收窄，将血液从体表分流，减少热量散失。
    • Piloerection (goosebumps): arrector pili muscles raise hair to trap an insulating air layer.竖毛（鸡皮疙瘩）：竖毛肌收缩使毛发竖立，形成隔热空气层。
    • Increased metabolic rate; behavioural changes (seeking warmth).代谢率升高；行为改变（寻找温暖场所）。
Worked Example 2 · Vasodilation and heat loss例题 2 · 血管舒张与热量散失

A marathon runner's core temperature rises to 40 °C. Explain how vasodilation helps restore temperature to 37 °C, and why this response is classified as negative feedback.一名马拉松运动员的核心体温升至 40 °C。解释血管舒张如何帮助将体温恢复至 37 °C，以及为何该响应被归类为负反馈。

Mechanism:机制： The hypothalamus detects blood temperature above 37 °C and signals smooth muscle in cutaneous arterioles to relax (vasodilate). More blood flows through capillaries close to the skin surface. Heat is transferred from the blood to the skin and lost to the environment by radiation and convection. Sweat glands are also activated; evaporation of sweat removes additional heat.下丘脑检测到血液温度超过 37 °C，并向皮肤小动脉的平滑肌发出信号，使其舒张（血管扩张）。更多血液流经靠近皮肤表面的毛细血管。热量从血液转移到皮肤，并通过辐射和对流散失到环境中。汗腺同时被激活；汗液蒸发带走额外热量。

Why negative feedback:为何为负反馈： the response (heat loss via vasodilation and sweating) opposes the original change (temperature rise), returning the variable toward the set point. Once temperature drops to 37 °C, the hypothalamus reduces the cooling signals — this is the hallmark of negative feedback.响应（通过血管舒张与出汗散热）与原始变化（体温升高）相反，将变量拉回设定点。一旦体温降至 37 °C，下丘脑便减少降温信号——这是负反馈的标志性特征。

When a person moves from a warm room into cold air, their skin blood vessels constrict. What is the homeostatic purpose of this response?当一个人从温暖的房间进入冷空气时，皮肤血管收缩。这一响应的稳态目的是什么？
§2 · Q1
To increase blood flow to the skin to warm it增加皮肤血流量以使其变暖
To reduce heat loss from the body surface and maintain core temperature减少体表热量散失，维持核心体温
To lower blood pressure in response to cold响应寒冷而降低血压
To trigger sweating to cool the body触发出汗以冷却身体
Vasoconstriction reduces blood flow near the skin surface, limiting heat transfer from warm blood to cold air. This conserves core body heat and is part of the negative feedback loop opposing the drop in body temperature.血管收缩减少皮肤表面附近的血流量，限制温血向冷空气的热量传递。这有助于保存核心体热，是对抗体温下降的负反馈回路的一部分。
Vasoconstriction reduces, not increases, blood flow to the skin surface. This reduces heat radiation to the cold environment, helping maintain core temperature.血管收缩减少而非增加皮肤表面的血流量。这减少了向冷环境的热量辐射，有助于维持核心体温。
Going deeper — fever as a disruption of the thermostat set point (SBI4U; BC A&P 12)深入 — 发烧作为温度调定点的改变（SBI4U；BC A&P 12）

Fever is not a failure of homeostasis — it is a controlled upward shift of the hypothalamic set point, triggered by pyrogens (fever-producing substances, e.g. bacterial lipopolysaccharides or cytokines released by immune cells). When pyrogens raise the set point to, say, 39 °C, the body's normal temperature of 37 °C now feels "cold" to the hypothalamus, which triggers warming responses (shivering, vasoconstriction) until the new set point is reached. When pyrogens are cleared, the set point drops back to 37 °C and the body feels hot at 39 °C, triggering sweating and vasodilation to cool down. This explains why patients often feel cold (chills) as a fever rises, and sweaty as it breaks. Fever can be adaptive: higher temperatures inhibit pathogen replication and enhance immune cell activity.发烧并非稳态的失败——它是下丘脑调定点受控地上移，由致热原（产热物质，如细菌脂多糖或免疫细胞释放的细胞因子）触发。当致热原将调定点提高至 39 °C 时，机体正常体温 37 °C 在下丘脑看来感觉"偏低"，从而触发升温响应（颤抖、血管收缩），直至达到新的调定点。当致热原被清除后，调定点回落至 37 °C，此时 39 °C 对机体来说感觉过热，触发出汗和血管舒张以降温。这解释了为何患者常在体温升高时感到发冷（寒战），而在体温退热时出汗。发烧具有适应意义：较高的温度可抑制病原体复制并增强免疫细胞活性。

Section 3 · Osmoregulation and the kidney第 3 节 · 渗透调节与肾脏

Osmoregulation and the Kidney渗透调节与肾脏

Osmoregulation: maintaining water and ion balance (SBI4U E3.3; BC A&P 12; Biology 20 Unit D GO3).渗透调节：维持水分和离子平衡（SBI4U E3.3；BC A&P 12；Biology 20 Unit D GO3）。
  • Why it matters:为何重要： cells are surrounded by extracellular fluid. If blood becomes too concentrated (hypertonic), cells lose water by osmosis and shrink. If blood becomes too dilute (hypotonic), cells gain water and may swell or burst. Kidneys maintain blood osmolarity within a narrow range (~285–295 mOsm/kg).细胞被细胞外液包围。若血液变得过浓（高渗），细胞通过渗透失水并收缩。若血液变得过稀（低渗），细胞吸水，可能膨胀或破裂。肾脏将血液渗透压维持在狭窄范围内（约 285–295 mOsm/kg）。
  • The nephron — functional unit of the kidney:肾单位 — 肾脏的功能单位：
    • Glomerulus + Bowman's capsule: blood is filtered under pressure; water, glucose, ions, urea pass into the filtrate; blood cells and proteins stay behind.肾小球 + 鲍曼囊：血液在压力下被过滤；水、葡萄糖、离子、尿素进入滤液；血细胞和蛋白质留在血管中。
    • Proximal convoluted tubule: reabsorbs ~65% of filtrate (glucose, Na+, water) back into blood.近端卷曲小管：将约 65% 的滤液（葡萄糖、Na+、水）重吸收回血液。
    • Loop of Henle: creates an osmotic gradient in the medulla that drives water reabsorption in the collecting duct.亨利环：在髓质中建立渗透梯度，驱动集合管中的水重吸收。
    • Distal convoluted tubule + collecting duct: fine-tuned reabsorption of water (under ADH) and Na+ (under aldosterone); remainder becomes urine.远端卷曲小管 + 集合管：在 ADH 作用下精细调节水的重吸收，在醛固酮作用下调节 Na+ 的重吸收；余下液体成为尿液。
  • ADH:ADH（抗利尿激素）： released from the posterior pituitary when blood osmolarity rises (dehydration). ADH makes collecting duct cells more permeable to water, increasing water reabsorption and producing concentrated urine. When hydrated, ADH levels fall, ducts are less permeable, and dilute urine is produced.当血液渗透压升高（脱水）时，由垂体后叶释放。ADH 使集合管细胞对水的通透性增加，促进水的重吸收，产生浓缩尿液。当体内水分充足时，ADH 水平下降，集合管通透性降低，产生稀释尿液。
A person drinks very little water on a hot day. How will ADH levels and urine concentration change?一个人在炎热的天气中饮水很少。ADH 水平和尿液浓度将如何变化？
§3 · Q1
ADH decreases; urine becomes more concentratedADH 减少；尿液变得更浓
ADH increases; urine becomes more diluteADH 增多；尿液变得更稀
ADH decreases; urine becomes more diluteADH 减少；尿液变得更稀
ADH increases; urine becomes more concentratedADH 增多；尿液变得更浓
Dehydration raises blood osmolarity. The hypothalamus detects this and signals the posterior pituitary to release more ADH. ADH increases water reabsorption in the collecting duct, producing small volumes of concentrated urine — conserving body water. This is negative feedback: the response (water retention) opposes the stimulus (dehydration).脱水导致血液渗透压升高。下丘脑检测到这一变化，并信号传递至垂体后叶释放更多 ADH。ADH 促进集合管中水的重吸收，产生少量浓缩尿液——保留体内水分。这是负反馈：响应（水分保留）与刺激（脱水）相反。
More ADH → more water reabsorbed → more concentrated urine. Dehydration raises, not lowers, ADH levels.ADH 增多 → 水重吸收增加 → 尿液更浓。脱水使 ADH 水平升高，而非降低。
Going deeper — aldosterone and sodium regulation; dialysis as renal replacement (SBI4U E3.3; Biology 20 D3) Honors SBI4U深入 — 醛固酮与钠调节；透析作为肾替代治疗（SBI4U E3.3；Biology 20 D3）荣誉 SBI4U

