High School Biology — Human Anatomy and Physiology — Solutions

Companion to the Practice Set · Mark-by-mark walkthroughs · AP-Feeder / ON / BC / AB styles练习题配套答案 · 逐分讲解 · AP 衔接 / 安 / 卑 / 阿省考风格

Section A · Worked SolutionsA 部分 · 详细解答

Q1EASY易 🇺🇸 US美 AP-style MCQAP 风格选择题 §1 Levels of Organization生命组织层次 · HS-LS1-2 [3 marks][3 分]

Which of the following correctly lists the levels of biological organization from smallest to largest?下列哪项正确地将生命组织层次从小到大排列？

Answer:答案： (B) Cell → Tissue → Organ → Organ system → Organism细胞 → 组织 → 器官 → 器官系统 → 生物体

Identify the correct sequence找出正确顺序 K1·K1·U1

The hierarchy of biological organization from smallest to largest is: cell (basic unit of life) → tissue (group of similar cells with a shared function) → organ (multiple tissue types working together) → organ system (organs cooperating for a broader function) → organism (all systems integrated). Option (B) matches this sequence exactly.生命组织层次从小到大依次为：细胞（生命基本单位）→ 组织（具有相同功能的同类细胞群）→ 器官（多种组织协同工作）→ 器官系统（多个器官协作完成更广泛功能）→ 生物体（所有系统整合）。选项 (B) 完全符合此顺序。

Why the distractors fail.干扰项分析。

(A): places organ before tissue, reversing the two middle levels.将器官排在组织之前，颠倒了中间两个层次。

(C): places tissue before cell and organism before organ system, breaking both ends of the sequence.将组织排在细胞之前，且生物体排在器官系统之前，两端顺序均错误。

(D): jumps from cell to organ, skipping tissue entirely.从细胞直接跳至器官，完全跳过了组织。

Each level has an emergent property absent from the level below.每个层次都具有下一层次所没有的涌现属性。 A tissue can do things a lone cell cannot (e.g., muscle tissue contracts with coordinated force). An organ integrates tissue types to perform a complex task (e.g., the stomach has epithelial, muscular, and nervous tissue all acting together). Understanding this hierarchy is the entry point for every organ-systems topic in high school biology and AP Biology Unit 2.组织能做单个细胞无法完成的事（例如，肌肉组织能产生协调收缩力）。器官整合多种组织类型以完成复杂任务（例如，胃同时拥有上皮、肌肉和神经组织协同工作）。理解这一层次结构是高中生物学和 AP 生物学第 2 单元所有器官系统专题的切入点。

Q2EASY易 🇺🇸 US美 🇨🇦 ON安 AP-style MCQAP 风格选择题 §2 Digestive System消化系统 · SBI3U E3.2 [3 marks][3 分]

In the human digestive system, where does most chemical digestion and nutrient absorption occur?在人体消化系统中，大多数化学消化和营养物质吸收发生在哪里？

Answer:答案： (C) Small intestine小肠

Identify the site of chemical digestion and absorption确定化学消化与吸收的部位 K1·K1·U1

The small intestine is the primary site of both chemical digestion and nutrient absorption. Pancreatic enzymes (proteases, lipases, amylase) and bile enter the duodenum, completing the breakdown of proteins, fats, and carbohydrates. The enormous surface area provided by villi and microvilli (the brush border) allows efficient absorption of amino acids, fatty acids, monosaccharides, vitamins, and minerals into the bloodstream and lymph.小肠是化学消化和营养物质吸收的主要场所。胰腺酶（蛋白酶、脂肪酶、淀粉酶）和胆汁进入十二指肠，完成蛋白质、脂肪和碳水化合物的分解。绒毛和微绒毛（刷状缘）提供的巨大表面积，使氨基酸、脂肪酸、单糖、维生素和矿物质能够高效吸收进入血液和淋巴。

Why the distractors fail.干扰项分析。

(A) Stomach:胃： digests protein partially (pepsin) and churns food; absorbs almost nothing except some water, alcohol, and aspirin.仅部分消化蛋白质（胃蛋白酶）并研磨食物；几乎不吸收任何物质，除少量水、酒精和阿司匹林。

(B) Large intestine:大肠： reabsorbs water and electrolytes; does not chemically digest macronutrients.重新吸收水分和电解质；不对大分子营养素进行化学消化。

(D) Liver:肝脏： produces bile but is not a site of digestion or absorption.产生胆汁，但不是消化或吸收的场所。

Structure drives function: villi maximize surface area for absorption.结构决定功能：绒毛最大化吸收表面积。 The small intestine is roughly 6-7 m long in adults, but its absorptive surface area is about 250 m2 thanks to circular folds, villi, and microvilli stacked in three layers. This is a classic structure-function relationship tested on AP Biology and all Canadian provincial exams. Remember: the liver makes bile, the gallbladder stores it, the pancreas secretes enzymes, but the small intestine is where the action happens.成人小肠长约 6-7 米，但由于环形皱襞、绒毛和微绒毛三层叠加，其吸收表面积约达 250 平方米。这是 AP 生物学和所有加拿大省级考试必考的经典结构-功能关系。记住：肝脏产生胆汁，胆囊储存胆汁，胰腺分泌酶，但小肠才是消化吸收真正发生的地方。

Q3MEDIUM中 🇨🇦 ON安 🇨🇦 BC卑 ON Provincial-style安大略省考风格 §4 Respiratory System呼吸系统 · SBI3U E3.1 [5 marks][5 分]

Describe the pathway of oxygen from inhaled air to a red blood cell in the lung capillary, naming each structure the oxygen passes through.描述氧气从吸入空气到达肺毛细血管中红细胞的路径，并命名氧气经过的每个结构。

Answer: (a)答案：(a) Nose/mouth → pharynx → larynx → trachea → bronchi → bronchioles → alveolus wall鼻/口 → 咽 → 喉 → 气管 → 支气管 → 细支气管 → 肺泡壁 · (b)(b) Diffusion down a concentration gradient顺浓度梯度扩散

(a) Structural pathway结构路径 K1·K1·K1

Air enters through the nose or mouth, passes through the pharynx (throat), the larynx (voice box), then the trachea (windpipe). The trachea branches into two bronchi (one per lung), which subdivide repeatedly into bronchioles. The finest bronchioles terminate in clusters of alveoli. Oxygen crosses the single-cell-thick alveolus wall and the adjacent capillary wall to enter the blood. Award 1 mark each for any 3 named structures in correct order.空气从鼻或口进入，经过咽（喉咙）、喉（声带所在）、再到气管。气管分叉为左右两条支气管（各通一侧肺），再反复分支成细支气管。最细的细支气管末端形成肺泡簇。氧气穿过仅一个细胞厚的肺泡壁及相邻毛细血管壁进入血液。每正确命名 3 个结构且顺序正确得 1 分。

