Nasal cycle

Nasal Cycle

The nasal cycle is a physiological process in which the nasal passages undergo alternating partial congestion and decongestion. This cycle is a normal function of the autonomic nervous system and occurs in most humans.

Diagram of the nasal conchae, which play a role in the nasal cycle.

Physiology

The nasal cycle involves the turbinates, also known as the conchae, which are structures within the nasal cavity. These structures swell and shrink in a rhythmic pattern, leading to changes in airflow through the nasal passages. Typically, one side of the nose will be more congested while the other is less so, and this alternates over a period of several hours.

Mechanism

The mechanism behind the nasal cycle is controlled by the autonomic nervous system, specifically the sympathetic nervous system and the parasympathetic nervous system. The cycle is thought to be regulated by the hypothalamus, which influences the dilation and constriction of blood vessels in the nasal mucosa.

Function

The nasal cycle serves several functions, including:

• Humidification and filtration: By alternating airflow between the two nostrils, the nasal cycle helps to maintain optimal conditions for humidifying and filtering the air we breathe.
• Olfaction: The cycle may enhance the sense of smell by allowing one nostril to rest while the other is active.
• Protection: It may protect the nasal mucosa from drying out by ensuring that one side is always less exposed to airflow.

Clinical Significance

While the nasal cycle is a normal physiological process, it can become more pronounced in certain conditions, such as allergic rhinitis or nasal polyps. In some cases, individuals may become aware of their nasal cycle if it leads to significant nasal obstruction.

Related pages

• Nasal cavity
• Turbinates
• Autonomic nervous system
• Allergic rhinitis