by Ron Kurtus (revised 29 August 2005)
You sense odors and aromas with your nose, which can detect thousands of smells. The sense of smell is important in that it gives subtle signals of the surrounding environment.
Animals usually have a more sensitive sense of smell than humans.The nose works similar to a smoke detector in being activated by certain molecules.
Smell and taste often combine to determine flavors in foods. Smells can also trigger vivid memories in people.
Questions you may have include:
- Why is the sense of smell important?
- How does the nose work?
- What are some unusual characteristics of smell?
This lesson will answer those questions.
Importance of smelling
Just like the other major senses, the sense of smell has an important place in a person's or animal's life.
You can determine much about the environment around you through the sense of smell.
One important area is determining when food has spoiled or is not good to eat. Smell, along with taste, help you enjoy food.
People give off various odors. Being sensitive to their smells, you can tell a lot about the person, including his or her state of health. There are also sexual odors, bad breath, flatulence, urine smell that can be detected.
Animals use their sense of smell much more than humans do. They use it to tell if any of their species has been in the neighborhood recently. It is also used in tracking prey. Male animals use their sense of smell to determine the sexual receptiveness of females.
The sense of smell in dogs is about 1000 times better than humans. That means it takes less molecules for them to detect the smell. Recently researchers have found that dogs can detect the smell of cancerous growths in humans.
Male moths only require a few dozen molecules to detect that a female moth is in the vicinity. They use their sensitive sense of smell to navigate toward the potential mate.
Ants use smell to mark their path. Mice do the same thing.
The nose is the sense organ that detects chemical odors sends those signals to the brain for processing. There are at least 100,000 different scents. A normal person can tell the difference between 4000-10,000 smells.
Molecules are released from most objects, allowing you to smell them. Flowers.
How nose works
The way the nose works is that scent molecules mixed in the air are breathed in and come into contact with olfactory cells at the top of the nasal cavity deep inside your nose. If the molecule has correct characteristics, it temporarily attaches to the cell, causing a signal to be sent to the brain, where it is processed and gives you the indication what smell is being sensed.
Similar to smoke detector
The nose works similar to the way a smoke detector works. In a smoke detector, certain molecules trigger a sensor, which cause electrical signals to travel through a wire to a circuit card for processing, thus setting off the alarm.
Obviously, the operation of the nose is much more complex. It is also much more flexible and does not require batteries.
Smell often combines with taste to sense flavors. Certain smells can trigger memories.
Smell and taste
The sense of smell and that of taste often work in coordination. When eating some food, the tongue identifies the taste of the food, and the nose identifies its smell. Both sensations are communicated to the brain, which combines the information to give the impression of a flavor.
While tastes such as salty, bitter, sweet and sour can be recognized without the sense of smell, more complex flavors such as from fruits require both taste and smell to be recognized. You can try this with by eating flavored gelatin while holding your nose to prevent smelling the food. Doing this makes it difficult to determine the flavor of the gelatin.
For some reason, certain smells can trigger memories and feelings. A person may smell a specific odor or aroma from the past, and vivid memories of the event and people involved will suddenly come alive in the brain. Some people have even started crying when a particular smell triggered a distant memory and the feelings involved with that occasion.
Scientists aren't sure why this occurs, but it also happens with songs to a lesser degree. Memories don't seem to be triggered by tastes or input to the other senses.
Your nose senses odors or smells. A human can detect thousands of smells. Molecules trigger the sense of smell in the nose. Dogs have a sense of smell 1000 times more sensitive that humans. Smell and taste often combine to determine flavors in foods, and smells can also trigger memories.
Be aware of the environment around you
Resources and references
Olfaction - Technical description of smell from chemical company
Smell Theme Page - Links to various smell resources
When Doctors Used to Smell - Smelling used in health care
Questions and comments
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