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Sense of Smell and Olfactory Fatigue

A Carolina Essentials™ Investigation

Overview

This quantitative investigation provides students with an introductory sensation and perception activity. The activity can be used as a unit introduction for human senses or as a stand-alone olfactory sensation activity. Students use fragrant oils to determine the time of olfactory fatigue for both of their nostrils and then examine the link between smell and memories. If time permits, class olfactory fatigue data may be analyzed to examine class averages or look for the possibility differences based on genetics, medical conditions, or life style.

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Grade & Discipline
9-12

Life Science. Recommended for grades 9-12.

Time Requirements
Prep15 min
Activity5 days, 95 min

Teacher Prep time: 15 min
Student Time: 30-45 min

Safety Requirements
Safety Goggles Required

Overview

This quantitative investigation provides students with an introductory sensation and perception activity. The activity can be used as a unit introduction for human senses or as a stand-alone olfactory sensation activity. Students use fragrant oils to determine the time of olfactory fatigue for both of their nostrils and then examine the link between smell and memories. If time permits, class olfactory fatigue data may be analyzed to examine class averages or look for the possibility differences based on genetics, medical conditions, or life style.

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Teacher Notes
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Student Worksheet

Essential Question

How do structures in the body enable human beings to sense their environment?

Investigation Objectives

  1. Investigate the time for the onset of olfactory fatigue.
  2. Determine if odors trigger memories.

Next Generation Science Standards* (NGSS)

Science and Engineering Practices

Practice: Developing and Using Models

  • Develop and use a model based on evidence to illustrate the relationships between systems or between components of a system.

Disciplinary Core Ideas

DCI: LS1.A: Structure and Function

  • Multicellular organisms have a hierarchical structural organization, in which any one system is made up of numerous parts and is itself a component of the next level.

Crosscutting Concepts

Concept: Systems and System Models

  • Models (e.g., physical, mathematical, computer models) can be used to simulate systems and interactions—including energy, matter, and information flows—within and between systems at different scales.

Safety & Disposal

Students should wash their hands after entering and before exiting the lab. Students should be in safety glasses to conduct the investigation. Supervise students conducting the tasting activity.

Place all cotton swabs in a re-sealable bag and dispose of them in accordance with your school chemical hygiene plan.

Procedures

Student Procedures

Procedures and Disposal

Teacher Preparation and Tips

Student:

Teacher:

  1. Place a cotton swab in an Erlenmeyer flask vertically. The head of the swab should be above the rim of the flask.

The Essential Question may be used to engage students in the laboratory investigation and to help them identify what they learned from the experience.
Ask students what “nose blind” means.

  1. Place the flask and swab on a level surface approximately 30 centimeters (1 foot) away from and just below the nose of the test subject.


You may want to place small dropper bottles of oil at lab stations for faster dispensing.

  1. Have the test subject close his or her left nostril by pressing on it with the left index finger.

Check the placement of the swabs. Cotton side up and about 1 foot from the nose.

  1. Place two drops of clove oil on the head of the cotton swab.


Demonstrate the wafting technique.

  1. Start the timer and have the subject gently waft the odor toward his or her nose, gently fanning with the right hand and inhaling through the right nostril, then exhaling through the mouth.

Ensure students start timers quickly.

  1. The subject will continue to sniff the odor and exhale through the mouth at a normal rate until the smell is no longer detectable or has greatly diminished.

Make sure students are not moving the swab.

  1. Record the elapsed time in minutes and seconds in the data table below.

Make sure the time is reset to 0 before the next step begins.

  1. The subject should release the left nostril, close the right nostril with the right index finger, and waft the odor of the clove oil toward his or her nose with the left hand.


Demonstrate how to record minutes and seconds.

  1. Start the timer.
  1. The subject should continue to sniff the odor and exhale through the mouth at a normal rate until the smell is no longer detectable or has greatly diminished.
  1. Record the elapsed time for the left nostril in minutes and seconds in the data table.

Reinforce that the re-sealable bag must be completely sealed so odors do not mix.

  1. Places the used swab in a re-sealable plastic bag, and seal the bag completely.

  1. Repeat the procedure using the peppermint oil, and record the results in the data table.

If time permits, combine individual data and calculate the class average. Ask students what genetic, medical, or life style factors they think may influence the olfactory fatigue time. Differences in gender, ethnicity, allergy diagnosis, or whether parents smoke could be interesting factors to look at.

  1. Switch roles and repeat the process until everyone in the group has been tested.

Data and Observations

Times will vary based on room conditions.

Fragrance Right Nostril Fatigue (min and sec) Left Nostril Fatigue (min and sec)
Clove Oil 1:22 1:15
Peppermint Oil 1:38 1:45

Analysis & Discussion

  1. Was the peppermint oil smelled immediately after the diminished odor of the clove oil? What is the explanation for the nose’s ability to detect new or different odors?

    Yes. The nose remains immediately sensitive to any new or different odor.

  2. How do the fatigue times of the clove oil and peppermint oil compare when sniffed in succession with the right nostril?

    The times are approximately the same.

  3. Is the fatigue time for the left nostril significantly different than the right nostril?

    The fatigue times should be similar.

  4. When you smelled the cloves and the peppermint, did you recall any memories associated with those odors? If so, briefly describe them.

    Student answers will vary.

  5. Diagram the process of smelling the peppermint oil.

    In the human body, specialized nerve cells respond to conditions in the environment and send a signal through other nerve cells to the brain. These specialized nerve cells have structures called sensory receptors, structures that will only respond to a specific kind of stimulus. For each type of receptor, nerve cells provide information in the same “all or nothing” manner. A stimulus is either sufficient to cause a cell to fire, transmitting a nerve impulse to the brain or spinal cord, or it is not. For instance, a light receptor cell in the eye may respond only to red light. If a light receptor for red light “sees” red, it discharges. Although air is always around you, you do not feel the air unless it is moving over your skin in the form of a current or as wind.

    Nerve impulses travel through nerve fibers to the brain, where the impulses are processed. By analyzing all the inputs from the sense organs, the brain interprets the appropriate responses, which we perceive as seeing, feeling, hearing, smelling, and tasting. If an injury causes the nerves in a sense organ to be damaged or severed, the brain can no longer obtain accurate information from that nerve, even if the sense organ is healthy and might be receiving impulses from stimuli.


    Step 1: Source releases aromatic compounds
    Step 2: Aromatic compounds are trapped by the mucus lining in the nose.
    Step 3: The sensory receptors in the nose are triggered.
    Step 4: Nerve impulse is sent to the brain.
    Step 5: Nerve impulse is interpreted.

*Next Generation Science Standards® is a registered trademark of Achieve. Neither Achieve nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of, and do not endorse, these products.