Aldosterone (from the adrenal cortex) acts on the distal tubule and collecting duct to increase Na+ reabsorption. Because water follows Na+ by osmosis, this also increases water retention and raises blood pressure. The renin-angiotensin-aldosterone system (RAAS) is the key regulator: when blood pressure falls, the kidneys release renin, which converts angiotensinogen to angiotensin II, which stimulates aldosterone release. This is negative feedback on blood pressure. Dialysis replaces kidney function mechanically: hemodialysis passes blood across a semi-permeable membrane into dialysate, removing urea, excess ions, and water. Peritoneal dialysis uses the peritoneum as the membrane. SBI4U E2.1 names "dialysis" as required vocabulary.醛固酮（来自肾上腺皮质）作用于远端小管和集合管，促进 Na+ 的重吸收。由于水通过渗透跟随 Na+ 移动，这也增加了水的保留并升高血压。肾素-血管紧张素-醛固酮系统（RAAS）是关键调节机制：当血压下降时，肾脏释放肾素，肾素将血管紧张素原转化为血管紧张素 II，后者刺激醛固酮释放。这是对血压的负反馈。透析以机械方式替代肾功能：血液透析将血液通过半透膜与透析液接触，去除尿素、多余离子和水分。腹膜透析以腹膜为透析膜。SBI4U E2.1 将"透析"列为必要词汇。

Section 4 · Blood glucose regulation第 4 节 · 血糖调节

Blood Glucose Regulation: Insulin and Glucagon血糖调节：胰岛素与胰高血糖素

Blood glucose set point: ~5 mmol/L. Two antagonistic hormones from the pancreatic islets (SBI4U E3.3; Biology 30 A2; BC A&P 12).血糖设定点：约 5 mmol/L。来自胰岛的两种拮抗激素（SBI4U E3.3；Biology 30 A2；BC A&P 12）。
  • After a meal (blood glucose rises):餐后（血糖升高）：
    • Pancreatic beta cells detect the rise and secrete insulin.胰腺 β 细胞检测到血糖升高，分泌胰岛素。
    • Insulin stimulates body cells (especially liver and muscle) to take up glucose from the blood and convert it to glycogen (glycogenesis).胰岛素刺激机体细胞（尤其是肝脏和肌肉）从血液中摄取葡萄糖，并将其转化为糖原（糖原生成）。
    • Blood glucose falls back toward 5 mmol/L. Insulin secretion decreases as glucose normalizes — negative feedback.血糖回降至约 5 mmol/L。随着血糖恢复正常，胰岛素分泌减少——负反馈。
  • Between meals (blood glucose falls):餐间（血糖下降）：
    • Pancreatic alpha cells detect the drop and secrete glucagon.胰腺 α 细胞检测到血糖下降，分泌胰高血糖素。
    • Glucagon stimulates the liver to break down glycogen back into glucose (glycogenolysis) and release it into the blood.胰高血糖素刺激肝脏将糖原分解为葡萄糖（糖原分解）并释放入血液。
    • Blood glucose rises back toward 5 mmol/L. Glucagon secretion decreases — negative feedback.血糖回升至约 5 mmol/L。胰高血糖素分泌减少——负反馈。
  • Diabetes mellitus:糖尿病： Type 1 — autoimmune destruction of beta cells, no insulin produced; treated with insulin injections. Type 2 — cells become insulin-resistant; managed with diet, exercise, and/or oral medications. Both represent failures of the blood glucose homeostatic loop.1 型糖尿病——自身免疫性 β 细胞破坏，无法产生胰岛素；用胰岛素注射治疗。2 型糖尿病——细胞对胰岛素产生抵抗；通过饮食、运动和/或口服药物管理。两者均代表血糖稳态回路的失效。
Worked Example 3 · Tracing the insulin negative feedback loop例题 3 · 描述胰岛素负反馈回路

A person eats a large carbohydrate meal and their blood glucose rises to 9 mmol/L. Trace the complete negative feedback loop that returns their blood glucose to ~5 mmol/L, naming the hormone, its source, its target, and the outcome.一个人吃了大量碳水化合物，血糖升至 9 mmol/L。描述使血糖回降至约 5 mmol/L 的完整负反馈回路，并说明激素名称、来源、靶器官及结果。

Stimulus:刺激： blood glucose rises above set point (9 > 5 mmol/L).血糖超过设定点（9 > 5 mmol/L）。

Receptor & control:感受器与控制： pancreatic beta cells act as both sensor and secretor; they detect elevated glucose directly and release insulin.胰腺 β 细胞同时充当感受器和分泌器；它们直接检测血糖升高并释放胰岛素。

Hormone:激素： insulin travels in the blood to target cells (liver, muscle, adipose tissue).胰岛素随血液流向靶细胞（肝脏、肌肉、脂肪组织）。

Effector response:效应器响应： liver and muscle cells increase glucose uptake and convert glucose to glycogen (glycogenesis). Adipose cells convert glucose to fat.肝脏和肌肉细胞增加葡萄糖摄取，并将葡萄糖转化为糖原（糖原生成）。脂肪细胞将葡萄糖转化为脂肪。

Outcome:结果： blood glucose falls back to ~5 mmol/L; insulin secretion decreases (negative feedback). The loop is negative because the response (glucose removal) opposes the stimulus (glucose rise).血糖回降至约 5 mmol/L；胰岛素分泌减少（负反馈）。该回路为负反馈，因为响应（葡萄糖移除）与刺激（血糖升高）相反。

