Imagine the smell of a delicious meal coming from the kitchen, the smell of blooming flowers in the yard, or the smell of fresh rain falling on the ground... How much do these smells add to our lives? Some smells bring back old memories, some warn us of danger. So, have you ever wondered how we get this amazing ability, the ability to smell? The main hero behind all this is our olfactory nerve, or ``Olfactory Nerve''. Today, let's talk about this small but very important nerve.
Simply put, what is the olfactory nerve?
The olfactory nerve is the first of 12 special nerves that start in your brain. We call these the cranial nerves. So this is cranial nerve number one (Cranial Nerve I). You might be surprised to hear that this is the shortest sensory nerve in your body. It starts in your brain and ends at the top of your nose, inside.
The main and only function of this nerve is to give you the ability to smell. Anything that has a smell, for example a flower, a food, a perfume bottle, releases tiny, invisible particles into the air. When we breathe, these particles enter the nose. There are cells that are specialized to detect these odor particles. We call them olfactory receptors. These cells send the smell information they have detected directly to the brain via the olfactory nerve. That's when the brain tells us, "Ah... this smell is coming from a bagel" or "This smells like jasmine flowers."
How does the process of smelling happen?
Our olfactory system works in two main ways.
1. Through the Nostrils: When we breathe normally, odorous particles from the environment enter through the nostrils. These particles are detected by the olfactory receptors located at the top of the nose. Like a key, there are receptors that match each odorant particle. It is the way these receptors work together that allows us to detect thousands of different odors.
2. At the back of the throat: When you chew food or take a sip of a drink, odorous particles are released from the food. These particles travel up the throat and reach the olfactory receptors at the back of the nose. That's why sometimes we can taste and smell food at the same time. When you have a cold and your nose is stuffy, food tastes bad because this pathway for smelling is blocked.
Simply put, a large part of our sense of taste depends on our sense of smell. The two are very closely linked.
This special membrane inside the nose
At the top of our nasal cavity is a mucous membrane called the ``Olfactory Mucosa``. This is very important for the sense of smell. It has three main types of cells:
- Olfactory receptor cells: These are the ones that act as sensors to detect specific smells.
- Sustentacular cells: These provide strength and support to other cells, like helpers.
- Basal cells: These are the 'baby' cells that make new receptor cells and supporting cells. Our smell cells die after a while, so these cells are the ones that make new cells to replace them.
What symptoms occur if the function of the olfactory nerve is impaired?
If this olfactory system is affected, various problems can occur. You may have experienced one or more of these.
| Name of the problem (medically) | Simply meaning |
|---|---|
| Anosmia | Complete loss of the sense of smell. A condition in which there is no sense of smell at all. |
| Hyposmia | Loss of sense of smell. Smell is very weak and distant. |
| Parosmia | Distorted sense of smell. For example, your favorite coffee may smell like burnt rubber. Or a floral scent may smell like something rotten. |
| Dysosmia / Phantosmia | Smelling something that isn't really there. You constantly smell an unpleasant odor, like smoke or a chemical, even when there's nothing else around. |
What are the causes of a decreased or lost sense of smell?
There are many reasons that can affect the olfactory nerve. Some are temporary, some are long-term.
- Sinus infection and nasal polyps: Things like colds and sinus infections can cause swelling inside the nose. This prevents odor molecules from reaching the receptors. Nasal polyps can also block the passage in this way.
- Tobacco use: Chemicals released from smoking cigarettes and chewing tobacco damage the delicate cells that sense smell.
- Poor dental hygiene: Bacterial infections in the mouth and dental problems can sometimes affect the sense of smell.
- Severe head injuries: Head injuries, especially concussions, can damage the olfactory nerve. The nerve fibers that pass through the delicate bone between the brain and the nose can be torn.
- COVID-19 virus: A large number of people infected with the coronavirus `(SARS-CoV-2)` have temporarily or possibly permanently lost their sense of smell. This is thought to be due to damage to the olfactory cells and the cells that support them by the virus.
- Certain Medications: Some antibiotics and other medications can cause changes in the sense of smell as a side effect.
- Other diseases: The olfactory nerve can also be affected by diseases related to the nervous system, such as diabetes, Alzheimer's disease, Parkinson's disease, brain tumors, and epilepsy.
- Environmental toxins and chemicals: Exposure to chemicals like pesticides can also damage the olfactory cells.
Are there things we can do to protect ourselves from these problems?
There are some things we can't control, like a brain tumor or Alzheimer's disease, but we can reduce the risk by doing things that are within our control.
- Avoid head injuries: Wear protective equipment like a helmet when playing sports. Avoid risky activities.
- Get the COVID-19 vaccine: Vaccination can reduce severe illness and related complications.
- Avoid smoking: If you are a smoker, quitting is a great help for your sense of smell as well as your overall health.
- Take care of your oral health: Brush and floss your teeth daily.
- Protect yourself from chemicals: If you are working with things like pesticides, wear a mask.
- Get proper treatment for your medical conditions: If you have medical conditions like diabetes, it is important to control them well.
What time should I see a doctor?
A change in your sense of smell can sometimes be an early sign of a serious illness, so it's important to be aware of these things.
If you suddenly lose your sense of smell, or if your sense of smell changes, don't ignore it. It could be a signal from your body.
When to see your doctor:
- If you suddenly lose your sense of smell.
- If the smell of things has changed and feels distorted.
- If you always feel like you smell bad for no reason.
Ignoring these features can also lead to safety issues. Just think,
- What kind of danger could there be if there was no smell of a gas leak?
- What if you didn't smell the smoke of a fire?
- What if you ate expired, spoiled food without smelling it?
Therefore, the sense of smell is not just something we smell, it is also very important for our safety. If you have any such problem, be sure to see your doctor for advice. He or she will be able to find out what is causing this and refer you to the necessary treatment.
Take-Home Message
- The olfactory nerve is a special nerve that comes from the brain that gives us the ability to smell.
- The sense of smell is very important for our sense of taste and safety.
- The sense of smell can be affected by a variety of conditions, from the common cold to COVID-19, diabetes, and head injuries.
- If you experience a sudden change, decrease, or distortion in your sense of smell, do not ignore it and see your doctor immediately.
- Avoiding smoking, protecting your head, and following proper health habits can help protect this nerve.
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