Why and How do we sneeze ?Mechanism involved

Chronic exposure to allergens can lead to hyperresponsiveness of the nasal mucosa. As a result, receptors upregulate specific ion channels to increase the sensitivity and potency of their reflex response. Nasal stimuli also affect distant parts of the body. Nerves in the sinus mucosa cause vasodilation; the lacrimal glands can be stimulated by nasal afferent triggers. The sneeze is an airway defense mechanism that removes irritants from the nasal epithelial surface. It is generally benign, but can lead to problems in certain circumstances. The afferent pathway involves histamine-mediated depolarization of H1 receptor-bearing type C trigeminal neurons and a complex coordination of reactions to effect a response.

Sneeze is defined as the involuntary expulsion of air containing irritants from nose.

Causes of sneeze:

• Irritation of nasal mucosa
• Excess fluid in airway

Components of sneeze reflex:

1. Sneeze receptor
2. Afferent nerve
3. Sneeze center
4. Efferent nerve
5. Effector muscle

Mechanism for sneeze:

1. Deep inspiration
2. Opened glottis
3. Expulsion of irritants from both nose and mouth

Pathway for sneeze reflex:

1. Irritation of nasal mucosa
2. Olfactory receptors or V cranial nerve endings
3. Stimulus pass via I and V cranial nerve and reach to Sneeze center in medulla – present in nucleus solitarious and reticular formation
4. Efferent nerves from V, VII, IX, X cranial nerves and intercostal muscles
5. Activation of pharyngeal, tracheal and respiratory muscles

diagram ->>>>>>>>>>>>>>>>>>>>>>

Sneezing Mechanism