A person has not eaten for 12 hours and their blood glucose drops to 3.5 mmol/L. Which hormone is released, from which cell type, and what is its effect on the liver?一个人已 12 小时未进食，血糖降至 3.5 mmol/L。哪种激素被释放？来自哪种细胞？对肝脏有何影响？
§4 · Q1
Insulin from beta cells; stimulates glycogen synthesis in the liver来自 β 细胞的胰岛素；刺激肝脏中的糖原合成
Glucagon from alpha cells; stimulates glycogen breakdown (glycogenolysis) in the liver to release glucose来自 α 细胞的胰高血糖素；刺激肝脏中的糖原分解（糖原分解）以释放葡萄糖
Insulin from alpha cells; stimulates glucose uptake by the liver来自 α 细胞的胰岛素；刺激肝脏摄取葡萄糖
Glucagon from beta cells; inhibits glucose release from the liver来自 β 细胞的胰高血糖素；抑制肝脏释放葡萄糖
When blood glucose falls below the set point, pancreatic alpha cells secrete glucagon. Glucagon travels to the liver and stimulates glycogenolysis (glycogen → glucose) and gluconeogenesis, releasing glucose into the blood. Blood glucose rises back toward 5 mmol/L — negative feedback.当血糖低于设定点时，胰腺 α 细胞分泌胰高血糖素。胰高血糖素到达肝脏，刺激糖原分解（糖原 → 葡萄糖）和糖异生，将葡萄糖释放入血液。血糖回升至约 5 mmol/L——负反馈。
Glucagon (from alpha cells, not beta cells) responds to low blood glucose by stimulating the liver to break down glycogen. Insulin (from beta cells) responds to high blood glucose.胰高血糖素（来自 α 细胞，非 β 细胞）通过刺激肝脏分解糖原来响应低血糖。胰岛素（来自 β 细胞）响应高血糖。
A patient with Type 1 diabetes has very low blood insulin because their immune system destroyed their pancreatic beta cells. What is the most direct consequence of this?一名 1 型糖尿病患者因免疫系统破坏了胰腺 β 细胞而血液胰岛素极低。这最直接的后果是什么？
§4 · Q2
Blood glucose remains persistently high because cells cannot take up glucose without insulin signalling血糖持续偏高，因为没有胰岛素信号，细胞无法摄取葡萄糖
Blood glucose remains persistently low because glucagon is also destroyed血糖持续偏低，因为胰高血糖素也被破坏
The liver converts excess glucose to insulin directly肝脏直接将多余的葡萄糖转化为胰岛素
Blood glucose is unaffected because the kidneys take over glucose regulation血糖不受影响，因为肾脏接管了血糖调节
Insulin is required for most body cells to take up glucose from the blood. Without insulin, glucose cannot enter cells and accumulates in the blood (hyperglycemia). The homeostatic negative feedback loop for lowering blood glucose is broken. Treatment requires insulin injections to restore the effector signal.大多数机体细胞从血液中摄取葡萄糖需要胰岛素。没有胰岛素，葡萄糖无法进入细胞，在血液中积累（高血糖）。降低血糖的稳态负反馈回路被破坏。治疗需要注射胰岛素以恢复效应信号。
Without insulin, cells cannot take up glucose → blood glucose stays high (hyperglycemia). Glucagon is produced by alpha cells (a different cell type) and is typically unaffected in Type 1 diabetes.没有胰岛素，细胞无法摄取葡萄糖 → 血糖持续偏高（高血糖）。胰高血糖素由 α 细胞（不同细胞类型）产生，在 1 型糖尿病中通常不受影响。
Section 5 · Nervous control第 5 节 · 神经控制

Nervous Control: Neurons and Reflexes神经控制：神经元与反射

The nervous system provides rapid, short-duration control signals to effectors (Biology 30 A1; SBI4U E3.1; BC A&P 12).神经系统向效应器提供快速、短时的控制信号（Biology 30 A1；SBI4U E3.1；BC A&P 12）。
  • Neuron structure:神经元（神经元）结构：
    • Dendrites — receive signals from other neurons or receptors.树突 — 接收来自其他神经元或感受器的信号。
    • Cell body (soma) — integrates signals; contains nucleus and organelles.细胞体（胞体） — 整合信号；含细胞核和细胞器。
    • Axon — long process that conducts electrical signals (action potentials) away from the cell body. Myelinated axons conduct faster.轴突 — 将电信号（动作电位）从细胞体向外传导的长突起。有髓鞘轴突传导更快。
    • Synapse — the junction between two neurons. The action potential triggers release of neurotransmitters (e.g. acetylcholine) from the presynaptic terminal; they diffuse across the synaptic cleft and bind receptors on the postsynaptic cell.突触 — 两个神经元之间的连接。动作电位触发突触前末梢释放神经递质（如乙酰胆碱）；神经递质扩散穿越突触间隙，与突触后细胞上的受体结合。
  • Three neuron types:三类神经元：
    • Sensory (afferent): carry signals from receptors to the CNS.感觉（传入）神经元：将信号从感受器传至中枢神经系统（CNS）。
    • Interneurons: in the brain/spinal cord, integrate and relay signals.中间神经元：位于脑/脊髓，整合并中继信号。
    • Motor (efferent): carry signals from the CNS to effectors (muscles, glands).运动（传出）神经元：将信号从 CNS 传至效应器（肌肉、腺体）。
  • Reflex arc:反射弧： receptor → sensory neuron → interneuron (spinal cord) → motor neuron → effector. Bypasses the brain for speed — e.g. withdrawing a hand from a hot surface (withdrawal reflex) or the patellar (knee-jerk) reflex.感受器 → 感觉神经元 → 中间神经元（脊髓）→ 运动神经元 → 效应器。绕过大脑以提高速度——例如从热物体表面缩手（退缩反射）或膝跳反射。
A person touches a hot stove and immediately pulls their hand away before consciously feeling pain. Which part of the nervous system coordinates this rapid response?一个人触碰热炉后立即缩手，在有意识感受到疼痛之前。神经系统的哪个部分协调了这一快速响应？
§5 · Q1
The cerebral cortex, because it processes pain signals大脑皮层，因为它处理疼痛信号
The endocrine system via hormone release内分泌系统通过激素释放
A spinal reflex arc, which routes the signal through the spinal cord before the brain registers pain脊髓反射弧，在大脑感知疼痛之前通过脊髓传递信号
The hypothalamus, which monitors all homeostatic changes下丘脑，因为它监控所有稳态变化
A spinal reflex arc routes the signal: thermoreceptors in the skin → sensory neuron → interneuron in spinal cord → motor neuron → arm muscles contract to withdraw the hand. The signal reaches the brain a fraction of a second later (consciously felt as pain), but the protective withdrawal has already occurred. Reflex arcs are faster than brain-mediated responses because they take a shorter neural path.脊髓反射弧传递信号：皮肤热感受器 → 感觉神经元 → 脊髓中间神经元 → 运动神经元 → 手臂肌肉收缩缩手。信号在极短时间后到达大脑（有意识地感受为疼痛），但保护性缩手已经发生。反射弧比大脑介导的响应更快，因为神经路径更短。
Reflex arcs (spinal) do not require the brain — they route through the spinal cord directly. This makes the withdrawal faster than a conscious (cortex-mediated) response.反射弧（脊髓）不需要大脑——它们直接通过脊髓传递。这使缩手比有意识（皮层介导）的响应更快。
Going deeper — action potentials and synaptic transmission (Biology 30 A1; SBI4U E3.1) Honors Bio 30深入 — 动作电位与突触传递（Biology 30 A1；SBI4U E3.1）荣誉 Bio 30

