📚 Short-Term Effects on the Cardiovascular System | 心血管系统的短期效应
When exercise begins or a sudden stressor appears, the cardiovascular system responds within seconds to deliver more oxygen and glucose to active tissues and to remove carbon dioxide and heat. These short-term effects are largely coordinated by the autonomic nervous system and circulating hormones, and they are reversible once the demand for oxygen returns to resting levels.
当运动开始或突然出现应激时，心血管系统会在数秒内作出反应，为活跃组织输送更多氧气和葡萄糖，并清除二氧化碳和热量。这些短期效应主要由自主神经系统和循环激素协调完成，并且一旦耗氧需求恢复到静息水平，这些变化是可逆的。
1. Defining Short-Term Cardiovascular Responses | 定义短期心血管反应
Short-term responses are the immediate adjustments in heart rate, stroke volume, cardiac output, blood pressure and blood flow distribution that occur within seconds to minutes of increased demand. They do not involve long-term structural changes such as cardiac hypertrophy or increased capillary density.
短期反应是指心率、每搏输出量、心输出量、血压和血流分布在需求增加的数秒到数分钟内发生的即时调整。它们不涉及心肌肥大或毛细血管密度增加等长期结构变化。
These responses are reversible: when exercise stops or the stressor is removed, the cardiovascular variables gradually return to their resting values.
这些反应是可逆的：当运动停止或应激消除后，心血管指标会逐渐恢复到静息值。
2. Autonomic Nervous System Control | 自主神经系统控制
The cardiovascular centre in the medulla oblongata integrates input from higher brain centres, baroreceptors, chemoreceptors and proprioceptors. At the onset of exercise, the parasympathetic (vagal) outflow to the sinoatrial node is reduced, while sympathetic outflow to the heart and blood vessels is increased.
延髓中的心血管中枢整合来自高级脑中枢、压力感受器、化学感受器和本体感受器的信息。运动开始时，迷走神经对窦房结的副交感传出减少，而心脏和血管的交感传出增加。
This shift in autonomic balance raises heart rate within the first few seconds of exercise and increases the force of myocardial contraction.
这种自主神经平衡的转变会在运动开始的几秒内提高心率，并增强心肌收缩力。
3. Heart Rate Response to Exercise | 运动时的心率反应
Resting heart rate is typically around 70 beats per minute (bpm) in an untrained adult. During intense exercise, heart rate can rise to 180-200 bpm, depending on age and fitness.
未经训练的成年人静息心率通常约为每分钟70次（bpm）。在高强度运动中，心率可升至每分钟180-200次，具体取决于年龄和体能。
The initial rapid increase in heart rate is mainly due to withdrawal of vagal tone. Further increases are driven by sympathetic stimulation of the sinoatrial node through noradrenaline release and circulating adrenaline.
心率的初始快速上升主要源于迷走紧张减弱。心率的进一步上升则由去甲肾上腺素释放和循环肾上腺素对窦房结的交感刺激驱动。
4. Stroke Volume and Starling’s Law | 每搏输出量与斯塔林定律
Stroke volume is the volume of blood ejected by each ventricle per beat. At rest it is about 70 mL; during moderate to intense exercise it can increase to 120-140 mL in untrained individuals.
每搏输出量是每个心室每次搏动射出的血液量。静息时约为70 mL；在中等至高强度运动中，未经训练者的每搏输出量可增至120-140 mL。
An important mechanism is Starling’s law of the heart: an increase in venous return stretches the ventricular walls, so the cardiac muscle fibres contract more forcefully and eject more blood.
一个重要机制是心脏的斯塔林定律：静脉回流增加会拉伸心室壁，使心肌纤维更有力地收缩并射出更多血液。
Increased venous return → Increased end-diastolic volume → Stronger contraction → Greater stroke volume
静脉回流增加 → 舒张末期容积增加 → 收缩增强 → 每搏输出量增大
5. Cardiac Output Changes | 心输出量的变化
Cardiac output is the volume of blood pumped by one ventricle per minute. It is calculated as heart rate multiplied by stroke volume.
心输出量是一个心室每分钟泵出的血液量。它等于心率乘以每搏输出量。
Cardiac output = Heart rate × Stroke volume (CO = HR × SV)
心输出量 = 心率 × 每搏输出量 (CO = HR × SV)
At rest, cardiac output is about 5 L/min. During strenuous exercise it can reach 20-40 L/min in trained athletes. This rise delivers much more oxygenated blood to working skeletal muscles.
静息时心输出量约为5 L/min。在高强度运动中，训练有素的运动员可达到20-40 L/min。这一增加为工作的骨骼肌输送了更多含氧血液。
6. Blood Pressure Adjustments | 血压调节
Systolic blood pressure rises during dynamic exercise because the heart pumps more blood per beat into the arteries. A typical systolic value may increase from 120 mmHg at rest to 160-180 mmHg during vigorous exercise.
动态运动期间收缩压升高，因为心脏每次搏动向动脉泵出更多血液。剧烈运动时收缩压可从静息的120 mmHg升至160-180 mmHg。
Diastolic blood pressure usually changes very little or may decrease slightly during aerobic exercise because total peripheral resistance falls as skeletal muscle arterioles dilate.
