Olfactory System

Olfactory System Definition

You've likely studied a bit about the five senses at school. Our basic senses are seeing, hearing, smelling, tasting, and touch. Our sense of smell is also called olfaction.

When we think of smell, we immediately think of our noses, of course. However, there is an entire system of parts and processes that make up our experience of smell. This system is called the olfactory system.

Woman smelling a flower, pixabay

Olfactory System: Parts and Functions

The four major parts of the olfactory system are the nasal cavity, olfactory receptors, olfactory bulb, and the olfactory nerve. Here are each of these parts and the things that they do:

• Nasal cavity is just a fancy word for nostril. We have two nostrils, so we have two nasal cavities.
• Olfactory receptors are cells that absorb and react to odor molecules.
• The olfactory bulb looks like a tiny plant bulb and is located at the tip of the brain's frontal lobe. It receives signals and sends them to higher areas of the brain.
• The olfactory nerve is made up of sensory nerve fibers. It is connected to the olfactory bulb, where it receives information and carries it to other areas of the brain.

Now let's take a look at how smelling actually occurs. Our nasal cavities, or nostrils, allow molecules of scent or odor to enter our nose. At the top of each nasal cavity are our olfactory receptor cells, protected within a mucus membrane. Odor molecules dissolve within this membrane. Our olfactory receptors have tiny, hair-like, extensions on the ends of them.

These extensions have chemical receptors on them that interact with the odor molecules that dissolve within the mucus membrane. Odor molecules will bind with the chemical receptors and create a chemical change within the receptor cells. The chemical change sends a signal to the olfactory bulb. All of this information is then transmitted to higher areas of the brain by way of the olfactory nerve.

This is why scent, or olfaction, is called a chemical sense. A chemical change or exchange takes place along the chemical receptors in our olfactory system that allow us to experience smell.

Various fresh spices, pixabay

Olfactory System Receptors

Whether it's a flower, a plate of nachos, fresh mown grass, or your best friend, we smell everything around us. Everything around us gives off molecules of odor, fragrance, or smell. In a way, we really do breathe in everything around us!

These tiny elements of odor enter our noses and travel through the olfactory system to create a smell experience. Sometimes it's a good experience, like with the nachos or fresh mown grass. Other times, it's not the best experience! These experiences are made possible by our olfactory system receptors.

Olfactory System and Memory

But wait! What about the memory of riding in the car with our childhood friend and their mom? Why is our sense of smell more likely to conjure up such a random memory better than sight, or seeing the same type of car we used to ride in?

Our sense of smell is actually considered a primitive sense. It's ancient! Before our brains even evolved into what they are today, ancient man relied on his sense of smell to find food and avoid spoiled or poisonous things in nature. Before human beings had sophisticated reason skills or methods of communication, we were already relying heavily on our sense of smell to keep us safe.

Our more primitive ancestors relied on their sense of smell to find a mate and pass on their genes by smelling each other's pheromones.

One reason researchers believe smell and memory are so closely tied is because of the important role our sense of smell has played in our species' evolution and safety.

Our olfactory system is also connected to an area of our brain called the limbic system. The limbic system is the area of the brain that is involved in the processing of emotions and memories. This connection to our limbic system and speed of processing information is another reason why researchers believe smell and memory are so closely tied.

Olfactory System and Social Behavior

Our sense of smell plays a large part in our lives. It even influences our culture and social behavior.

Smell plays a part in parenting behavior as well. Mothers and infants recognize each other's unique smell. This reinforces the bond between parent and child and contributes to the child's safety. Babies who recognize their mother's scent and are more likely to be comforted in her arms.

Considering how significant our sense of smell has been to our evolution and human experience, it can be surprising to learn that it is actually less sharp than the rest of our senses. We often have to be rather close to something in order to smell it. But we can be really far away from things and still see or hear them.

We also adapt to smell surprisingly fast. Walking into a café, we might be hit with a strong smell of coffee, but we don't go on smelling it that intensely for long. We might not even smell it at all by the time we leave.