June 30, 2010
Photo by Exarion, istockphoto
For neuroscientists, asthma is characterized by a hyperactive response in the airways. Lungs contain two important types of receptors, those that slowly adapt (SARs) and those that rapidly adapt (RARs). SARs remain active throughout respiration. RARs, on the other hand, are only active during the initiating moment of inhalation. RARs are believed to be the first line of defense against potential contaminants. It is here, in the NANC nerves, nerves that are responsible for inhibitory and excitatory airway responses, that neurotheorists locate a defect in the system.
Normal Lungs versus Asthmatic Lungs
Whereas someone with a normal lung may experience a mild response with various types of irritants, the asthmatic response is amplified. As Undem and Carr wrote:
"Nonasthmatic subjects may, under appropriate circumstances, experience cough, dyspnea, and chest tightness when their airways are constricted…In some cases of asthma, one might argue that when severe shortness of breath is experienced despite only a mild compromise in lung function, there is an inappropriate hunger for air... Similarly, asthmatics may experience irritating itch sensations in their airways leading to an urge to cough, despite the lack of physical objects in the airway provoking the irritation."
Inappropriate Receptor Signals
Scientists once believed that this overactive response was the result of an inefficient (i.e. weak) immune system, but with further investigation they came to understand that the response was a result of abnormal signals being sent by the receptors. In this state, bronchial muscle contracts, an inappropriate response that results in an asthma attack. It currently isn’t clear what causes this abnormal reaction. The answer to this mystery may lay in future research. However, those in the field of neuropsychology have found an important trend in asthma patients, connected to activation in the nervous system: that symptom progression is highly related to mood and panic.
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