The Sense of Smell: Olfactory Bulb and the Nose

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  • 0:06 The Smell of Good Food…
  • 1:28 The Olfactory Epithelium
  • 2:08 Odor Solubility
  • 2:48 The Olfactory Nerve
  • 3:19 The Olfactory Bulb
  • 4:15 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

How does the sense of smell relate to your eyes? Why can we smell something in the first place? These questions and many more will be answered as we look into the olfactory bulb, chemoreceptors, cranial nerve I, and the olfactory nerve.

The Smell of Good Food

The olfactory bulbs, which allow us to sense smells, are located right between the eyes.
Olfactory Bulbs between Eyes

Ah, the smell of something delicious, especially when we're hungry. It brings a smile to one's face. We can even smell mom's great home cooking all the way up on the second floor. We begin to salivate and think of all the great tastes we'll soon experience. Then we run downstairs to savor the smell, taste, and look of some tasty food. The ability to sense these delicious smells depends on special receptors and nerves, some of which are right between your eyes!


When your mom is cooking your favorite meal, the food releases certain chemicals that fly up into the air. Eventually these chemicals disperse all around the kitchen and then throughout the entire house. As you sit upstairs, watching the videos on your screen, some of these molecules begin to reach your nose and travel way up into it.

These molecules are able to be recognized by special sensory nerves known as chemoreceptors. Chemoreceptors are receptors that are able to sense external chemical stimuli such as odor molecules or molecules that produce the sensation of taste.

The Olfactory Epithelium

Odor molecules enter through the nose and travel to a patch of chemoreceptors near the eyes.

As the odor molecules enter your nose they travel up and back to a little patch of chemoreceptors located underneath and in the middle of the place where your eyes sit in your skull. This little patch is called the olfactory epithelium, and it has a bunch of chemoreceptors in it.

Just in case you were wondering, the word 'olfactory' refers to our sense of smell, technically called olfaction.

During the process of olfaction, odor molecules entering your nose will latch onto the chemoreceptors in the olfactory epithelium. However, there's a small catch.

Odor Solubility

The olfactory epithelium involved in the first step of the sense of smell has a mucous layer covering the chemoreceptors. This mucous layer implies that only water-soluble odor molecules will be able to pass through it easily and activate the chemoreceptors involved in the sensation of smell. However, the mucous layer also has proteins, appropriately called odor-binding proteins, that help to transport non-water-soluble molecules through the mucous and to the chemoreceptors so they can activate the chemoreceptors as well.

Odor-binding proteins allow non-water-soluble molecules to pass through the mucous layer.
Mucous Layer in Olfactory Epithelium

The Olfactory Nerve

The entire collection of chemoreceptors, in our specific case called olfactory receptor neurons, as well as their projections called axons are known as the olfactory nerve. The olfactory nerve, one on either side of your body, is also known as cranial nerve I. The olfactory nerve is the most important nerve involved in the sensation of smell.

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