有氧运动期间舒张压通常变化很小或略有下降，因为骨骼肌小动脉扩张使总外周阻力降低。
The overall effect is a moderate increase in mean arterial pressure, which helps maintain blood flow to vital organs while allowing large increases in flow to active muscles.
总体效果是平均动脉压适度升高，这有助于维持重要器官的血流，同时允许流向活跃肌肉的血流量大幅增加。
7. Redistribution of Blood Flow | 血流量重新分配
At rest, a large proportion of cardiac output goes to the liver, kidneys, gastrointestinal tract and brain. During exercise, blood flow is redirected to skeletal muscles, heart muscle and skin.
静息时，心输出量的很大一部分流向肝脏、肾脏、胃肠道和大脑。运动期间，血流被重新分配到骨骼肌、心肌和皮肤。
Active skeletal muscle arterioles dilate in response to local metabolites such as carbon dioxide, hydrogen ions, potassium ions, adenosine and increased temperature. This is called local vasodilation.
活跃的骨骼肌小动脉在局部代谢物（如二氧化碳、氢离子、钾离子、腺苷和温度升高）作用下扩张。这称为局部血管舒张。
At the same time, sympathetic stimulation causes vasoconstriction in less active regions such as the gut and kidneys, diverting blood to areas with higher oxygen demand.
与此同时，交感刺激引起肠道和肾脏等不太活跃区域的血管收缩，将血液转向需氧量更高的区域。
8. Venous Return and the Muscle Pump | 静脉回流与肌肉泵
Venous return is the flow of blood back to the right atrium. During exercise, three main mechanisms increase venous return: the skeletal muscle pump, the respiratory pump, and venoconstriction.
静脉回流是指血液回流到右心房的过程。运动期间，三个主要机制会增加静脉回流：骨骼肌泵、呼吸泵和静脉收缩。
The skeletal muscle pump works when contracting muscles compress deep veins. One-way valves in the veins ensure blood is pushed towards the heart rather than pooling in the limbs.
骨骼肌泵在肌肉收缩压迫深静脉时发挥作用。静脉中的单向瓣膜确保血液被推向心脏，而不是滞留在四肢。
The respiratory pump is driven by breathing movements: during inspiration, pressure in the thoracic cavity falls and abdominal pressure rises, squeezing blood towards the right atrium.
呼吸泵由呼吸运动驱动：吸气时胸腔内压力下降、腹腔压力升高，将血液挤向右心房。
Venoconstriction, caused by sympathetic stimulation of vein walls, reduces the capacity of venous reservoirs and helps return blood to the heart.
交感神经刺激静脉壁引起的静脉收缩，减少了静脉储血库的容量，有助于血液回流心脏。
9. Hormonal Effects: Adrenaline and Noradrenaline | 激素效应：肾上腺素和去甲肾上腺素
During exercise, the adrenal medulla releases adrenaline and, to a lesser extent, noradrenaline into the blood. These hormones reinforce the effects of sympathetic nerve stimulation.
运动期间，肾上腺髓质向血液中释放肾上腺素以及较少量的去甲肾上腺素。这些激素增强了交感神经刺激的作用。
Adrenaline increases heart rate and contractility by acting on beta-1 receptors in the heart, and it dilates skeletal muscle arterioles via beta-2 receptors. Noradrenaline tends to cause vasoconstriction in most vascular beds through alpha receptors.
肾上腺素通过作用于心脏的β1受体提高心率和收缩力，并通过β2受体扩张骨骼肌小动脉。去甲肾上腺素往往通过α受体引起大多数血管床的血管收缩。
Together, these hormonal effects raise cardiac output and help direct blood to actively working muscles while limiting flow to inactive organs.
这些激素效应共同提高了心输出量，并有助于将血液导向积极工作的肌肉，同时限制流向不活跃器官的血量。
10. Baroreceptor and Chemoreceptor Reflexes | 压力感受器和化学感受器反射
Baroreceptors in the aortic arch and carotid sinus detect changes in blood pressure. During exercise they are reset to allow a higher arterial pressure, preventing an inappropriate fall in heart rate.
主动脉弓和颈动脉窦中的压力感受器检测血压变化。运动期间它们的调定点被重新设定，以允许较高的动脉压，防止心率不适当地下降。
Chemoreceptors in the carotid and aortic bodies detect changes in blood oxygen, carbon dioxide and pH. During heavy exercise, they can stimulate the cardiovascular centre to increase heart rate and blood pressure when metabolic demand is high.
颈动脉体和主动脉体中的化学感受器检测血液氧气、二氧化碳和pH值的变化。在高强度运动中，当代谢需求很高时，它们可以刺激心血管中枢提高心率和血压。
11. Recovery and Return to Resting State | 恢复与回到静息状态
When exercise stops, the short-term cardiovascular effects reverse. Vagal tone increases, sympathetic outflow falls, and heart rate declines rapidly at first, then more slowly as metabolites are cleared.
运动停止后，短期心血管效应发生逆转。迷走紧张增强，交感传出减少，心率首先迅速下降，然后随着代谢物被清除而较缓慢地下降。
Blood pressure returns to normal as cardiac output falls and arterioles in skeletal muscle regain their resting tone. Venous return decreases because the skeletal muscle pump is no longer active.
随着心输出量下降和骨骼肌小动脉恢复静息张力
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