Of the Sneezing reflex is one of the protective reflexes and corresponds to a "false" external reflex. Sneezing clears the upper airways of nasal secretions and foreign matter to ensure free breathing. Disturbances of the sneezing reflex occur above all after damage to the peripherally and centrally involved nerve tissue, which in addition to the breathing and taste center of the brain, in particular, includes the spinal cord.
What is the sneeze reflex?
Everyone has reflexes. The first instance of any reflex arc is sensory perception. The perceived stimulus is directed via afferent nerves towards the central nervous system, where the reflex arc is connected to certain motor nerves. Through this interconnection, the nerve excitation travels efferent to the body periphery, where it triggers a motor response from the body. This motor response usually corresponds to an uncontrollable muscle contraction. Reflexes are body reactions that the organism involuntarily carries out in response to certain stimuli.
A foreign reflex is the sneezing reflex, the affectors and effectors of which are located in different organs. At the first point of the reflex arc are the mechanoreceptors and chemoreceptors of the nasal mucous membranes. These sensory cells of the skin's senses register touch such as pressure and bind to chemical signals. For the sneezing reflex, a stimulus registered in this way forms the first instance of the reflex arc.
The sneezing reflex is a "fake" reflex, as the stimulus response can be suppressed under certain circumstances. The effectors of the reflex include the respiratory, larynx, mouth and throat muscles.
The main task of the motor reflex response is to clean the upper airways. The sneezing reflex thus corresponds to a protective reflex that frees the nasal mucosa from microorganisms such as bacteria.
Function & task
Researchers recognize the sneeze reflex as an opportunity for a restart that an overwhelmed nose allows itself due to air filtering disorders. The sneezing reflex is triggered by mechano and chemoreceptors in the nasal mucous membrane. These sensory cells register pressure stimuli, for example, which cause the body's own substances such as nasal secretions, foreign substances and microorganisms.
In addition, these sensory cells are located in the pharynx (throat), bronchi and lungs. In addition to contact stimuli, the receptors register chemical substances, fragrances and temperature stimuli. They transport these impulses via primary fibers of the vagus nerve and secondary fibers of the trigeminal nerve to the nucleus tractus solitarii in the diamond pit of the brainstem. In addition, the impulses reach the respiratory center of the formatio reticularis and the spinal cord via the fibers.
The nerve cells that control the executive organs of the sneezing reflex via motor nerves are located in the spinal cord. In addition to the diaphragm and the intercostal muscles, the abdominal muscles are among the executive organs.
The nerve fibers involved in the sneeze reflex are of different quality. When the receptors involved are stimulated, a motor response is triggered involuntarily, starting with a deep reflex inhalation. This is followed by a convulsive exhalation. The soft palate is stretched so that the air mainly escapes through the nose. Sneezing reaches speeds of more than 150 kilometers per hour.
The sneeze reflex cleanses the upper respiratory tract of the body's own secretions and foreign bodies in order to ensure carefree breathing. By cleaning foreign body substances, the sneezing reflex is to be understood in the extended definition as a protective function against infections. In some people, the sneezing reflex can also be triggered by light stimuli and sexual arousal. In this context, light stimuli are referred to as a photopic sneeze reflex.
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Sneezing accompanies many illnesses, for example infections like the flu. The fact that people with the flu have to sneeze more often is due, on the one hand, to the congested nasal secretions and, on the other, to the foreign body bacteria that are in the nose after the infection. The sneeze reflex aims to free the upper airways from both.
Allergies are also associated with a symptomatic sneeze reflex, which in turn is supposed to drive the allergens out of the upper respiratory tract. An increased sneezing reflex thus has pathological value and can point to various diseases such as infections and allergies.
The sneezing reflex is disturbed in people with sinus infections. The inflammation is also known as sinusitis and causes patients to sneeze more often than necessary. Sneezing is related to biochemical signals that influence the activity of the cilia in the sinuses. These cilia on the nose transport the secretion of the mucous membranes including unwanted particles from the sinuses. This evacuation is affected by disorders in patients with sensation.
Not only an increased, but also a decreased or absent sneezing reflex can have pathological value. These phenomena occur mainly after nerve damage. If the conductivity of the individual nerves in the reflex arc is impaired by inflammation, traumatic events or compression, the reflex response is reduced. Inflammation and other types of lesions in the spinal cord or brain can also affect the sneezing reflex.
In this context, lesions in the area of the nucleus solitarius or the formatio reticularis play a role in the brain. Damage in these areas mainly affects the coordination of the sneezing reflex. Lesions in the reticular formation can cause general respiratory impairments and occur primarily in the context of damage to the right hemisphere of the brain. Such in the nucleus solitatius are mainly associated with impairments of the sense of taste. The sneezing reflex can also be impaired by symptoms such as an elevated diaphragm or other diseases of the effector organs.
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