Cyrano Therapeutics

How Does the Sense of Smell Work?

How Does the Sense of Smell Work? Understanding the Olfactory System

The sense of smell is a complex and vital function that enhances our interaction with the world. At Cyrano Therapeutics, we are committed to advancing our understanding of the olfactory system to develop effective treatments for smell loss. Here’s an overview of how this remarkable system works (skip to text):

An overview of the olfactory (smell) system in action:

Understanding the Olfactory System - Loss of Smell

Anatomic Level1

Odor molecules enter the nasal passage and sweep past the olfactory epithelium, where olfactory neurons reside. The odor signal is transmitted through the olfactory nerves into the olfactory bulb and is sent to the brain regions that process smell, including the amygdala, the hippocampus, and the orbitofrontal cortex.

Olfactory neurons - recovering scent

Cellular Level1,2

Olfactory neurons in the olfactory epithelium present cilia into the nasal passage. Odor molecules bind to olfactory receptors on the cilia and trigger an action potential inside the olfactory neuron. This signal is then transmitted to synapses of tufted cells in the glomeruli in the olfactory bulb.

Healthy Olfactory Neurons - Repair Smell

Molecular Level 2-5

Healthy olfactory neurons have numerous olfactory receptors coupled to G proteins.

Upon binding an odor molecule, they activate adenylate cyclase III (ACIII), which generates cyclic adenosine monophosphate (cAMP) from adenosine triphosphate (ATP).

cAMP activates cAMP-gated calcium channels (CNG), leading to calcium influx, which in turn triggers an action potential.

Calcium influx also shuts the cAMP signal down by triggering phosphodiesterase (PDE) activity, leading to cAMP degradation to adenosine monophosphate (AMP).

An Overview of the Olfactory (Smell) System in Action

Anatomical Level

At the anatomical level, odor molecules enter the nasal passage and sweep past the olfactory epithelium, where olfactory neurons reside. These neurons are specialized cells responsible for detecting odor molecules. Once detected, the odor signal is transmitted through the olfactory nerves into the olfactory bulb, a critical brain structure involved in the sense of smell. From the olfactory bulb, the signal is sent to various brain regions that process smell, including the amygdala, hippocampus, and orbitofrontal cortex.

Cellular Level

On the cellular level, the olfactory system’s function begins with the olfactory receptor neurons in the nasal cavity. These neurons have hair-like projections called cilia, which are covered with receptor proteins that bind to odor molecules. This binding initiates a cascade of cellular events that convert the chemical signal of the odor molecule into an electrical signal. This electrical signal travels along the olfactory neurons to the olfactory bulb.

Molecular Level

At the molecular level, the process involves the interaction of odor molecules with specific receptor proteins on the cilia of olfactory neurons. Each receptor protein is designed to bind to particular odor molecules, which explains the wide variety of smells we can detect. When an odor molecule binds to its receptor, it activates a signal transduction pathway that results in the generation of an electrical impulse. This impulse is then transmitted to the brain for further processing and interpretation.

Olfactory System – Loss of Smell

Understanding how the olfactory system works is crucial, especially when addressing smell loss. Damage or dysfunction at any level—anatomical, cellular, or molecular—can result in the loss of smell. This loss can significantly impact an individual’s quality of life, affecting their ability to enjoy food, detect hazards, and experience their environment fully.


At Cyrano Therapeutics, we are dedicated to providing comprehensive insights into the olfactory system and developing innovative treatments for those affected by smell loss. Contact us to learn more about our ongoing research and clinical trials aimed at restoring the sense of smell. Learn more.

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