(b) Mechanism and direction机制与方向 U1·U1

The mechanism is diffusion. Oxygen concentration in the alveolus ($\text{P}_{\text{O}_2} \approx 100\ \text{mmHg}$) is much higher than in the blood arriving from the pulmonary artery ($\text{P}_{\text{O}_2} \approx 40\ \text{mmHg}$). Gases always diffuse from high to low partial pressure, so oxygen moves from the alveolus into the blood. No energy (ATP) is required.机制为扩散。肺泡中氧气浓度（$\text{P}_{\text{O}_2} \approx 100\ \text{mmHg}$）远高于从肺动脉流入的血液（$\text{P}_{\text{O}_2} \approx 40\ \text{mmHg}$）。气体总是从高分压向低分压扩散，因此氧气从肺泡进入血液。不需要能量（ATP）。

Alveoli are optimized for gas exchange by three adaptations.肺泡通过三种适应性结构优化气体交换。 (1) Enormous number (~300 million per lung) provides vast surface area. (2) Walls are one cell thick, minimizing diffusion distance. (3) Rich capillary network maintains a steep concentration gradient by continuously carrying oxygen away. The thin fluid lining and surfactant (reducing surface tension) prevent alveolar collapse. Understanding why diffusion works here (steep gradient, short distance, large area) is the core concept behind all gas-exchange questions on Canadian provincial and AP exams.(1) 数量庞大（每侧肺约 3 亿个），提供巨大表面积。(2) 壁仅一个细胞厚，使扩散距离最短。(3) 丰富的毛细血管网持续将氧气带走，维持陡峭的浓度梯度。薄液膜和表面活性剂（降低表面张力）防止肺泡塌陷。理解扩散在此有效的原因（梯度陡、距离短、面积大），是加拿大省考和 AP 考试所有气体交换题的核心概念。

Q4MEDIUM中 🇨🇦 BC卑 🇨🇦 AB阿 BC Provincial-style卑诗省考风格 §3 Circulatory System循环系统 · SBI3U E3.3 · Bio 20 D GO2 [7 marks][7 分]

A student traces the path of a single red blood cell through the heart and lungs (pulmonary circuit), then through the body (systemic circuit).一名学生追踪一个红细胞穿越心脏和肺（肺循环），再穿越全身（体循环）的路径。

Answer: (a)答案：(a) Right atrium → right ventricle → left atrium → left ventricle右心房 → 右心室 → 左心房 → 左心室 · (b)(b) CO2 released, O2 picked up释放 CO2，携带 O2 · (c)(c) Arteries: thicker muscular walls; carry blood away from heart动脉：壁较厚有肌层；将血液从心脏输出 · (d)(d) Capillaries毛细血管

(a) Sequence of heart chambers心腔顺序 K1·K1

A red blood cell returning from the body carrying $\text{CO}_2$ enters the right atrium, is pumped into the right ventricle, then sent via the pulmonary arteries to the lungs. After gas exchange it returns via the pulmonary veins to the left atrium, drops into the left ventricle, and is pumped out to the body through the aorta. (2 marks for all four chambers in correct order.)携带 $\text{CO}_2$ 从全身返回的红细胞进入右心房，被泵入右心室，再经肺动脉送往肺部。气体交换后经肺静脉返回左心房，流入左心室，经主动脉泵送至全身。（四个腔室全部按正确顺序得 2 分。）

(b) Gas exchange in the lungs肺部气体交换 K1·K1

In the pulmonary capillaries surrounding the alveoli, the red blood cell releases carbon dioxide (high in blood, low in alveolus) and picks up oxygen (high in alveolus, low in blood) by diffusion. Hemoglobin in the red blood cell binds $\text{O}_2$ to form oxyhemoglobin.在围绕肺泡的肺毛细血管中，红细胞通过扩散释放二氧化碳（血液中浓度高，肺泡中浓度低）并携带氧气（肺泡中浓度高，血液中浓度低）。红细胞中的血红蛋白与 $\text{O}_2$ 结合形成氧合血红蛋白。

(c) Arteries vs. veins动脉与静脉的区别 K1·K1

Structural difference: arteries have thicker, more muscular walls to withstand high pressure; veins have thinner walls and contain valves to prevent backflow. Functional difference: arteries carry blood away from the heart (generally oxygenated); veins return blood to the heart (generally deoxygenated). (Accept any 1 structural + 1 functional difference.)结构差异：动脉壁较厚且肌肉层发达，以承受高压；静脉壁较薄，含有瓣膜以防止血液逆流。功能差异：动脉将血液从心脏输出（通常为含氧血）；静脉将血液输回心脏（通常为去氧血）。（任意 1 个结构差异 + 1 个功能差异均可得分。）

(d) Site of gas and nutrient exchange气体与营养物质交换的部位 K1

Capillaries are the site of exchange. Their walls are only one cell thick, allowing efficient diffusion of gases, nutrients, and wastes between the blood and surrounding tissues.毛细血管是交换的场所。其管壁仅一个细胞厚，使血液与周围组织之间的气体、营养物质和代谢废物能够高效扩散。

The heart is a double pump running two circuits in series.心脏是串联运行两套循环的双泵。 The right side powers the pulmonary circuit (heart to lungs and back), while the left side powers the systemic circuit (heart to body and back). A key exam trap: pulmonary arteries carry deoxygenated blood and pulmonary veins carry oxygenated blood, the opposite of what their names suggest. The rule is that arteries always carry blood away from the heart, regardless of oxygen content. Valves (atrioventricular and semilunar) ensure one-way flow through the heart's chambers.右侧驱动肺循环（心脏到肺部再返回），左侧驱动体循环（心脏到全身再返回）。一个关键的考试陷阱：肺动脉携带去氧血，肺静脉携带含氧血，与名称给人的印象相反。规则是：动脉始终将血液从心脏输出，无论含氧量如何。房室瓣和半月瓣确保血液在心腔中单向流动。

Q5MEDIUM中 🇺🇸 US美 🇨🇦 AB阿 AB Diploma-style阿尔伯塔毕业考风格 §6 Immune System免疫系统 · HS-LS1-3 · Bio 20 D GO2 [7 marks][7 分]

The human immune system is described as having three lines of defense against pathogens.人体免疫系统被描述为对抗病原体的三道防线。

Answer: (a)答案：(a) Physical barriers: skin and mucous membranes物理屏障：皮肤与黏膜 · (b)(b) Inflammatory response; phagocytes (neutrophils/macrophages)炎症反应；吞噬细胞（中性粒细胞/巨噬细胞） · (c)(c) Adaptive immunity targets specific antigens; innate does not适应性免疫针对特定抗原；先天免疫则不针对

