查看Ch14 The Autonomic Nervous System的源代码

=== 内脏控制系统也有一个重要的传入肢体 ===
<b style=color:#0ae>The visceral control system also has an important afferent limb</b>

All internal organs are densely innervated by visceral afferents. Some of these receptors monitor nociceptive (painful) input. Others are sensitive to a variety of mechanical and chemical (physiological) stimuli, including stretch of the heart, blood vessels, and hollow viscera, as well as PCO2, PO2, pH, blood glucose, and temperature of the skin and internal organs. Many visceral nociceptive fibers travel in sympathetic nerves (blue projections in Fig. 14-2). Most axons from physiological receptors travel with parasympathetic fibers. As is the case with somatic afferents (see p. 271), the cell bodies of visceral afferent fibers are located within the dorsal root ganglia or cranial nerve ganglia (e.g., nodose and petrosal ganglia). Ninety percent of these visceral afferents are unmyelinated.

所有内脏器官都由内脏传入神经密集支配。其中一些受体监控伤害性（痛苦）输入。其他对各种机械和化学（生理）刺激敏感，包括心脏伸展、血管和空腔内脏，以及 PCO2、PO2、pH、血糖以及皮肤和内脏器官的温度。许多内脏伤害性纤维在交感神经中行进（图 14-2 中的蓝色投影）。来自生理受体的大多数轴突与副交感神经纤维一起移动。与体细胞传入神经一样（见第 271 页），内脏传入纤维的细胞体位于背根神经节或颅神经节（例如，结节和岩神经节）内。这些内脏传入神经中有 90% 是无髓的。


The largest concentration of visceral afferent axons can be found in the vagus nerve, which carries non-nociceptive afferent input to the CNS from all viscera of the thorax and abdomen. Most fibers in the vagus nerve are afferents, even though all parasympathetic preganglionic output (i.e., efferents) to the abdominal and thoracic viscera also travels in the vagus nerve. Vagal afferents, whose cell bodies are located in the nodose ganglion, carry information about the distention of hollow organs (e.g., blood vessels, cardiac chambers, stomach, bronchioles), blood gases (e.g., PO2, PCO2, pH from the aortic bodies), and body chemistry (e.g., glucose concentration) to the medulla.

内脏传入轴突的最大集中体可以在迷走神经中找到，迷走神经将非伤害性传入输入从胸部和腹部的所有内脏传递到 CNS。迷走神经中的大多数纤维是传入神经，即使所有副交感神经节前输出（即传出神经）到腹部和胸部内脏也都在迷走神经中移动。迷走神经传入神经的细胞体位于结节神经节中，将有关空心器官（例如血管、心腔、胃、细支气管）、血气（例如主动脉体的 PO2、PCO2、pH 值）和身体化学成分（例如葡萄糖浓度）的膨胀信息带到髓质。


Internal organs also have nociceptive receptors that are sensitive to excessive stretch, noxious chemical irritants, and very large decreases in pH. In the CNS, this visceral pain input is mapped (see pp. 400–401) viscerotopically at the level of the spinal cord because most visceral nociceptive fibers travel with the sympathetic fibers and enter the spinal cord at a specific segmental level along with a spinal nerve (see Fig. 14-2). This viscerotopic mapping is also present in the brainstem but not at the level of the cerebral cortex. Thus, awareness of visceral pain is not usually localized to a specific organ but is instead “referred” to the dermatome (see p. 273) that is innervated by the same spinal nerve. This referred pain results from lack of precision in the central organization of visceral pain pathways. Thus, you know that the pain is associated with a particular spinal nerve, but you do not know where the pain is coming from (i.e., from the skin or a visceral organ). For example, nociceptive input from the left ventricle of the heart is referred to the left T1 to T5 dermatomes and leads to discomfort in the left arm and left side of the chest, whereas nociceptive input from the diaphragm is referred to the C3 to C5 dermatomes and is interpreted as pain in the shoulder. This visceral pain is often felt as a vague burning or pressure sensation.

内部器官也有伤害性受体，对过度拉伸、有害化学刺激物和 pH 值大幅下降敏感。在 CNS 中，这种内脏疼痛输入在脊髓水平的内脏位上映射（见第 400-401 页），因为大多数内脏伤害性纤维与交感神经一起移动，并与脊神经一起在特定节段水平进入脊髓（见图 14-2）。这种内脏映射也存在于脑干中，但不存在于大脑皮层的水平。因此，对内脏疼痛的意识通常不局限于特定器官，而是“指代”由同一脊神经支配的皮节（见第 273 页）。这种牵涉痛是由于内脏疼痛通路的中心组织缺乏精确性造成的。因此，您知道疼痛与特定的脊神经有关，但您不知道疼痛来自哪里（即来自皮肤或内脏器官）。例如，来自心脏左心室的伤害性输入被称为左 T1 到 T5 皮节，并导致左臂和胸部左侧的不适，而来自横膈膜的伤害性输入被称为 C3 到 C5 皮节，并被解释为肩部疼痛。这种内脏疼痛通常表现为隐约的灼热感或压迫感。

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