At rest, a neuron maintains a resting membrane potential of about −70 mV (inside negative) due to the Na+/K+ pump maintaining more Na+ outside and more K+ inside. When a stimulus exceeds threshold, voltage-gated Na+ channels open: Na+ rushes in, depolarizing the membrane to about +30 mV (action potential). K+ channels then open, K+ flows out (repolarization), and the pump restores the resting state. The action potential is all-or-none: stimuli below threshold produce no signal; any suprathreshold stimulus produces the same size action potential. Intensity is coded by frequency of firing, not amplitude. At the synapse, the action potential triggers Ca2+ influx into the presynaptic terminal, which causes synaptic vesicles to fuse with the membrane and release neurotransmitter (e.g. acetylcholine) into the synaptic cleft. Acetylcholinesterase breaks down acetylcholine to terminate the signal (Biology 30 A1 requires students to name norepinephrine, acetylcholine, and cholinesterase).静息时，神经元因 Na+/K+ 泵维持细胞外较多 Na+ 和细胞内较多 K+，保持约 -70 mV 的静息膜电位（内负）。当刺激超过阈值时，电压门控 Na+ 通道开放：Na+ 内流，使膜去极化至约 +30 mV（动作电位）。随后 K+ 通道开放，K+ 外流（复极化），Na+/K+ 泵恢复静息状态。动作电位是全或无的：阈值以下的刺激不产生信号；任何超阈刺激均产生相同大小的动作电位。刺激强度由放电频率而非幅度编码。在突触处，动作电位触发 Ca2+ 内流进入突触前末梢，使突触小泡与膜融合并将神经递质（如乙酰胆碱）释放到突触间隙。乙酰胆碱酯酶分解乙酰胆碱以终止信号（Biology 30 A1 要求学生命名去甲肾上腺素、乙酰胆碱和胆碱酯酶）。

Section 6 · Endocrine control第 6 节 · 内分泌控制

Endocrine Control: Hormones and Glands内分泌控制：激素与腺体

The endocrine system provides slower, longer-duration signals via hormones in the blood (SBI4U E3.1; Biology 30 A2; BC A&P 12).内分泌系统通过血液中的激素（激素）提供较慢、持续时间较长的信号（SBI4U E3.1；Biology 30 A2；BC A&P 12）。
  • Hormone properties:激素特性： chemical messengers secreted by endocrine glands directly into the blood; travel to distant target organs; bind specific receptors; effect depends on the receptor, not the hormone alone.化学信使，由内分泌腺直接分泌入血液；传至远处靶器官；与特异性受体结合；效果取决于受体，而非单独的激素。
  • Key glands and hormones (Biology 30 A2; SBI4U E3.1):主要腺体与激素（Biology 30 A2；SBI4U E3.1）：
    Gland腺体Hormone(s)激素Main function主要功能
    Hypothalamus下丘脑Releasing/inhibiting hormones释放/抑制激素Controls anterior pituitary控制垂体前叶
    Anterior pituitary垂体前叶TSH, ACTH, GH, FSH, LHTSH、ACTH、GH、FSH、LHControls thyroid, adrenals, gonads, growth控制甲状腺、肾上腺、性腺、生长
    Posterior pituitary垂体后叶ADH, oxytocinADH、催产素Water reabsorption; uterine contractions水重吸收；子宫收缩
    Thyroid甲状腺Thyroxine (T4)甲状腺素（T4）Sets basal metabolic rate; needed for growth and development设定基础代谢率；生长发育所必需
    Adrenal cortex肾上腺皮质Aldosterone, cortisol醛固酮、皮质醇Na+ reabsorption; stress response; blood glucoseNa+ 重吸收；应激响应；血糖
    Adrenal medulla肾上腺髓质Adrenaline (epinephrine)肾上腺素Fight-or-flight: raises heart rate, blood glucose, blood pressure战斗或逃跑：升高心率、血糖、血压
    Pancreatic islets胰岛Insulin (β cells), glucagon (α cells)胰岛素（β 细胞）、胰高血糖素（α 细胞）Blood glucose regulation (see §4)血糖调节（见 §4）
  • Negative feedback in the endocrine system:内分泌系统中的负反馈： most endocrine axes use negative feedback. Example: low blood thyroxine → hypothalamus releases TRH → pituitary releases TSH → thyroid releases more T4 → high T4 suppresses TRH and TSH release (negative feedback). This "hypothalamic-pituitary-target gland axis" pattern repeats across the reproductive, adrenal, and thyroid systems.大多数内分泌轴使用负反馈。示例：血液甲状腺素低 → 下丘脑释放 TRH → 垂体释放 TSH → 甲状腺释放更多 T4 → 高 T4 抑制 TRH 和 TSH 释放（负反馈）。这种"下丘脑-垂体-靶腺轴"模式在生殖、肾上腺和甲状腺系统中反复出现。
A person is dehydrated. Which hormone is released, from which gland, and what does it do?一个人脱水了。哪种激素被释放？来自哪个腺体？它有什么作用？
§6 · Q1
Insulin from the pancreas; stimulates glucose uptake to restore energy来自胰腺的胰岛素；刺激葡萄糖摄取以恢复能量
Thyroxine from the thyroid; increases metabolic rate to generate heat来自甲状腺的甲状腺素；增加代谢率以产生热量
Aldosterone from the adrenal cortex; stimulates water excretion by the kidney来自肾上腺皮质的醛固酮；刺激肾脏排水
ADH from the posterior pituitary; increases water reabsorption in the kidney collecting duct来自垂体后叶的 ADH；增加肾脏集合管中水的重吸收
Dehydration raises blood osmolarity. The hypothalamus detects this and signals the posterior pituitary to release ADH (antidiuretic hormone). ADH travels to the kidney collecting duct and makes it more permeable to water, increasing reabsorption and producing concentrated urine. This conserves water and restores osmolarity to the set point — negative feedback.脱水导致血液渗透压升高。下丘脑检测到这一变化，信号传递至垂体后叶释放 ADH（抗利尿激素）。ADH 到达肾脏集合管，使其对水的通透性增加，促进重吸收，产生浓缩尿液。这有助于保存水分，将渗透压恢复至设定点——负反馈。
ADH from the posterior pituitary specifically controls water reabsorption in the kidney. Dehydration increases ADH, not decreases it, resulting in less urine of higher concentration.来自垂体后叶的 ADH 专门控制肾脏中水的重吸收。脱水使 ADH 增加而非减少，产生量少但浓度高的尿液。
How does the endocrine system differ from the nervous system in how it communicates control signals?内分泌系统与神经系统在传递控制信号的方式上有何不同？
§6 · Q2
Endocrine signals travel faster and have shorter-lasting effects than nerve impulses内分泌信号比神经冲动传递更快，效果持续时间更短
Endocrine signals travel via the blood and have slower onset but longer-lasting effects; nerve impulses travel along neurons and are faster but shorter-lasting内分泌信号通过血液传递，起效较慢但效果持续较长；神经冲动沿神经元传导，更快但持续时间较短
Both systems use identical chemical messengers and work at the same speed两个系统使用相同的化学信使，以相同的速度工作
The nervous system affects internal organs only; the endocrine system affects the brain神经系统仅影响内部器官；内分泌系统影响大脑
The nervous system transmits electrical impulses along neurons (milliseconds); signals are rapid, precise, and short-lived. The endocrine system secretes hormones into the blood (seconds to minutes to reach target); signals are slower, less targeted, and longer-lasting. Both systems work together to maintain homeostasis.神经系统沿神经元传输电冲动（毫秒级）；信号快速、精确且短暂。内分泌系统将激素分泌入血液（到达靶器官需数秒至数分钟）；信号较慢、靶向性较低但持续时间较长。两个系统协同工作以维持稳态。
The key contrast: nervous = fast + precise + short-lived; endocrine = slower + broad + longer-lasting. They complement each other in homeostatic control.关键对比：神经 = 快速 + 精确 + 短暂；内分泌 = 较慢 + 广泛 + 持久。两者在稳态控制中互补。
Section 7 · Integration of control systems第 7 节 · 控制系统的整合