(a) First line of defense第一道防线 K1·K1

The first line consists of physical and chemical barriers that prevent pathogen entry. Two examples: (1) Skin acts as a physical barrier; its outermost layer (stratum corneum) is tough and difficult for most pathogens to penetrate. (2) Mucous membranes lining the respiratory and digestive tracts trap pathogens in sticky mucus, and cilia sweep them away. Additional examples include tears (lysozyme), saliva, stomach acid, and earwax.第一道防线由防止病原体进入的物理和化学屏障组成。两个例子：(1) 皮肤作为物理屏障；其最外层（角质层）坚韧，大多数病原体难以穿透。(2) 呼吸道和消化道内壁的黏膜将病原体困于黏性黏液中，再由纤毛清除。其他例子包括泪液（溶菌酶）、唾液、胃酸和耳垢。

(b) Second line of defense (non-specific internal)第二道防线（非特异性内部防御） K1·K1·K1

When a pathogen breaches the skin, the second line responds with an inflammatory response: damaged cells release histamine and other signals, causing vasodilation and increased capillary permeability. This brings phagocytes, mainly neutrophils (first to arrive) and macrophages, to the site. These white blood cells engulf and destroy pathogens by phagocytosis. The response is non-specific: it attacks any foreign material in the same way.当病原体突破皮肤时，第二道防线以炎症反应应对：受损细胞释放组胺和其他信号，引起血管扩张和毛细血管通透性增加。这将吞噬细胞（主要是首先到达的中性粒细胞和巨噬细胞）引导至感染部位。这些白细胞通过吞噬作用吞噬并消灭病原体。该反应是非特异性的：以相同方式攻击任何外来物质。

(c) Third line versus second line: specificity第三道防线与第二道防线的区别：特异性 U1·U1

The third line (adaptive immunity) differs because it is antigen-specific. Lymphocytes (B and T cells) recognize unique antigens on a pathogen's surface and mount a tailored response: B cells produce antibodies that bind only to that antigen, and T cells destroy only cells displaying it. The second line is non-specific and attacks all foreign material the same way. Adaptive immunity also produces immunological memory, enabling a faster, stronger response upon re-exposure.第三道防线（适应性免疫）的不同之处在于它具有抗原特异性。淋巴细胞（B 细胞和 T 细胞）识别病原体表面的特异性抗原，并发动针对性反应：B 细胞产生仅与该抗原结合的抗体，T 细胞只消灭显示该抗原的细胞。第二道防线是非特异性的，以相同方式攻击所有外来物质。适应性免疫还产生免疫记忆，使再次接触时能更快、更强地做出反应。

The three lines form a layered, escalating defense system.三道防线构成分层递进的防御体系。 Line 1 is always active (barrier) and requires no immune activation. Line 2 activates within minutes to hours and is pathogen-agnostic (innate immunity). Line 3 takes days to ramp up on first exposure but is exquisitely tailored to the specific pathogen (adaptive immunity). The AB Diploma exam often asks students to categorize a given immune event into one of the three lines, so knowing the distinguishing features of each is essential. Fever (a line-2 response) slows pathogen replication and is driven by pyrogens released by macrophages.第一道防线始终处于激活状态（屏障），无需免疫激活。第二道防线在数分钟至数小时内激活，对病原体无特异性（先天免疫）。第三道防线在首次接触时需要数天才能充分激活，但针对特定病原体精准定制（适应性免疫）。阿尔伯塔毕业考试经常要求学生将某一免疫事件归入三道防线之一，因此了解每道防线的区别特征至关重要。发烧（第二道防线的反应）减缓病原体复制，由巨噬细胞释放的热原驱动。

Section B · Worked SolutionsB 部分 · 详细解答

Q6EASY易 🇺🇸 US美 🇨🇦 ON安 AP-feeder FRQAP 衔接简答题 §5 Nervous System神经系统 · HS-LS1-2 · SBI4U E3.1 [7 marks][7 分]

A student touches a hot stove and immediately pulls their hand away before they feel pain. This is an example of a reflex arc.一名学生碰到热炉子，在感到疼痛之前立刻缩手。这是反射弧的一个例子。

Answer: (a)答案：(a) Receptor → sensory neuron → interneuron (spinal cord) → motor neuron → effector (muscle)感受器 → 传入神经元 → 中间神经元（脊髓）→ 传出神经元 → 效应器（肌肉） · (b)(b) Reflex processed in spinal cord; pain perceived in brain cortex反射在脊髓处理；疼痛感知在大脑皮层 · (c)(c) Somatic: voluntary skeletal muscle control; Autonomic: involuntary organ control躯体神经：自主骨骼肌控制；自主神经：非自主器官控制

(a) Five components of a reflex arc in order反射弧五个组成部分（按顺序） K1·K1·K1

1. Receptor (e.g., thermoreceptors in skin) detects the stimulus (heat). 2. Sensory (afferent) neuron transmits the signal toward the spinal cord. 3. Interneuron (integration center) within the spinal cord gray matter processes the signal and activates a motor response. 4. Motor (efferent) neuron carries the signal away from the spinal cord to the muscle. 5. Effector (skeletal muscle) responds by contracting, pulling the hand away. (1 mark per correctly named and sequenced component, up to 3 marks for any 3 of 5 in correct order.)1. 感受器（如皮肤中的温度感受器）检测刺激（热）。2. 传入（感觉）神经元将信号传向脊髓。3. 脊髓灰质内的中间神经元（整合中枢）处理信号并激活运动反应。4. 传出（运动）神经元将信号从脊髓传至肌肉。5. 效应器（骨骼肌）通过收缩做出反应，将手缩回。（每个正确命名且顺序正确的组件得 1 分，最多 5 个中的任意 3 个正确得 3 分。）

(b) Why the hand pulls away before feeling pain为何在感到疼痛前手已缩回 U1·U1

The reflex is processed in the spinal cord, not the brain. The motor command to withdraw the hand is generated and executed at the spinal level in a fraction of a second. Pain signals, however, must travel all the way to the cerebral cortex (somatosensory area) for conscious perception, which takes longer. The reflex bypasses the brain to enable a faster protective response.反射在脊髓处理，而非大脑。缩手的运动指令在脊髓水平在极短时间内生成并执行。然而，疼痛信号必须一路传至大脑皮层（躯体感觉区）才能被有意识地感知，这需要更长时间。反射绕过大脑，从而实现更快速的保护性反应。

(c) Somatic vs. autonomic nervous system躯体神经系统与自主神经系统 K1·K1

The somatic nervous system controls voluntary movements of skeletal muscle (e.g., raising a hand, walking). The autonomic nervous system controls involuntary functions of smooth muscle, cardiac muscle, and glands (e.g., heart rate, digestion, pupil dilation). The reflex in this question engages the somatic system at the motor output stage, even though the response is involuntary.躯体神经系统控制骨骼肌的自主运动（如举手、走路）。自主神经系统控制平滑肌、心肌和腺体的非自主功能（如心率、消化、瞳孔扩张）。本题中的反射在运动输出阶段涉及躯体神经系统，即使该反应是非自主的。

