Our Sense of Smell

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Background

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 surrounds. Molecules are carried through the air into our nose and nasal passage, landing on a lining called the olfactory epithelium. Olfactory receptors (specialized neurons) located on the epithelium recognize and bind with specific molecules. When triggered, these neurons send messages to the olfactory cortex in the brain.

Other neurons in the olfactory cortex make sense of the chemicals detected and communicate information about the odor to the conscious and thinking portions of the brain.

The sense of smell also is closely related to memory. Have you ever smelled something that evoked a childhood memory, a location or an experience? The proximity of the olfactory cortex to the amygdala and hippocampus is believed to be the reason. The amygdala is responsible for emotional memory and the hippocampus regulates working and short-term memory.

Guiding Question

How does our sense of smell work?

Setup

For each group of students, empty one envelope of grape, lemonade, orange and cherry into separate re-sealable plastic bags.

Make copies of the Let’s Get Fruity student page on cardstock.

Fill six paper cups half full of water.

Procedure

Part 1

  1. Ask students to locate their noses by pointing with their fingers. Ask, What does our nose enable us to do? Discuss all ideas.
  2. Give each student a mirror and ask him or her to closely exam his/her nose. Point out that they have two openings called nostrils that allow air to enter their nasal passages. Point out that the nose also is important for breathing. Have students inhale and exhale slowly to become aware of how air enters and leaves the nose. Show or draw a diagram of the inside of the nose and share it with students.
  3. Tell students to draw a picture of their noses in their notebooks.
  4. Give each group of four students a set of soft drink mix powder in small re-sealable plastic bags. Let each student hold one of the bags. Instruct students not to open the bags. Ask students to predict what the powder in their bags might smell like, and discuss their predictions with their group or shoulder partner. Ask, On what did you based your predictions?
  5. Next, without opening the bag, instruct students to smell the bag. They should not be able to smell the contents.
  6. 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.
  7. Tell students they will try to smell the powders with the bags open. First, show students how to carefully open the bag, keeping the powder in the bottom. Demonstrate how to properly smell a substance by using your hand to waft (gently back and forth motion) the scent to their noses.
  8. Let each students open his or her bag, and waft the scent to his or her nose to identify it. Have students pass the bags around to each group member, so that each student can smell all of the substances. Let students share what they have discovered about the substances.
  9. Ask, Can you identify the scents? Have you ever smelled anything similar before? If they haven’t identified the scents you can inform students that they smelled orange, cherry-, grape- and lemon-flavored soft drink mixes.
  10. Tell students that all scents are made of small particles/chemicals that mix with the air. The small particles float in the air and enter the nose. When this happens, the nose detects the particles and sends a message to the brain. Our brains help us recognize, remember, and identify scents.
  11. Review with students that the scents they smelled are collected inside the nose and a message is sent to the brain. Have a student add a piece of yarn from the nose to the brain on the class body diagram.
  12. If you are not conducting Part 2 immediately, have students reseal the bags to keep the contents fresh for later use.

Part 2

  1. Tell students that they will use the powdered soft drink mix to create artwork that smells delicious. Give each group 4 small paper cups, a half-cup of water and 4 spoons. Ask each member of the group to take one of the bags of powdered drink mix, and carefully add one spoonful of water to the bag. Seal the bag and gently mix, so that the powder dissolves into the water in the bag. They now will have created “Smelly Paint.”
  2. Instruct students to carefully pour the “paint” into a small paper cup, or pour the “paint” for students.
  3. Give each student 4 cotton swabs (“paintbrushes”). Remind them to use each cotton swab with only one color.
  4. Give each student a copy of the “Let’s Get Fruity” page. Ask students to pick a crayon that matches the fruit and then outline the fruit with the crayon. Tell students that they will paint the fruits with the corresponding paints. For more fragrant pictures, encourage students to paint two layers on each picture.
  5. Allow the paper to dry. Then, demonstrate how to activate the smell in the painted areas, by gently scratching the dry paint.
  6. Ask students, What parts of the body and systems enable you to smell? Have students refer to the body diagram, if needed. Students should understand that nerve connections between the nose and the brain are necessary for the sense of smell.

Extensions

  • Invite students to create original “Smelly Paint” pictures.
  • Use an orange and peel the skin in front of the class. Ask students to raise their hands when they smell the scent of the orange. Stand in front of a fan or other source of moving air and peel a second orange. Have students predict whether this will affect the distribution of orange scent in the room.
  • Conduct the same activity with another orange outdoors. Ask, Can you still smell the orange? What about inside the classroom? Is the orange scent still detectable? Help students understand that air circulation and currents affect the distribution of particles in air and our abilities to smell them.

Books:

Smelling: the Five Senses by Rebecca Rissman
Let’s Get Fruity!

 

fruits chart

 

Name: _____________________________nose science