Integration of Nervous and Endocrine Control神经与内分泌控制的整合

Nervous and endocrine systems work together; the hypothalamus is the key bridge (SBI4U E3.1; Biology 30 A2; BC A&P 12).神经与内分泌系统协同工作；下丘脑是关键桥梁（SBI4U E3.1；Biology 30 A2；BC A&P 12）。
  • Comparison: nervous vs endocrine:比较：神经 vs 内分泌：
    Feature特征Nervous system神经系统Endocrine system内分泌系统
    Signal type信号类型Electrical (action potentials)电信号（动作电位）Chemical (hormones in blood)化学信号（血液中的激素）
    Speed速度Milliseconds毫秒级Seconds to minutes数秒至数分钟
    Duration持续时间Brief短暂Minutes to hours数分钟至数小时
    Target specificity靶向特异性Precise (specific muscle or gland)精确（特定肌肉或腺体）Broad (all cells with the receptor)广泛（所有含受体的细胞）
  • The hypothalamus as the master integrator:下丘脑作为主整合器： the hypothalamus receives nerve signals from throughout the body and produces hormones that control the pituitary, making it the key link between the nervous and endocrine systems. It coordinates thermoregulation, osmoregulation, hunger, circadian rhythms, and the stress response.下丘脑接收来自全身的神经信号，并产生控制垂体的激素，使其成为神经系统与内分泌系统之间的关键连接。它协调体温调节、渗透调节、饥饿感、昼夜节律和应激响应。
  • Integrated example — the stress response:整合示例——应激响应： A threat triggers (1) rapid nervous response: the sympathetic nervous system directly signals the adrenal medulla to release adrenaline (epinephrine) within seconds — heart rate and blood glucose increase; (2) slower endocrine response: the hypothalamus releases CRH → pituitary releases ACTH → adrenal cortex releases cortisol (minutes to hours) — sustains elevated blood glucose and suppresses the immune response during prolonged stress. The two pathways reinforce each other and illustrate how the two systems are complementary, not redundant.威胁触发 (1) 快速神经响应：交感神经系统直接信号传递至肾上腺髓质，在数秒内释放肾上腺素——心率和血糖升高；(2) 较慢的内分泌响应：下丘脑释放 CRH → 垂体释放 ACTH → 肾上腺皮质释放皮质醇（数分钟至数小时）——在持续应激期间维持血糖升高并抑制免疫响应。两条路径相互强化，说明两个系统是互补而非冗余的。
  • Disease as homeostatic failure:疾病作为稳态失效： when feedback loops break down, homeostasis fails and disease results. Examples: diabetes mellitus (blood glucose loop fails, §4); hypothyroidism (thyroxine negative feedback impaired → low metabolic rate, fatigue); hypertension (blood pressure regulation fails → sustained high pressure → cardiovascular damage). BC A&P 12 frames disease explicitly as "an imbalance in homeostasis."当反馈回路崩溃时，稳态失效并导致疾病。示例：糖尿病（血糖回路失效，见 §4）；甲状腺功能减退症（甲状腺素负反馈受损 → 代谢率低、疲劳）；高血压（血压调节失效 → 持续高压 → 心血管损伤）。BC A&P 12 明确将疾病定义为"稳态失衡"。
Why integration matters.为何整合至关重要。

No single system can maintain homeostasis alone. The nervous system reacts in milliseconds but cannot sustain effects for hours. The endocrine system sustains effects for hours but cannot react to sudden changes in milliseconds. Real physiological responses — exercise, infection, dehydration — require both systems working in parallel, timed by the hypothalamus as the master controller. SBI4U E3.1 and Biology 30 A2 both require students to "compare the endocrine and nervous control systems and explain how they act together" (Biology 30 A2.5 verbatim).没有任何单一系统能独立维持稳态。神经系统能在毫秒内响应，但无法持续数小时的效果。内分泌系统能维持数小时的效果，但无法在毫秒内响应突变。真实的生理响应——运动、感染、脱水——需要两个系统并行工作，由下丘脑作为主控制器进行协调。SBI4U E3.1 和 Biology 30 A2 均要求学生"比较内分泌和神经控制系统，解释它们如何协同作用"（Biology 30 A2.5 原文）。