Reflex arcs save lives by bypassing the slow path through conscious thought.反射弧通过绕过缓慢的意识思维路径来保护生命。 Nerve conduction velocity is about 70-120 m/s for myelinated motor neurons. Even so, a signal from finger to brain and back would take roughly 100-150 ms more than a spinal reflex arc. At the muscular level that delay is significant. All spinal reflex arcs share the same five-component architecture, whether the stimulus is pain, a tendon stretch (knee-jerk), or a sudden loud noise. AP Biology and Ontario SBI4U both expect students to draw and annotate the arc, so being able to sequence the five components with their roles is a non-negotiable skill.有髓运动神经元的神经传导速度约为 70-120 m/s。即便如此，从手指到大脑再返回的信号比脊髓反射弧要多花大约 100-150 毫秒。在肌肉层面这个延迟是显著的。所有脊髓反射弧共享相同的五组件结构，无论刺激是疼痛、肌腱拉伸（膝跳反射）还是突然的响声。AP 生物学和安大略 SBI4U 都要求学生能绘制并标注反射弧，因此能够按顺序写出五个组件及其功能是不可或缺的技能。

Q7MEDIUM中 🇨🇦 ON安 🇨🇦 AB阿 ON Provincial-style安大略省考风格 §2 Digestive System消化系统 · SBI3U E3.2 · Bio 20 D GO1 [8 marks][8 分]

A student eats a sandwich containing bread (starch), chicken (protein), and cheese (fat). Trace what happens to each macromolecule as it travels through the digestive system.一名学生吃了一块含有面包（淀粉）、鸡肉（蛋白质）和奶酪（脂肪）的三明治。追踪每种大分子在消化系统中经历的过程。

Answer: (a)答案：(a) Begins in mouth (salivary amylase); completed in small intestine从口腔开始（唾液淀粉酶）；在小肠完成 · (b)(b) Stomach: pepsin in acidic (HCl) environment denatures and cleaves proteins胃：胃蛋白酶在酸性（HCl）环境中使蛋白质变性并切割 · (c)(c) Bile emulsifies fat; produced in liver, stored in gallbladder胆汁乳化脂肪；由肝脏产生，储存于胆囊

(a) Starch digestion: start and completion sites淀粉消化：起始和完成部位 K1·K1

Starch digestion begins in the mouth. Salivary glands secrete salivary amylase (ptyalin), which hydrolyzes starch into shorter chains (maltose and dextrins). This action stops when food enters the acidic stomach (amylase is denatured). Digestion resumes and is completed in the small intestine, where pancreatic amylase continues the breakdown, and brush-border enzymes (maltase, sucrase, lactase) cleave the final disaccharides into glucose for absorption.淀粉消化从口腔开始。唾液腺分泌唾液淀粉酶（胰淀粉酶的口腔版本），将淀粉水解成较短的链（麦芽糖和糊精）。食物进入酸性胃后此过程停止（淀粉酶被变性）。消化在小肠中恢复并完成，胰淀粉酶继续分解，刷状缘酶（麦芽糖酶、蔗糖酶、乳糖酶）将最终的二糖切割成葡萄糖以供吸收。

(b) Protein digestion in the stomach胃内蛋白质消化 K1·K1·K1

Gastric glands secrete pepsinogen (inactive) and hydrochloric acid (HCl). HCl lowers gastric pH to about 1.5-2, which (1) activates pepsinogen into pepsin, the active protease, and (2) denatures dietary proteins, unfolding them and exposing peptide bonds. Pepsin cleaves proteins into shorter polypeptides. Protein digestion is completed in the small intestine by pancreatic proteases (trypsin, chymotrypsin) and peptidases.胃腺分泌胃蛋白酶原（无活性）和盐酸（HCl）。HCl 将胃内 pH 降至约 1.5-2，这样 (1) 将胃蛋白酶原激活为胃蛋白酶（活性蛋白酶），(2) 使食物蛋白质变性，展开结构并暴露肽键。胃蛋白酶将蛋白质切割成较短的多肽。蛋白质消化在小肠中由胰腺蛋白酶（胰蛋白酶、糜蛋白酶）和肽酶完成。

(c) Role of bile in fat digestion胆汁在脂肪消化中的作用 K1·K1·K1

Bile is not an enzyme; it is an emulsifier. It breaks large fat globules into tiny droplets (emulsification), vastly increasing the surface area available for pancreatic lipase to act on. Without bile, lipase can only work on the fat surface, making digestion far slower. Bile is produced in the liver and stored in the gallbladder, released into the duodenum when fat is detected.胆汁不是酶，而是乳化剂。它将大脂肪球分散成微小液滴（乳化），大大增加了胰脂肪酶的作用表面积。没有胆汁，脂肪酶只能作用于脂肪表面，消化效率大幅降低。胆汁由肝脏产生，储存于胆囊，当检测到脂肪时释放到十二指肠。

Each macromolecule has its own enzyme family and primary site of digestion.每种大分子都有其专属酶系列和主要消化部位。 Carbohydrates (amylases, disaccharidases), proteins (proteases: pepsin, trypsin, chymotrypsin), and lipids (lipase + bile) are processed by distinct enzyme classes. A useful exam shortcut: the stomach is the only organ where protein digestion begins because it provides the acidic environment to activate pepsin. Fats are digested entirely in the small intestine. AB Diploma Biology 20 specifically tests students on identifying which accessory organ produces bile (liver) vs. which stores it (gallbladder), so keep these distinct.碳水化合物（淀粉酶、二糖酶）、蛋白质（蛋白酶：胃蛋白酶、胰蛋白酶、糜蛋白酶）和脂质（脂肪酶 + 胆汁）由不同的酶类处理。一个有用的考试捷径：胃是蛋白质消化开始的唯一器官，因为它提供了激活胃蛋白酶所需的酸性环境。脂肪完全在小肠中消化。阿尔伯塔毕业考试 Biology 20 专门测试学生区分哪个辅助器官产生胆汁（肝脏）和哪个储存胆汁（胆囊），需牢记区分。

Q8MEDIUM中 🇨🇦 BC卑 🇨🇦 AB阿 BC Provincial-style卑诗省考风格 §3 Circulatory System循环系统 · SBI3U E3.3 · Bio 20 D GO2 [8 marks][8 分]

Blood is composed of plasma, red blood cells, white blood cells, and platelets, each with distinct functions in maintaining homeostasis.血液由血浆、红细胞、白细胞和血小板组成，每种成分在维持稳态中各有不同功能。

Answer: (a)答案：(a) Biconcave shape (surface area); no nucleus (more hemoglobin space); hemoglobin binds O2双面凹形（表面积大）；无细胞核（更多空间容纳血红蛋白）；血红蛋白结合 O2 · (b)(b) Platelets aggregate and release clotting factors; fibrin mesh seals the wound血小板聚集并释放凝血因子；纤维蛋白网封闭伤口 · (c)(c) Fatigue (less O2 to tissues); pallor/shortness of breath疲劳（输送到组织的 O2 减少）；面色苍白/气短

