Sensory Function Touch, Taste and Smell

1.  Distinguish between general and special senses. 
2.  Explain why receptors respond to specific stimuli and how the organization of a receptor affects its sensitivity. 
3.  Identify the receptors for the general senses, and describe how they function. 
4.  Describe the sensory organs of smell, and trace the olfactory pathways to their destinations in the brain. 
5.  Describe the sensory organs of taste, and trace the gustatory pathways to their destinations in the brain.

You will be given a role to play in a short skit about sensory receptors.  Dr. Henry is the director of the skit.  Your role will either be stimulus or receptor.  If you are a receptor, join the other receptors and organize yourselves in anatomically correct positions (the head is nearest the projection screen in the front of the classroom).  Meanwhile, the stimuli should decide what to do when they are called to action. 

Activity B: Gustation and Olfaction Stations 

Proceed through the stations. 

Station 1:  Olfactory Receptors --  

Get a model and the attached diagram of the olfactory receptors. 
 

  Label the anatomical features of the olfactory receptors. 
 

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Station 2:  Olfactory Adaptation -- Procedure 
 

1.  The subject should close his/her eyes after plugging one nostril with cotton.

2.  Hold one of the odorous substances under the subject’s nose. 

3.  The subject should breath through the nose and out of the mouth.  Note the time it takes for the odor to disappear. 

4.  As soon as olfactory adaptation has occurred, test an entirely different substance. 

5.  Compare results for the three substances. 

6.  If time allows, test a second subject.

 
  1. Explain in writing the mechanism of olfactory adaptation. 
 
2. Did any of the substances cause tearing?  If so, provide an anatomical explanation for the tearing and put it in writing. 
 
 

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Station 3:  Gustatory Receptors --  
 

Get a model and the attached diagram of the gustatory receptors. 

  Label the anatomical features of the gustatory receptors. 

 

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Station 4:  Identifying Taste Zones -- Procedure 
 

1.  The subject thoroughly dries his/her tongue. The experimenter places some granulated sugar on the tip of the tongue.   
 
Record how long it takes for the individual to taste the sugar.

2.  Repeat the experiment, but use sugar dissolve in water solution. 
 

Again record how long it takes the person to taste the solution.
 
  Explain in writing the difference in time for the person to taste the solution.
 

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Station 5:  Taste and Inheritance -- Procedure 
 

1.  Place a few crystals of phenylthiocarbamide (PTC) on the tongue of the subject.  Ask the subject if she/he tastes anything.  If so, describe the taste. 

2.  Repeat experiment for each individual in the group. 

3.  Report the numbers of PTC tasters and non-tasters to Dr. Henry. 

  Explain in writing why some individuals can taste PTC and other cannot. 
 

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Station 6:  Taste and Smell -- Procedure 

1.  The subject dries his or her tongue, closes his or her eyes and pinches his or her nostrils. The experimenter places one of the cubes of food, on the subject’s tongue. 

2.  The subject tries to identify the taste: 
 
 

  without chewing 
 
  after chewing (nostrils closed) 
 
  after chewing (nostrils open) 
 
3.  Repeat experiment for each group member, try different substances so that the subject doesn’t know which one is coming. 
 
  1.  Create a table using the following template. Record results for each team member. 

Subject Name	Food Item	Without chewing	Chew, close nose	Chew, open nose

2. Explain the results of the experiment.