During exercise, both the nervous and endocrine systems raise blood glucose. Which statement correctly describes their respective roles?运动期间，神经系统和内分泌系统都能升高血糖。哪项陈述正确描述了它们各自的作用？
§7 · Q1
The nervous system rapidly triggers adrenaline release from the adrenal medulla (seconds); the endocrine system sustains glucose elevation via cortisol from the adrenal cortex (minutes to hours)神经系统快速触发肾上腺髓质释放肾上腺素（数秒）；内分泌系统通过肾上腺皮质的皮质醇持续升高血糖（数分钟至数小时）
The endocrine system responds first (milliseconds); the nervous system sustains the response (hours)内分泌系统先响应（毫秒）；神经系统持续响应（数小时）
Both systems use the same signal type and act at the same speed两个系统使用相同的信号类型，以相同速度运作
Only the endocrine system raises blood glucose; the nervous system only controls movement只有内分泌系统升高血糖；神经系统只控制运动
During acute exercise, sympathetic nerve signals (nervous system) directly stimulate the adrenal medulla to release adrenaline within seconds. Adrenaline triggers immediate glycogenolysis. For sustained exercise, the hypothalamus-pituitary-adrenal cortex axis releases cortisol over minutes to hours, maintaining elevated blood glucose. The two systems are complementary: the nervous system provides the rapid initial burst; the endocrine system sustains the effect.在急性运动期间，交感神经信号（神经系统）在数秒内直接刺激肾上腺髓质释放肾上腺素。肾上腺素触发即时糖原分解。对于持续运动，下丘脑-垂体-肾上腺皮质轴在数分钟至数小时内释放皮质醇，维持血糖升高。两个系统互补：神经系统提供快速的初始爆发；内分泌系统维持效果。
The nervous system is the fast first responder (milliseconds, via adrenaline from the adrenal medulla); the endocrine system sustains the response (cortisol, minutes to hours).神经系统是快速的第一响应者（毫秒级，通过肾上腺髓质的肾上腺素）；内分泌系统维持响应（皮质醇，数分钟至数小时）。
Exam Tactics考试策略

Exam Strategy and Common Pitfalls考试策略与常见陷阱

Feedback loop questions反馈回路题
  • Always name all four components.始终说明全部四个组成部分。 For full marks on a "describe the feedback loop" question: stimulus, receptor, control centre, effector, and the direction of response (opposing or amplifying). Omitting even one component typically costs marks.完整回答"描述反馈回路"问题需说明：刺激、感受器、控制中枢、效应器，以及响应方向（对抗还是放大）。遗漏任何一个组成部分通常会丢分。
  • Distinguish negative from positive feedback by the direction of the response.通过响应方向区分负反馈与正反馈。 Negative: response opposes the original change (corrects it). Positive: response amplifies the original change (drives it further). Do not confuse "negative" with "bad" — most healthy homeostatic loops are negative feedback.负反馈：响应与原始变化相反（纠正它）。正反馈：响应放大原始变化（使其进一步）。不要将"负"等同于"坏"——大多数健康的稳态回路是负反馈。
Hormone and neurotransmitter questions激素与神经递质题
  • State source, target, and effect for every hormone.每种激素均需说明来源、靶器官和效果。 "Insulin lowers blood glucose" alone is incomplete; full answer: "Insulin, released from pancreatic beta cells, stimulates liver and muscle cells to take up glucose and convert it to glycogen, lowering blood glucose." The same applies to glucagon, ADH, aldosterone, and adrenaline.仅写"胰岛素降低血糖"不完整；完整答案："胰岛素由胰腺 β 细胞释放，刺激肝脏和肌肉细胞摄取葡萄糖并将其转化为糖原，从而降低血糖。"胰高血糖素、ADH、醛固酮和肾上腺素同理。
  • Endocrine vs nervous: answer with speed and duration.内分泌 vs 神经：用速度和持续时间作答。 If asked to compare, always state: nervous = fast (ms) + short-lived; endocrine = slower (s to min) + longer-lasting. Then explain why each is suited to its role.若被要求比较，始终陈述：神经 = 快速（毫秒）+ 短暂；内分泌 = 较慢（秒至分钟）+ 持久。然后解释为何各自适合其角色。
ADH and kidney questionsADH 与肾脏题
  • ADH direction: dehydration → more ADH → more concentrated urine (less volume).ADH 方向：脱水 → ADH 增多 → 尿液更浓（量更少）。 Students often reverse this. The logic: dehydrated → blood too concentrated → hypothalamus detects → posterior pituitary releases ADH → collecting duct reabsorbs more water → urine concentrated.学生常将此颠倒。逻辑：脱水 → 血液过浓 → 下丘脑检测 → 垂体后叶释放 ADH → 集合管重吸收更多水 → 尿液浓缩。
  • Diabetes mellitus is a feedback failure, not a water regulation problem.糖尿病是反馈失效，而非水调节问题。 Type 1 = no insulin (beta cells destroyed); Type 2 = insulin produced but cells resist it. Both result in hyperglycemia (high blood glucose) because the normal negative feedback loop is broken.1 型糖尿病 = 无胰岛素（β 细胞被破坏）；2 型糖尿病 = 胰岛素产生但细胞产生抵抗。两者均导致高血糖，因为正常的负反馈回路被破坏。
Active Recall主动复习

Flashcards闪卡

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Define homeostasis.定义稳态（homeostasis）。
The maintenance of a stable internal environment despite changes in external conditions. Achieved via feedback loops.在外部条件变化时维持稳定内环境的过程。通过反馈（反馈）回路实现。
Negative vs positive feedback — key difference?负反馈（negative feedback）vs 正反馈（positive feedback）— 关键区别？
Negative feedback: response opposes the original change (corrects). Positive feedback: response amplifies the original change (e.g. childbirth contractions).负反馈：响应与原始变化相反（纠正）。正反馈：响应放大原始变化（如分娩收缩）。
Four components of a feedback loop?反馈回路的四个组成部分？
Stimulus → Receptor (sensor) → Control centre → Effector → response that corrects or amplifies the stimulus.刺激 → 感受器（传感器）→ 控制中枢 → 效应器 → 纠正或放大刺激的响应。
Thermoregulation: cooling responses when too hot?体温调节（thermoregulation）：体温过高时的降温响应？
Sweating (evaporation removes heat) + vasodilation (more blood near skin surface to radiate heat). Hypothalamus is control centre.出汗（蒸发散热）+ 血管舒张（更多血液流向皮肤表面散热）。下丘脑为控制中枢。
What does ADH do and where is it from?ADH 有什么作用？来自哪里？
ADH (antidiuretic hormone) is released from the posterior pituitary when blood is too concentrated. It increases water reabsorption in the kidney collecting duct → more concentrated urine.ADH（抗利尿激素）在血液过浓时由垂体后叶释放。它增加肾脏集合管中水的重吸收 → 尿液更浓。
Insulin: source, trigger, effect?胰岛素（insulin）：来源、触发条件、效果？
Source: pancreatic beta cells. Trigger: blood glucose above set point. Effect: stimulates cells to take up glucose; liver converts glucose to glycogen. Blood glucose falls.来源：胰腺 β 细胞。触发条件：血糖（血糖）超过设定点。效果：刺激细胞摄取葡萄糖；肝脏将葡萄糖转化为糖原。血糖下降。
Glucagon: source, trigger, effect?胰高血糖素（glucagon）：来源、触发条件、效果？
Source: pancreatic alpha cells. Trigger: blood glucose below set point. Effect: stimulates liver to break down glycogen → glucose released into blood. Blood glucose rises.来源：胰腺 α 细胞。触发条件：血糖低于设定点。效果：刺激肝脏分解糖原 → 葡萄糖释放入血液。血糖升高。
Neuron structure — three main parts?神经元（neuron）结构 — 三个主要部分？
Dendrites (receive signals) → Cell body/soma (integrates) → Axon (conducts action potential away). Synapse connects axon to next cell.树突（接收信号）→ 细胞体（整合）→ 轴突（向外传导动作电位）。突触将轴突连接到下一个细胞。
Reflex arc — correct order?反射弧 — 正确顺序？
Receptor → Sensory neuron → Interneuron (spinal cord) → Motor neuron → Effector. Faster than a brain-mediated response.感受器 → 感觉神经元 → 中间神经元（脊髓）→ 运动神经元 → 效应器。比大脑介导的响应更快。
Hormone definition and how it differs from a neurotransmitter?激素（hormone）定义，与神经递质有何不同？
Hormone: chemical messenger secreted into blood, travels to distant targets, slow onset, long-lasting. Neurotransmitter: crosses synapse (local), milliseconds, brief effect.激素：化学信使，分泌入血液，传至远处靶点，起效慢，持续时间长。神经递质：穿越突触（局部），毫秒级，效果短暂。
Endocrine system: role of the hypothalamus?内分泌（endocrine）系统：下丘脑的作用？
Master integrator: detects changes via nerve signals and blood monitoring, then releases hormones to control the pituitary gland, linking the nervous and endocrine systems.主整合器：通过神经信号和血液监测检测变化，然后释放激素控制垂体，连接神经系统与内分泌系统。
Osmoregulation: what happens when blood is too dilute?渗透调节（osmoregulation）：血液过稀时会发生什么？
Osmolarity falls → hypothalamus reduces ADH release → collecting duct less permeable to water → more dilute urine produced → osmolarity returns to set point.渗透压下降 → 下丘脑减少 ADH 释放 → 集合管对水的通透性降低 → 产生更稀的尿液 → 渗透压回到设定点。
Nervous vs endocrine: speed and duration?神经 vs 内分泌：速度与持续时间？
Nervous: milliseconds, brief. Endocrine: seconds to minutes, long-lasting. Both are controlled by the hypothalamus and work together in homeostasis.神经：毫秒级，短暂。内分泌：秒至分钟，持久。两者均受下丘脑控制，协同维持稳态。
Type 1 vs Type 2 diabetes: core difference?1 型 vs 2 型糖尿病：核心区别？
Type 1: autoimmune destruction of beta cells → no insulin produced → requires insulin injections. Type 2: insulin produced but cells are resistant → managed with diet, exercise, medications.1 型：自身免疫性 β 细胞破坏 → 无胰岛素产生 → 需要胰岛素注射。2 型：胰岛素产生但细胞产生抵抗 → 通过饮食、运动、药物管理。
Mixed Practice综合练习