(a) Structural adaptations of red blood cells for oxygen transport红细胞携带氧气的结构适应 U1·U1·U1

Red blood cells (erythrocytes) have three key structural adaptations: (1) Biconcave (disc) shape: increases surface area-to-volume ratio compared with a sphere, maximizing the membrane area across which oxygen can diffuse. (2) Absence of a nucleus (and most organelles): frees up interior space entirely for hemoglobin molecules, maximizing oxygen-carrying capacity. (3) Hemoglobin: each red blood cell contains about 280 million hemoglobin molecules, each capable of binding four oxygen molecules; hemoglobin also increases the amount of oxygen dissolved in blood far beyond what plasma alone could carry.红细胞（红血球）有三个关键结构适应：(1) 双面凹盘形：与球形相比，增大表面积与体积之比，最大化氧气可扩散穿过的膜面积。(2) 无细胞核（及大多数细胞器）：将内部空间完全留给血红蛋白分子，最大化携氧能力。(3) 血红蛋白：每个红细胞含约 2.8 亿个血红蛋白分子，每个能结合 4 个氧分子；血红蛋白还使溶于血液的氧气量远超血浆单独所能携带的量。

(b) Role of platelets in blood clotting血小板在凝血中的作用 K1·K1

When a blood vessel is injured, exposed collagen fibers trigger platelets to adhere to the site and aggregate with each other, forming a temporary platelet plug. Platelets also release chemical signals (including thromboplastin/thromboplastins) that activate the coagulation cascade. This cascade converts prothrombin to thrombin, which in turn converts fibrinogen (a soluble plasma protein) to fibrin. Fibrin threads form a mesh that traps red blood cells and hardens into a clot, sealing the vessel wall.当血管受损时，暴露的胶原纤维触发血小板粘附于损伤部位并相互聚集，形成临时血小板栓子。血小板还释放化学信号（包括凝血酶原激酶）激活凝血级联反应。该级联将凝血酶原转化为凝血酶，凝血酶再将纤维蛋白原（一种可溶性血浆蛋白）转化为纤维蛋白。纤维蛋白丝形成网格，困住红细胞并硬化成血块，封闭血管壁。

(c) Predicted symptoms of anemia (low red blood cell count)贫血（低红细胞计数）的预测症状 U1·U1·U1

(1) Fatigue and weakness: fewer red blood cells means less oxygen delivered to muscles and organs per unit time; cells shift to less efficient anaerobic respiration sooner, producing fatigue. (2) Pallor (pale skin): reduced hemoglobin in blood means less red color visible through the skin and in mucous membranes. (3) Shortness of breath: the body compensates by breathing faster to move more oxygen into the blood, but with fewer carriers the effort is still insufficient, leading to breathlessness even at rest or mild exertion. (Accept any 2 of 3 with explanations.)(1) 疲劳和虚弱：红细胞减少意味着单位时间内向肌肉和器官输送的氧气减少；细胞更早转向效率较低的无氧呼吸，产生疲劳。(2) 面色苍白：血液中血红蛋白减少，意味着透过皮肤和黏膜可见的红色减少。(3) 气短：身体通过加快呼吸来补偿，将更多氧气吸入血液，但由于载体减少，努力仍然不足，导致即使在休息或轻微运动时也会气喘。（任意 2 个有解释的症状均可得分。）

Structure-function links in blood components are a classic exam target.血液成分中的结构-功能联系是经典考试重点。 Examiners frequently ask students to connect the biconcave shape of a red blood cell to its oxygen-carrying function. The key principle is that surface area determines the rate of diffusion, so a larger surface area per unit volume means faster loading of oxygen in the lungs and faster unloading in tissues. Anemia questions often appear as clinical scenarios where the student must apply their knowledge of blood composition to predict physiological consequences, a skill tested in AP Biology FRQs and BC Life Sciences 11 exams.考试人员经常要求学生将红细胞的双面凹形与其携氧功能联系起来。关键原理是表面积决定扩散速率，因此单位体积表面积越大，意味着在肺部装载氧气和在组织卸载氧气的速度越快。贫血题目通常以临床情景出现，学生必须运用血液成分知识预测生理后果，这是 AP 生物学简答题和卑诗生命科学 11 考试考查的技能。

Q9HARD难Honors荣誉级 🇨🇦 BC卑 🇨🇦 AB阿 AP-feeder FRQAP 衔接简答题 §7 Endocrine System内分泌系统 · SBI4U E3.1 · Bio 30 A GO2 (above standard floor)（超出标准基准） [7 marks][7 分]

The endocrine system uses hormones to coordinate body functions through negative feedback loops. Consider blood glucose regulation by insulin and glucagon.内分泌系统通过负反馈回路利用激素协调身体功能。以胰岛素和胰高血糖素调节血糖为例。

Answer: (a)答案：(a) Pancreas; beta cells (insulin), alpha cells (glucagon)胰腺；贝塔细胞（胰岛素）、阿尔法细胞（胰高血糖素） · (b)(b) High blood glucose triggers beta cells to release insulin; liver converts glucose to glycogen; blood glucose falls to normal血糖升高刺激贝塔细胞释放胰岛素；肝脏将葡萄糖转化为糖原；血糖恢复正常 · (c)(c) Type 1 diabetes: beta cells destroyed; no insulin produced; high blood glucose persists1 型糖尿病：贝塔细胞被破坏；无胰岛素产生；高血糖持续

(a) Organ and cell types for insulin and glucagon产生胰岛素和胰高血糖素的器官和细胞类型 K1·K1

Both hormones are produced in the pancreas, specifically within clusters of cells called the Islets of Langerhans. Beta cells (B cells) produce insulin, which lowers blood glucose. Alpha cells (A cells) produce glucagon, which raises blood glucose. These two opposing hormones create a push-pull system for tight glucose regulation.两种激素均在胰腺产生，具体在称为朗格汉斯岛（胰岛）的细胞簇中。贝塔细胞（B 细胞）产生胰岛素，降低血糖。阿尔法细胞（A 细胞）产生胰高血糖素，升高血糖。这两种相反的激素构成精密调节血糖的推拉系统。

(b) Negative feedback loop after a meal (high blood glucose)饭后（高血糖）负反馈回路 U1·U1·U1

Stimulus: blood glucose rises above the set point (approximately 5 mmol/L) after a meal. Hormone released: the pancreatic beta cells detect this rise and secrete insulin into the bloodstream. Target organ: the liver (and also muscle and adipose tissue). Physiological effect: insulin stimulates the liver to convert excess glucose into glycogen (glycogenesis) for storage, muscle cells to take up glucose for energy, and adipose cells to convert glucose to fat. As blood glucose falls back toward the set point, less insulin is released, reducing the stimulus. This is the negative feedback: the response (insulin lowering glucose) counteracts the original stimulus (high glucose).刺激：饭后血糖升至设定点（约 5 mmol/L）以上。释放的激素：胰腺贝塔细胞检测到这一升高，将胰岛素分泌到血液中。靶器官：肝脏（以及肌肉和脂肪组织）。生理效应：胰岛素刺激肝脏将多余葡萄糖转化为糖原（糖原合成）储存，肌肉细胞摄取葡萄糖供能，脂肪细胞将葡萄糖转化为脂肪。随着血糖降回设定点，胰岛素分泌减少，刺激减弱。这就是负反馈：反应（胰岛素降低血糖）抵消了原始刺激（高血糖）。

