Reflexes from airway rapidly adapting receptors

Area of Science:

• Respiratory Physiology
• Neuroscience
• Pulmonology

Background:

• Rapidly adapting receptors (RARs) are sensory receptors located throughout the respiratory tract, from the nose to the bronchi.
• These receptors possess thin myelinated nerve fibers and exhibit irregular discharge patterns, adapting quickly to volume but slowly to chemical stimuli.

Purpose of the Study:

• To elucidate the polymodal nature of RARs, their diverse sensitivities to mechanical and chemical stimuli, and their roles in various respiratory reflexes.
• To differentiate the specific functions and responses of RARs in different regions of the respiratory tract, including the larynx, trachea, and bronchi.

Main Methods:

• The study likely involved physiological recordings and stimulation techniques to investigate RAR responses to various mechanical and chemical stimuli.
• Analysis of reflex outputs such as cough, bronchoconstriction, mucus secretion, and changes in breathing patterns.

Main Results:

• RARs are polymodal, responding to mechanical, chemical, inflammatory, and immunological stimuli.
• RARs in the larynx (irritant receptors) trigger cough, expiration reflex, and laryngeal reflexes.
• RARs in the trachea and bronchi are mechanosensitive, causing cough, bronchoconstriction, and mucus secretion, while those in larger bronchi are also chemosensitive, influencing breathing and laryngeal closure.

Conclusions:

• RARs play a significant role in respiratory reflexes, including cough, mucus secretion, and airway diameter control.
• The diverse sensitivities and reflex responses of RARs highlight their importance in maintaining respiratory homeostasis and responding to irritants.
• The overall reflex response is an additive effect of RARs and other airway receptors, such as C-fibre afferents.