Chapter15

What are odorants?

Odorants are tiny little things in the air that have a smell.

They are different from other tiny things because they can float into your nose and stick to special smell sensors.

We have smell systems to help us:

  • find food

  • avoid danger (like smoke or rotten food)

  • enjoy nice smells

What is the trigeminal nerve?

The trigeminal nerve is like a helper that feels things in your face.

It works with smell and taste by noticing:

  • burning (like spicy food)

  • coolness (like mint)

  • tingling

So, it doesn’t just smell or taste—it feels!

How smell travels in your brain

  1. An odorant goes into your nose.

  2. It sticks to smell sensors high inside your nose.

  3. These sensors send signals to a place called the olfactory bulb.

  4. The signal travels deeper into the brain.

  5. It reaches thinking areas in the front of your brain, where you recognize the smell.

What is the piriform cortex?

The piriform cortex is a smell-thinking area in your brain.

  • The front part helps you tell smells apart.

  • The back part helps you remember and understand what smells mean.

What is an olfactory illusion?

An olfactory illusion is when your brain gets tricked about a smell.

Two examples:

  • If you see a picture of a lemon, you might think something smells sour even if it doesn’t.

  • A smell might seem stronger or weaker depending on what you expect.

This shows that your brain helps “decide” what you smell, not just your nose.

How taste travels in your brain

  1. Food touches your tongue.

  2. Taste buds detect the taste.

  3. Signals travel through nerves to the brainstem.

  4. Then to another brain area that organizes taste.

  5. Finally to the front of your brain where you understand it.

Taste vs. flavor

  • Taste is just what your tongue senses.

  • Flavor is the whole experience (taste + smell + texture).

The front part of your brain helps put all this together into flavor.

The five basic tastes

  • Sweet (like sugar)

  • Sour (like lemon)

  • Salty (like chips)

  • Bitter (like some vegetables)

  • Umami (savory, like meat or soup)

All parts of your tongue can taste all of these.

They help you survive:

  • Sweet = energy

  • Salty = body balance

  • Umami = protein

  • Sour = maybe spoiled

  • Bitter = could be dangerous

Tasters, nontasters, and supertasters

People are different:

  • Nontasters: don’t taste things very strongly

  • Tasters: normal tasting

  • Supertasters: taste things very strongly

This happens because of:

  • genes

  • number of taste buds

  • how they react to foods

What is anosmia?

Anosmia means you can’t smell.

It can happen if:

  • your nose is blocked or damaged

  • your brain’s smell areas are damaged

If the nose is the problem, smells can’t get in.
If the brain is the problem, smells get in but aren’t understood.

What is phantosmia?

Phantosmia is when you smell something that isn’t really there.

It is different from an illusion because:

  • illusions are real smells that get misunderstood

  • phantosmia is a completely made-up smell in your brain