(c) Type 1 diabetes and the broken loop1 型糖尿病与被破坏的回路 U1·U1

In Type 1 diabetes, the immune system mistakenly attacks and destroys the pancreatic beta cells. Without beta cells, no insulin is produced. This breaks the feedback loop at the hormone-secretion step: the stimulus (high blood glucose) is detected, but the response (insulin release) cannot occur. Blood glucose remains chronically elevated (hyperglycemia). Without insulin to signal cells to take up glucose, cells must rely on fat and protein catabolism for energy, leading to serious metabolic consequences.在 1 型糖尿病中，免疫系统错误地攻击并破坏胰腺贝塔细胞。没有贝塔细胞，就不能产生胰岛素。这在激素分泌环节破坏了反馈回路：刺激（高血糖）被检测到，但反应（胰岛素释放）无法发生。血糖持续高于正常水平（高血糖症）。由于没有胰岛素信号让细胞摄取葡萄糖，细胞必须依赖脂肪和蛋白质分解代谢供能，导致严重的代谢后果。

Negative feedback is the universal homeostatic mechanism in physiology.负反馈是生理学中普遍的稳态机制。 Every hormone-mediated homeostatic loop has the same four elements: sensor, control center, effector, and feedback signal. When the output counteracts the input, it is negative feedback (stabilizing). Glucagon works in the opposite direction: when blood glucose falls below the set point, alpha cells release glucagon, which stimulates the liver to break down glycogen (glycogenolysis) and release glucose, raising blood glucose back toward normal. Together, insulin and glucagon create a precise hormonal thermostat, an excellent model system for understanding hormonal regulation broadly. AB Bio 30 and AP Biology both require students to draw and annotate this full loop.每个激素介导的稳态回路都具有相同的四个要素：传感器、控制中心、效应器和反馈信号。当输出抵消输入时，即为负反馈（稳定化）。胰高血糖素的作用方向相反：当血糖低于设定点时，阿尔法细胞释放胰高血糖素，刺激肝脏分解糖原（糖原分解）并释放葡萄糖，将血糖升回正常水平。胰岛素和胰高血糖素共同构成精密的激素恒温器，是广泛理解激素调节的绝佳模型系统。阿省 Bio 30 和 AP 生物学都要求学生能绘制并标注这整个回路。

Section C · Worked SolutionsC 部分 · 详细解答

Q10MEDIUM中 🇺🇸 US美 🇨🇦 AB阿 AB Diploma-style阿尔伯塔毕业考风格 §6 Immune System免疫系统 · HS-LS1-3 · Bio 20 D GO2 [8 marks][8 分]

A student receives a flu vaccine in October. In January, the same student is exposed to the influenza virus but does not develop serious illness. A younger sibling who was not vaccinated contracts the flu with severe symptoms.一名学生在十月接种了流感疫苗。一月份，该学生接触了流感病毒但没有患上严重疾病。未接种疫苗的弟弟/妹妹感染流感后出现严重症状。

Answer: (a)答案：(a) Vaccine antigens triggered primary immune response and production of memory cells; re-exposure triggers rapid secondary response疫苗抗原触发初次免疫反应并产生记忆细胞；再次接触触发快速的次级免疫反应 · (b)(b) Vaccinated: faster, stronger (secondary response); Sibling: slower, weaker (primary response)已接种者：更快更强（次级反应）；弟妹：更慢更弱（初级反应） · (c)(c) Adaptive immunity; involves antigen-specific memory cells适应性免疫；涉及抗原特异性记忆细胞

(a) How the vaccine prepared the immune system (4 marks)疫苗如何使免疫系统做好准备（4 分） K1·K1·U1·U1

The flu vaccine contains antigens from the influenza virus (weakened, inactivated, or subunit proteins) that do not cause disease but are recognized by the immune system. Upon vaccination, the student's immune system mounts a primary immune response: B lymphocytes specific to the influenza antigens are activated and differentiate into (1) plasma cells that produce antibodies targeting those specific antigens, and (2) long-lived memory B cells and memory T cells that persist in the blood. In January, when the student is exposed to the real influenza virus bearing the same antigens, the memory cells recognize the antigens immediately and trigger a rapid, amplified secondary immune response, clearing the virus before serious illness develops.流感疫苗含有来自流感病毒的抗原（减毒、灭活或亚单位蛋白质），不引发疾病但可被免疫系统识别。接种后，学生的免疫系统启动初级免疫反应：特异于流感抗原的 B 淋巴细胞被激活，分化为 (1) 产生针对该特异抗原的浆细胞（抗体），和 (2) 持续存在于血液中的长寿命记忆 B 细胞和记忆 T 细胞。一月份，当学生接触携带相同抗原的真实流感病毒时，记忆细胞立即识别抗原，触发快速、放大的次级免疫反应，在严重疾病发展之前清除病毒。

(b) Comparison of immune responses: vaccinated vs. unvaccinated (3 marks)免疫反应对比：已接种 vs. 未接种（3 分） U1·U1·U1

The vaccinated student's secondary response is dramatically faster (responds within hours rather than days) and stronger (produces far more antibodies with higher specificity) because memory cells are pre-formed and ready. The unvaccinated sibling's primary response takes 7-14 days to generate enough antibodies and effector T cells to control the infection, during which the virus replicates extensively and symptoms are severe. The biological basis is immunological memory: only the adaptive immune system can "remember" a previous encounter with a specific antigen.已接种学生的次级反应明显更快（在数小时内而非数天内响应）且更强（产生更多、特异性更高的抗体），因为记忆细胞已预先形成并准备就绪。未接种弟妹的初级反应需要 7-14 天才能产生足够的抗体和效应 T 细胞来控制感染，期间病毒大量复制，症状严重。生物学基础是免疫记忆：只有适应性免疫系统能够"记住"与特定抗原的先前接触。

(c) Innate or adaptive immunity?先天免疫还是适应性免疫？ K1

This is an example of adaptive (acquired) immunity, because the protection is based on antigen-specific memory cells (B and T memory cells) produced during the primary immune response to the vaccine, which are specific to influenza antigens and enable the faster secondary response.这是适应性（获得性）免疫的例子，因为保护作用基于在对疫苗的初级免疫反应期间产生的抗原特异性记忆细胞（B 和 T 记忆细胞），这些细胞特异于流感抗原，使次级反应更快。

