Bronchopulmonary mechanosensors play an important role in the regulation of breathing and airway defense. Regarding the mechanosensory unit, investigators have conventionally adhered to 2 doctrines: one-sensor theory (one afferent fiber connects to a single sensor) and line-labeled theory. Accordingly, lung inflation activates 2 types of mechanosensors: slowly adapting receptors (SARs) and rapidly adapting receptors (RARs) that also respond to lung deflation to produce Hering-Breuer deflation reflex. RARs send signals to a particular brain region to stimulate breathing (labeled as excitatory line) and SARs to a different region to inhibit breathing (inhibitory line). Conventionally, RARs are believed to be mechanosensors, but are also stimulated by a variety of chemicals and mediators. They are activated during different disease conditions and evoke various respiratory responses. In the literature, RARs are the most debatable sensors in the airway. Recent physiological and morphological studies demonstrate that a mechanosensory unit consists of numerous sensors with 4 types, i.e., an afferent fiber connects to multiple homogeneous or heterogeneous sensors (multiple-sensor theory). In addition to SARs and RARs, there are deflation-activated receptors (DARs), which can adapt slowly or rapidly. Each type senses a specific force and generates a unique response. For example, RAR (or SAR) units may respond to deflation if they house DARs responsible for the Hering-Breuer deflation reflex. Multiple-sensor theory requires a conceptual shift because 4 different types of information from numerous sensors carried in an afferent pathway violates conventional theories. Data generated over last eight decades under one-sensor theory require re-interpretation. Mechanosensors and their reflex functions need re-definition. This detailed review of the RARs represents our understanding of RARs under the conventional doctrines, thus it provides a very useful background for interpretation of RAR properties and reflex function against the new proposed multiple-sensor theory.

支气管肺机械传感器在呼吸和气道防御的调节中起重要作用。关于机械感觉单元，研究人员通常坚持 2 条学说：单传感器理论（一根传入纤维连接到单个传感器）和线标记理论。因此，肺膨胀会激活两种类型的机械传感器：缓慢适应受体 (SAR) 和快速适应受体 (RAR)，它们也对肺收缩作出反应以产生 Hering-Breuer 收缩反射。RAR 将信号发送到特定大脑区域以刺激呼吸（标记为兴奋线），而 SAR 发送到不同区域以抑制呼吸（抑制线）。传统上，RAR 被认为是机械传感器，但也会受到各种化学物质和介质的刺激。它们在不同的疾病条件下被激活并引起各种呼吸反应。在文献中，RAR 是气道中最具争议的传感器。最近的生理学和形态学研究表明，一个机械感觉单元由 4 种类型的众多传感器组成，即传入纤维连接到多个同质或异质传感器（多传感器理论）。除了 SAR 和 RAR，还有通货紧缩激活受体 (DAR)，它们可以缓慢或快速地适应。每种类型都能感知特定的力并产生独特的反应。例如，如果 RAR（或 SAR）单元装有负责 Hering-Breuer 通货紧缩反射的 DAR，则它们可能会对通货紧缩做出反应。多传感器理论需要概念上的转变，因为传入通路中携带的来自众多传感器的 4 种不同类型的信息违反了传统理论。过去八年在单一传感器理论下生成的数据需要重新解释。机械传感器及其反射功能需要重新定义。对 RAR 的详细审查代表了我们在传统学说下对 RAR 的理解，因此它为根据新提出的多传感器理论解释 RAR 特性和反射功能提供了非常有用的背景。