Practice Quiz综合测验

A person runs a marathon on a hot day. Which combination of responses correctly represents negative feedback maintaining homeostasis?一个人在炎热天气中跑马拉松。哪种响应组合正确代表维持稳态的负反馈？
Q1
Vasoconstriction and shivering血管收缩和颤抖
Increased metabolic rate and increased insulin release代谢率升高和胰岛素分泌增加
Sweating and vasodilation出汗和血管舒张
ADH release and increased urine productionADH 释放和尿液增加
During a hot marathon, core temperature rises above 37 °C (stimulus). The hypothalamus (control centre) activates sweating (evaporative cooling) and vasodilation (radiates heat from skin surface). These responses oppose the temperature rise — negative feedback. Vasoconstriction and shivering would be cold responses; ADH relates to water balance, not temperature.炎热马拉松中，核心体温升至 37 °C 以上（刺激）。下丘脑（控制中枢）激活出汗（蒸发冷却）和血管舒张（从皮肤表面散热）。这些响应与体温升高相反——负反馈。血管收缩和颤抖是对寒冷的响应；ADH 与水平衡相关，而非体温。
When too hot: sweat + vasodilate to lose heat. When too cold: shiver + vasoconstrict to conserve heat. Marathon heat → sweating + vasodilation.体温过高时：出汗 + 血管舒张散热。体温过低时：颤抖 + 血管收缩保热。马拉松高温 → 出汗 + 血管舒张。
A student eats a large sugary meal. Predict the sequence of hormonal events that follows.一名学生吃了一顿含大量糖分的饭。预测随后发生的激素事件序列。
Q2
Glucagon released → glucose taken up by cells → blood glucose falls胰高血糖素释放 → 细胞摄取葡萄糖 → 血糖下降
ADH released → kidney reabsorbs water → blood glucose normalizesADH 释放 → 肾脏重吸收水 → 血糖恢复正常
Insulin released → liver breaks down glycogen to glucose → blood glucose rises further胰岛素释放 → 肝脏分解糖原为葡萄糖 → 血糖进一步升高
Blood glucose rises → pancreatic beta cells release insulin → liver and muscle convert glucose to glycogen → blood glucose falls back to ~5 mmol/L血糖升高 → 胰腺 β 细胞释放胰岛素 → 肝脏和肌肉将葡萄糖转化为糖原 → 血糖回降至约 5 mmol/L
Dietary glucose raises blood glucose (stimulus). Pancreatic beta cells detect this and release insulin. Insulin signals liver and muscle cells to take up glucose and store it as glycogen (glycogenesis). Blood glucose falls toward the set point (~5 mmol/L). Insulin secretion then decreases — negative feedback complete.膳食葡萄糖升高血糖（刺激）。胰腺 β 细胞检测到这一变化并释放胰岛素。胰岛素信号传递至肝脏和肌肉细胞，使其摄取葡萄糖并以糖原形式储存（糖原合成）。血糖回降至设定点（约 5 mmol/L）。随后胰岛素分泌减少——负反馈完成。
High blood glucose triggers insulin (not glucagon) from beta cells (not alpha cells). Insulin promotes glucose storage as glycogen, lowering blood glucose. ADH controls water balance, not glucose.血糖升高触发胰岛素（而非胰高血糖素），来自 β 细胞（而非 α 细胞）。胰岛素促进葡萄糖以糖原形式储存，从而降低血糖。ADH 控制水平衡，而非葡萄糖。
Why does the nervous system respond faster than the endocrine system to a sudden stimulus such as a loud noise?为何神经系统对突然刺激（如巨大噪音）的响应比内分泌系统更快？
Q3
Because hormones travel faster in the blood than action potentials travel along neurons因为激素在血液中的传播速度快于动作电位沿神经元传导的速度
Because nerve impulses (action potentials) travel along neurons directly to the effector in milliseconds, while hormones must be secreted into the blood and carried to their target因为神经冲动（动作电位）在毫秒内直接沿神经元传至效应器，而激素必须分泌入血液并被携带至靶器官
Because the endocrine system does not react to sudden stimuli at all因为内分泌系统根本不对突然刺激做出反应
Because hormones require ATP to be produced, making them slow因为激素需要消耗 ATP 才能产生，使其较慢
Nerve impulses travel along dedicated nerve fibres at up to 120 m/s, reaching the effector in milliseconds. Hormones must first be synthesized or released from a gland, enter the bloodstream, circulate, and then bind target receptors — a process taking seconds to minutes. The nervous system is therefore the fast first-responder; the endocrine system sustains longer-term adjustments.神经冲动沿专用神经纤维以高达 120 m/s 的速度传导，在毫秒内到达效应器。激素必须首先从腺体合成或释放，进入血流，循环流动，然后与靶受体结合——这一过程需要数秒至数分钟。因此神经系统是快速的第一响应者；内分泌系统维持较长期的调整。
Nerve impulses (electrical, along neurons) are faster than hormones (chemical, through blood). Milliseconds vs. seconds-to-minutes.神经冲动（电信号，沿神经元）比激素（化学信号，通过血液）更快。毫秒级 vs. 秒至分钟级。
Blood clotting is triggered when a vessel is damaged: platelets release chemicals that attract more platelets, which release more chemicals, amplifying clot formation until the vessel is sealed. What type of feedback is this?血管损伤时触发凝血：血小板释放化学物质吸引更多血小板，后者释放更多化学物质，放大血块形成直至血管封闭。这是什么类型的反馈？
Q4
Positive feedback, because the response amplifies the original stimulus until a specific endpoint (vessel sealed) stops the loop正反馈，因为响应放大原始刺激，直至特定终点（血管封闭）终止该回路
Negative feedback, because the clot eventually stops bleeding负反馈，因为血块最终止血
Negative feedback, because the chemicals released by platelets are inhibitory负反馈，因为血小板释放的化学物质是抑制性的
Homeostasis, because the body is returning to its normal state稳态，因为机体正在恢复正常状态
Positive feedback amplifies the original change. Here, platelet activation leads to more platelet activation (cascade), driving clotting further and faster. The loop terminates only at a specific endpoint (complete clot). This is not homeostatic — positive feedback deliberately drives the system away from the initial state until a defined outcome is achieved.正反馈放大原始变化。此处，血小板激活导致更多血小板激活（级联反应），使凝血越来越快。该回路只在特定终点（完全血块形成）时终止。这不是稳态——正反馈有意将系统从初始状态推离，直至实现特定结果。
The response (more platelet activation) amplifies, not opposes, the original change (platelet activation) — this is positive feedback, not negative.响应（更多血小板激活）放大而非对抗原始变化（血小板激活）——这是正反馈，而非负反馈。
A patient has a tumour in their thyroid gland that produces excess thyroxine. According to the hypothalamic-pituitary-thyroid negative feedback axis, what would you expect to happen to TSH levels?一名患者甲状腺中有分泌过多甲状腺素的肿瘤。根据下丘脑-垂体-甲状腺负反馈轴，预测 TSH 水平会发生什么变化？
Q5
TSH increases to stimulate even more thyroxine productionTSH 升高以刺激更多甲状腺素产生
TSH stays the same because the thyroid tumour is autonomousTSH 保持不变，因为甲状腺肿瘤是自主的
TSH decreases because high thyroxine suppresses TRH and TSH release (negative feedback)TSH 降低，因为高水平甲状腺素抑制 TRH 和 TSH 的释放（负反馈）
TSH increases because the pituitary detects the tumour directlyTSH 升高，因为垂体直接检测到肿瘤
In a healthy axis: low T4 → hypothalamus releases TRH → pituitary releases TSH → thyroid releases T4 → high T4 suppresses TRH and TSH (negative feedback). If the tumour autonomously produces excess T4, the high T4 strongly suppresses TRH and TSH via negative feedback, so measured TSH levels will be very low (suppressed) even though the thyroid is overactive. This is the basis of thyroid blood-test interpretation.在健康轴中：低 T4 → 下丘脑释放 TRH → 垂体释放 TSH → 甲状腺释放 T4 → 高 T4 抑制 TRH 和 TSH（负反馈）。若肿瘤自主产生过多 T4，高 T4 通过负反馈强烈抑制 TRH 和 TSH，因此即使甲状腺功能亢进，测量到的 TSH 水平也会非常低（被抑制）。这是甲状腺血液检测结果解读的基础。
Negative feedback: high T4 suppresses TSH. The pituitary does not "see" the tumour directly; it sees only the high thyroxine level in the blood, which shuts down TSH secretion.负反馈：高 T4 抑制 TSH。垂体不直接"看到"肿瘤；它只看到血液中高水平的甲状腺素，从而关闭 TSH 分泌。
Self-check自查