Vaccines exploit immunological memory to prevent disease before exposure.疫苗利用免疫记忆在接触病原体前预防疾病。 The vaccine essentially "tricks" the immune system into mounting a primary response against harmless antigens, so that when the real pathogen arrives, the immune system is already primed. This is why the secondary response (to the actual flu virus in January) is so much faster than the sibling's primary response. The key distinction the exam tests: the speed advantage of the secondary response comes entirely from pre-existing memory cells, not from a stronger innate response. Herd immunity arises when enough of the population has adaptive memory that transmission chains break, protecting even unvaccinated individuals indirectly.疫苗本质上"欺骗"免疫系统对无害抗原产生初级反应，这样当真正病原体到来时，免疫系统已经预先准备好了。这就是为什么次级反应（一月份对真实流感病毒）比弟妹的初级反应快得多。考试测试的关键区别：次级反应的速度优势完全来自预先存在的记忆细胞，而非更强的先天反应。当足够多的人口拥有适应性记忆使传播链断裂时，就产生群体免疫，从而间接保护未接种的个体。

Q11MEDIUM中 🇨🇦 ON安 🇨🇦 AB阿 ON Provincial-style安大略省考风格 §5 Nervous System神经系统 · SBI4U E3.1 · Bio 30 A GO1 [8 marks][8 分]

A neuron at rest has a resting membrane potential of approximately $-70\ \text{mV}$. When stimulated, an electrical signal (nerve impulse) travels along the neuron.一个处于静息状态的神经元，其静息膜电位约为 $-70\ \text{mV}$。受刺激时，电信号（神经冲动）沿神经元传导。

Answer: (a)答案：(a) High Na+ outside, high K+ inside; Na+/K+ ATPase pump maintains gradientNa+ 高浓度在外，K+ 高浓度在内；Na+/K+ ATP 酶泵维持梯度 · (b)(b) Na+ channels open first (depolarization); K+ channels open second (repolarization)Na+ 通道先开放（去极化）；K+ 通道后开放（复极化） · (c)(c) Myelin sheath insulates axon; saltatory conduction between nodes speeds impulse髓鞘绝缘轴突；郎飞节间的跳跃传导加快冲动速度

(a) Origin of the resting membrane potential ($-70\ \text{mV}$)静息膜电位（$-70\ \text{mV}$）的成因 U1·U1·U1

The resting membrane potential is created by an unequal distribution of ions across the membrane, maintained by the sodium-potassium ATPase pump (Na+/K+ pump). At rest: (1) Sodium ions ($\text{Na}^+$) are in high concentration outside the cell and low inside; the membrane is relatively impermeable to $\text{Na}^+$ at rest. (2) Potassium ions ($\text{K}^+$) are in high concentration inside the cell; some $\text{K}^+$ leaks out through potassium leak channels, making the inside more negative. The Na+/K+ pump actively transports 3 $\text{Na}^+$ out and 2 $\text{K}^+$ in per cycle, maintaining the gradient at the cost of ATP. The net result is a negative interior relative to the exterior, giving $-70\ \text{mV}$.静息膜电位由膜两侧离子的不均等分布产生，由钠钾 ATP 酶泵（Na+/K+ 泵）维持。静息时：(1) 钠离子（$\text{Na}^+$）在细胞外浓度高、细胞内浓度低；静息时膜对 $\text{Na}^+$ 相对不透。(2) 钾离子（$\text{K}^+$）在细胞内浓度高；部分 $\text{K}^+$ 通过钾泄漏通道渗出，使细胞内部更负。Na+/K+ 泵每循环主动转运 3 个 $\text{Na}^+$ 出和 2 个 $\text{K}^+$ 入，消耗 ATP 维持梯度。最终结果是内部相对外部为负，给出 $-70\ \text{mV}$。

(b) Ion movements during an action potential动作电位期间的离子运动 U1·U1·U1

Depolarization (Na+ channels open first): when a threshold stimulus is reached, voltage-gated Na+ channels open rapidly. $\text{Na}^+$ rushes into the cell along its concentration and electrical gradient, making the interior more positive (membrane potential rises from $-70$ mV toward $+30$ to $+40$ mV). Repolarization (K+ channels open second): voltage-gated Na+ channels inactivate. Voltage-gated K+ channels then open (slightly delayed), and $\text{K}^+$ flows out of the cell, restoring the negative interior. A brief hyperpolarization may occur before the Na+/K+ pump restores the original resting concentrations.去极化（Na+ 通道先开放）：当刺激达到阈值时，电压门控 Na+ 通道迅速开放。$\text{Na}^+$ 沿浓度梯度和电梯度涌入细胞，使内部变得更正（膜电位从 $-70$ mV 升至 $+30$ 到 $+40$ mV）。复极化（K+ 通道后开放）：电压门控 Na+ 通道失活。电压门控 K+ 通道随后开放（略有延迟），$\text{K}^+$ 流出细胞，恢复负的内部电位。在 Na+/K+ 泵恢复原始静息浓度之前，可能发生短暂的超极化。

(c) Myelin sheath and saltatory conduction髓鞘与跳跃传导 K1·U1

The myelin sheath is a fatty layer produced by Schwann cells (peripheral nervous system) or oligodendrocytes (central nervous system) wrapped around the axon. It acts as electrical insulation, preventing ion flow through the axon membrane at myelinated sections. Action potentials can only occur at the nodes of Ranvier (gaps in the myelin). The impulse therefore "jumps" from node to node, a process called saltatory conduction (from Latin saltare, to jump). This is much faster than continuous conduction along an unmyelinated axon because the signal skips large sections of the axon rather than propagating continuously.髓鞘是施万细胞（外周神经系统）或少突胶质细胞（中枢神经系统）缠绕在轴突周围形成的脂肪层。它起到电绝缘作用，防止离子在髓鞘化部分通过轴突膜流动。动作电位只能在郎飞节（髓鞘间隙）处发生。冲动因此从节点"跳"到节点，这一过程称为跳跃传导（来自拉丁语 saltare，跳跃）。这比沿无髓鞘轴突的连续传导快得多，因为信号跳过轴突的大段而非连续传播。

The action potential is all-or-nothing: either threshold is met and the full spike fires, or nothing happens.动作电位遵循全或无原则：要么达到阈值并产生完整的电位峰，要么什么都不发生。 Once threshold ($\approx -55$ mV for most neurons) is crossed, the Na+ channels open in a positive feedback loop: Na+ influx makes the inside more positive, which opens more Na+ channels, which drives more Na+ in, until all channels are open. The magnitude of the action potential is fixed regardless of how strong the stimulus was. Stimulus strength is instead encoded by the frequency of action potentials (rate coding). Myelination by Schwann cells is disrupted in multiple sclerosis, slowing or blocking nerve conduction and explaining the motor and sensory symptoms of that disease.一旦超过阈值（大多数神经元约 $-55$ mV），Na+ 通道以正反馈回路开放：Na+ 内流使内部更正，开放更多 Na+ 通道，驱使更多 Na+ 内流，直到所有通道开放。动作电位的幅度固定，与刺激强度无关。刺激强度改为通过动作电位的频率编码（频率编码）。多发性硬化症中施万细胞的髓鞘化被破坏，减慢或阻断神经传导，解释了该疾病的运动和感觉症状。

