Your olfactory nerve is the first cranial nerve (CN I). This nerve enables your olfactory system and sense of smell. Cranial nerve 1 is the shortest sensory nerve. It starts in your brain and ends in the upper, inside part of your nose.
Your olfactory nerve is the first cranial nerve (CN I). It’s also part of your autonomic nervous system, which regulates body functions. This nerve enables your sense of smell. Cranial nerve 1 is the shortest sensory nerve in your body. It starts in your brain and ends in the upper, inside part of your nose.
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CN I makes it possible to detect scents, odors, aromas and more. Substances that smell give off tiny molecules. Inhaling moves these molecules into your nose. There, special cells (olfactory receptors) detect these molecules. The receptors relay this information to your brain through your olfactory nerve and allow you to perceive smell.
Your olfactory system enables sense of smell in two ways:
Your olfactory mucosa plays a significant role in your ability to smell. This membrane is in the upper part of your nasal cavity and contains different types of cells:
Your olfactory nerve is one of two nerves (visual nerve or cranial nerve 2) that originate directly from your cerebrum. This is the upper part of your brain. Other cranial nerves start in the lower parts of your brain, including your midbrain, pons and medulla oblongata, collectively referred to as your brainstem.
Olfactory nerve fibers travel a short distance to an area in the upper part of your nose (olfactory bulb). Before reaching your olfactory bulb, the nerve fibers pass through your cribriform plate. This spongy, lightweight skull bone separates your nasal area from your brain.
Issues that affect your olfactory system can cause:
Medical conditions and other situations that may affect olfactory nerve function include:
Up to half of the people with COVID-19 experience loss of smell. Researchers are still exploring why. But it’s possible that viral infections, like SARS-CoV-2, the virus that causes COVID-19, damage olfactory receptors. Many people regain their sense of smell. But it can take several months.
It might not be possible to prevent certain conditions from affecting your sense of smell. Complications from neurological disease or brain tumors may be unavoidable.
Preventive measures that are within your control include:
You should contact your healthcare provider if you notice:
It’s important to seek medical attention for these symptoms. They can raise your risk for health and safety issues that include:
A note from Cleveland Clinic
Your olfactory nerve is the first cranial nerve (CN I). This nerve enables your olfactory system and sense of smell. Many conditions can affect cranial nerve 1, including COVID-19, diabetes and Alzheimer’s. It’s important to see your healthcare provider for difficulties with your sense of smell. They can let you know if it’ll come back or return to normal. They may also discuss ways to stay safe and healthy without it.
Last reviewed by a Cleveland Clinic medical professional on 05/21/2022.
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