Readiness Checklist准备就绪清单

Tick each item when you can do it cold, without notes, on a first attempt.能在无笔记、首次尝试下完成，再勾选每一项。

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Next Steps后续衔接

What This Feeds Into本单元的去向

Homeostasis integrates the nervous and endocrine systems developed in earlier units and provides the physiological framework that Human Anatomy and Physiology (Unit 10) relies on throughout.稳态整合了前几单元发展的神经与内分泌系统，并为人体解剖与生理（第 10 单元）在全程依赖的生理框架提供基础。

Within High School Biology.在 HS Biology 内部。

Human Anatomy and Physiology (Unit 10) applies the organ systems introduced in this guide to a full survey of human systems; the nervous, endocrine, urinary, and circulatory systems all draw on homeostasis as their organizing principle. Cell Structure and Function (Unit 1) is the prerequisite for understanding how receptors and effectors work at the cellular level. Cellular Energetics (Unit 3) underpins why metabolic rate and glucose supply are homeostatic variables. Molecular Genetics (Unit 6) explains why insulin is a protein produced by a specific gene — tying homeostatic regulation back to the molecular level.人体解剖与生理（第 10 单元）将本指南介绍的器官系统应用于人体系统的全面调查；神经、内分泌、泌尿和循环系统均以稳态为组织原则。细胞结构与功能（第 1 单元）是理解感受器和效应器在细胞层面如何工作的先修课。细胞能量学（第 3 单元）解释了为何代谢率和葡萄糖供应是稳态变量。分子遗传学（第 6 单元）解释了为何胰岛素是由特定基因产生的蛋白质——将稳态调控与分子层面联系起来。

Feeds into AP Biology and IB Biology.衔接 AP Biology 与 IB Biology。

AP Biology Unit 8 (Ecology) and Unit 9 (Gene Expression and Regulation) both rely on homeostatic concepts. IB Biology HL C3 (Integration of Body Systems) covers nervous and endocrine integration in the same depth as this guide's §7; IB students should be comfortable with all content here before tackling HL C3 specifics such as hormone cascade pathways and synaptic integration. Neither AP nor IB Biology courses exist yet in this repo; treat this guide as the prerequisite and revisit it when those products ship.AP Biology 第 8 单元（生态学）和第 9 单元（基因表达与调控）均依赖稳态概念。IB Biology HL C3（机体系统整合）以与本指南 §7 相同的深度涵盖神经与内分泌整合；IB 学生在攻克 HL C3 的具体内容（如激素级联通路和突触整合）之前，应熟悉本指南的全部内容。目前这两门课程均未收录于本仓库；将本指南视为先修材料，待相关产品上线后再作衔接。

Feeder note — REMOVED.衔接说明 — 已移除。

No feeder links are shown for this unit; the next-unit links will be added when the adjacent units ship.本单元暂不显示衔接链接；相邻单元上线后将添加后续单元链接。

DINGRUI SCHOLARS

High School Biology · Homeostasis · v1高中生物 · 稳态 · v1