Q12HARD难 🇨🇦 BC卑 🇨🇦 AB阿 AP-feeder FRQAP 衔接简答题 §1 + §4 + §5 Homeostasis (multi-system integration)稳态（多系统整合） · SBI3U E3.1 · SBI4U E3.1 [9 marks][9 分]

During intense exercise, a student's muscles demand far more oxygen and glucose than at rest, and produce large amounts of carbon dioxide and heat. Multiple organ systems coordinate to maintain homeostasis.在剧烈运动中，学生肌肉对氧气和葡萄糖的需求远高于静息状态，并产生大量二氧化碳和热量。多个器官系统协同维持稳态。

Answer: (a)答案：(a) High CO2 detected by chemoreceptors; negative feedback triggers faster/deeper breathing to expel CO2化学感受器检测到高 CO2；负反馈触发加快/加深呼吸以排出 CO2 · (b)(b) Heart rate and breathing rate increase; vasodilation in active muscles; vasoconstriction elsewhere心率和呼吸频率加快；活跃肌肉血管扩张；其他部位血管收缩 · (c)(c) Sympathetic; dilated pupils, increased sweating, bronchodilation, reduced digestion交感神经系统；瞳孔扩大、出汗增加、支气管扩张、消化减弱

(a) Respiratory response to elevated blood CO2呼吸系统对血液 CO2 升高的响应 U1·U1·U1

During exercise, muscles produce more $\text{CO}_2$ through cellular respiration. $\text{CO}_2$ dissolves in the blood plasma to form carbonic acid ($\text{H}_2\text{CO}_3$), which dissociates into $\text{H}^+$ and $\text{HCO}_3^-$, lowering blood pH. Central chemoreceptors in the medulla oblongata (and peripheral chemoreceptors in the aorta and carotid bodies) detect the rise in $\text{CO}_2$ and fall in pH. They send signals to the respiratory center in the medulla, which increases the rate and depth of breathing. This is a negative feedback mechanism: the increased breathing expels more $\text{CO}_2$ from the lungs, reducing blood $\text{CO}_2$ and returning pH toward normal.运动时，肌肉通过细胞呼吸产生更多 $\text{CO}_2$。$\text{CO}_2$ 溶于血浆形成碳酸（$\text{H}_2\text{CO}_3$），解离为 $\text{H}^+$ 和 $\text{HCO}_3^-$，降低血液 pH 值。延髓中的中枢化学感受器（以及主动脉和颈动脉体中的外周化学感受器）检测到 $\text{CO}_2$ 升高和 pH 降低。它们向延髓中的呼吸中枢发送信号，后者增加呼吸频率和深度。这是负反馈机制：加深呼吸将更多 $\text{CO}_2$ 从肺中排出，降低血液 $\text{CO}_2$，使 pH 恢复正常。

(b) Circulatory and respiratory systems working together循环系统和呼吸系统的协同作用 U1·U1·U1

The circulatory and respiratory systems cooperate through three main adjustments: (1) Increased heart rate: the sympathetic nervous system stimulates the heart to beat faster and with greater force (increased cardiac output), delivering oxygenated blood to muscles more rapidly. (2) Increased breathing rate and depth: more oxygen enters the blood at the alveoli and more $\text{CO}_2$ is expelled per minute. (3) Redistribution of blood flow: blood vessels in active skeletal muscles dilate (vasodilation), while vessels supplying less active tissues (e.g., digestive organs, skin in cool conditions) constrict (vasoconstriction). This preferentially directs blood to where oxygen demand is highest.循环系统和呼吸系统通过三种主要调整协同工作：(1) 心率加快：交感神经系统刺激心脏更快、更有力地跳动（心输出量增加），更迅速地将含氧血液输送到肌肉。(2) 呼吸频率和深度增加：每分钟有更多氧气在肺泡进入血液，更多 $\text{CO}_2$ 被排出。(3) 血流重新分配：活跃骨骼肌中的血管扩张（血管扩张），而供应不太活跃组织（如消化器官、凉爽条件下的皮肤）的血管收缩（血管收缩）。这将血液优先导向氧气需求最高的部位。

(c) Branch of autonomic nervous system activated; three additional effects激活的自主神经系统分支；三种额外的生理变化 K1·U1·U1

The sympathetic nervous system (the "fight-or-flight" division) is activated during exercise. Beyond increased heart rate, three specific physiological changes include: (1) Bronchodilation: airways in the lungs widen, reducing resistance and allowing greater airflow per breath. (2) Increased sweating: sweat glands become more active to dissipate the excess body heat generated by working muscles (thermoregulation). (3) Pupil dilation (mydriasis): eyes open wider to improve vision during exertion. Additional acceptable responses: reduced digestive activity (blood diverted away), increased blood glucose (epinephrine/adrenaline stimulates glycogen breakdown), or suppressed immune and reproductive function.运动时交感神经系统（"战斗或逃跑"分支）被激活。心率加快之外，三种具体的生理变化包括：(1) 支气管扩张：肺中气道变宽，减少阻力，每次呼吸通气量更大。(2) 出汗增加：汗腺更加活跃，散发运动肌肉产生的多余体热（体温调节）。(3) 瞳孔扩大（散瞳）：眼睛开得更大，改善运动时的视觉。其他可接受的答案：消化活动减弱（血液转离消化系统）、血糖升高（肾上腺素刺激糖原分解）、或免疫和生殖功能受抑制。

Exercise integrates at least five organ systems simultaneously, making it the ultimate multi-system homeostasis scenario.运动同时整合至少五个器官系统，使其成为终极的多系统稳态情景。 This question tests the highest-order skill in physiology: integrating knowledge across organ systems rather than recalling isolated facts. The key principle is that all adjustments during exercise are homeostatic: each response counteracts a specific perturbation (CO2 builds up, heart expels it faster; temperature rises, sweat glands cool the body; O2 demand rises, breathing and heart rate increase to supply it). Provincial and AP examiners reward students who explicitly link stimulus to response to homeostatic outcome. Practicing this "perturbation-to-response" reasoning for each organ system is the fastest path to top marks on multi-system questions.这道题测试生理学中最高层次的技能：跨器官系统整合知识，而非回忆孤立事实。关键原理是运动中所有调整都是稳态性的：每个反应都抵消特定的扰动（CO2 积聚，心脏更快排出；体温升高，汗腺冷却身体；O2 需求升高，呼吸和心率增加以供给）。省考和 AP 考试阅卷人奖励那些明确将刺激与反应和稳态结果相联系的学生。对每个器官系统练习这种"扰动-反应"推理，是在多系统题中获得高分的最快途径。