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K-1: The Senses

Author(s): Barbara Tharp, MS, Michael Vu, MS, Delinda Mock, BA, Christopher Burnett, BA, and Nancy Moreno, PhD.

Our Sense of Smell

Guiding Question
How does our sense of smell work? 

Concepts

  • All of the senses are connected to the brain. 
  • Our senses let us know what is going on inside and outside our bodies. 
  • One of our senses is smell (olfaction). 
  • Our noses detect, or smell, very small particles in air.Information is sent from the nose to the brain, which helps us to experience, remember and recognize smells. 


Much like taste, the sense of smell allows us to detect chemicals in the environment. In fact, smell and taste often work together to gather information about our surroundings. Flavor is a perception that is based on input from taste, smell and even touch.

With the sense of smell, molecules carried through the air and into the nose land on the moist lining (olfactory epithelium) of the nasal passages and bind to olfactory neurons in the lining. The binding process triggers these neurons to send messages directly to the olfactory bulbs in the brain, and on to the olfactory cortex. Information about odors being detected also is sent to the thinking portion of the brain. 

The olfactory system enables humans to distinguish among thousands of odors, all of which are classified into six major groups: floral, fruity, spicy, resin, burnt and putrid. 

The sense of smell is closely related to memory and emotions. Have you ever smelled something that evoked a childhood memory, a location or an experience? Scientists believe these associations are due to the close proximity of the olfactory cortex to the amygdala and hippocampus. The amygdala is responsible for emotional memory and the hippocampus plays an important role in consolidation of information from short-term memory to long-term memory and spatial navigation.


Procedure: Part 1

Ask students to locate their noses by pointing with their fingers. Ask, What does your nose enable you to do? Discuss all ideas.

Give each student a mirror and ask him or her to closely examine his/her nose. Point out that our noses have two openings, called nostrils, which allow air to enter the nasal passages. Emphasize that the nose is critical for breathing. Have students inhale and exhale slowly to become aware of how air enters and leaves the nose. Show a diagram of the inside of the nose, or draw one for the class. 

Ask students if they have ever really looked at his/her nose. Give each student a mirror to closely examine their the nose. Have students draw their noses in their notebooks, and label the outer parts.

Give each group of students a set of four flavors of soft drink mix powder in small re-sealable plastic bags. Let each student hold one bag, but instruct students not to open the bags. Ask them to predict what the powder in their bags might smell like, and discuss their predictions with their groups. Ask, On what did you base your predictions? 

Next, instruct students to smell their bags, but not open them. Students should not be able to smell the contents.

Ask, Were you able to check your predictions with the bag closed? Why do you think you can’t smell the powders in the bags? Invite students to share their ideas. 

Tell students they will try to smell the powders again, with the bags open. Show students how to carefully open a bag, keeping the powder in the bottom. To demonstrate how to properly smell an unknown substance, gently wave your hand and-forth over the open bag. This is called wafting.

Let each student open his/her bag, and waft the scent to his/her nose to identify it. Have students pass their bags around their groups, so that each student can smell all of the substances. 

Ask, Can you identify the scents? Have you smelled anything similar before? If they haven’t identified the scents, inform students that they smelled orange-, cherry-, grape- and lemon-flavored soft drink mixes.

Tell students that all scents are made of small particles/chemicals that mix with, and float in the air. When these particles enter our nasal passages, they are detected by neurons in the nose, which send a message to the brain. Our brains then help us to recognize, remember and identify scents.

Review with students that the scents they smelled are collected inside the nose, and are identified via messages sent to the brain. Have a student add a piece of yarn from the nose to the brain on the classroom human body diagram.

Note: If you are not conducting Part 2 immediately, have students reseal the bags to keep the contents fresh for later use.

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