查看Ch14 The Autonomic Nervous System的源代码

=== 交感神经输出可以是大量和非特异性的，如战斗或逃跑反应，或对特定靶器官有选择性 ===
<b style=color:#0ae>Sympathetic output can be massive and nonspecific, as in the fight-or-flight response, or selective for specific target organs</b>

In 1915, Walter Cannon N14-6 proposed that the entire sympathetic division is activated together and has a uniform effect on all target organs. In response to fear, exercise, and other types of stress, the sympathetic division produces a massive and coordinated output to all end organs simultaneously, and parasympathetic output ceases. This type of sympathetic output is used to ready the body for life-threatening situations—the so-called fight-or-flight response. Thus, when a person is presented with a fearful or menacing stimulus, the sympathetic division coordinates all body functions to respond appropriately to the stressful situation. This response includes increases in heart rate, cardiac contractility, blood pressure, and ventilation of the lungs; bronchial dilatation; sweating; piloerection; liberation of glucose into the blood; inhibition of insulin secretion; reduction in blood clotting time; mobilization of blood cells by contraction of the spleen; and decreased GI activity. This mass response is a primitive mechanism for survival. In some people, such a response can be triggered spontaneously or with minimal provocation; each individual episode is then called a panic attack.

1915 年，Walter Cannon[N14-6] 提出整个交感神经系统一起被激活，对所有靶器官产生统一的作用。为了应对恐惧、运动和其他类型的压力，交感神经系统同时向所有末梢器官产生大量且协调的输出，副交感神经输出相反作用。这种类型的交感神经输出用于让身体为危及生命的情况做好准备 —— 所谓的战斗或逃跑反应。因此，当一个人受到恐惧或威胁性的刺激时，交感神经部门会协调所有身体功能，以适当地应对压力情况。这种反应包括心率、心脏收缩力、血压和肺通气量的增加、支气管扩张、出汗、竖毛、将葡萄糖释放到血液中、抑制胰岛素分泌、减少血液凝固时间、通过脾脏收缩动员血细胞、和 GI 活性降低。这种大量反应是一种原始的生存机制。在一些人中，这种反应可以自发触发，也可以在最小程度的挑衅下触发；每个单独的发作都称为恐惧袭击。


The fight-or-flight response is an important mechanism for survival, but under normal nonstressful conditions, output of the sympathetic division can also be more discrete and organ specific. In contrast to Cannon’s original proposal, the sympathetic division does not actually produce uniform effects on all visceral targets. Different postganglionic sympathetic neurons have different electrophysiological properties and release other neurotransmitters in addition to norepinephrine. This specific distribution of neuroactive chemicals among neurons is called chemical coding. For example, depolarization of guinea pig postganglionic sympathetic neurons in the lumbar sympathetic chain ganglia causes a brief burst of action potentials in 95% of the neurons and release of norepinephrine together with ATP and neuropeptide Y. These neurons are thought to innervate arteries and to induce vasoconstriction (see Fig. 14-10). In contrast, depolarization of postganglionic sympathetic neurons in the inferior mesenteric ganglion causes sustained firing in 80% of the neurons and release of norepinephrine together with somatostatin. These neurons appear to control gut motility and secretion. Thus, sympathetic neurons have cellular properties that are substantially variable. This variability permits the sympathetic division to produce different effects on targets with different functions.

战斗或逃跑反应是生存的重要机制，但在正常的非应激条件下，交感神经部门的输出也可能更加离散和器官特异性。与 Cannon 最初的提议相反，交感神经划分实际上并没有对所有本能目标产生一致的影响。不同的节后交感神经神经元具有不同的电生理特性，除去甲肾上腺素外 (NA)，还释放其他神经递质。神经活性化学物质在神经元中的这种特定分布称为化学编码。例如，腰交感神经节中豚鼠节后交感神经元的去极化导致 95% 的神经元动作电位短暂爆发，并释放去甲肾上腺素以及 ATP 和神经肽 Y。这些神经元被认为支配动脉并诱导血管收缩（见图 14-10）。相比之下，肠系膜下神经节中节后交感神经元的去极化导致 80% 的神经元持续放电，并释放去甲肾上腺素和生长抑素。这些神经元似乎控制着肠道的运动和分泌。因此，交感神经元具有基本可变的细胞特性。这种可变性允许交感神经分裂对具有不同功能的目标产生不同的影响。

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