1. The Sense of Smell



Download 61 Kb.
Date03.05.2018
Size61 Kb.

CHAPTER 15: THE CHEMICAL SENSES

1. The Sense of Smell

2. Olfactory System

3. Taste System

4. Anti-Sweet Tooth Gum

1. The Sense of Smell

The olfactory system provides our sense of smell. Our sense of smell can be diminished by multiple causes. Infection or prescription drug side-effects may negatively influence our sense of smell. As we age, there is a normal decline in our ability to detect and recognize different scents. When one experiences a loss of the ability to smell that is greater than expected with normal aging, however, may serve as an early marker for the onset of neurological disease.


This ABC news feature discusses how smell influences behavior and possible links between the ability to smell and disease.
RESULTS & DISCUSSION
1. According to the video, how many Americans are affected by loss of smell? What potential diseases appear to be related to loss of smell?

2. What is meant by the statement that the ability to smell is “hardwired in the brain” before we are born? Describe the examples of evidence for this claim that were provided in the movie. Why do you think it would help humans to be born with the sense of smell?

3. List and describe the practical uses of smell discussed in the video. Describe another, novel, potential use of smell.

2. Olfactory System

The olfactory system provides our sense of smell. Some substances produce volatile molecules that stimulate the olfactory system. Because the chemical composition of the stimulus is critical to whether olfaction occurs, olfaction is called a chemical sense.


The receptor structures for olfaction are located in the olfactory epithelium at the top of the nasal passages. Projections of the olfactory receptor neurons extend into the mucous layer covering the olfactory epithelium. Odorant molecules make contact with the mucous layer of the olfactory epithelium, where they stimulate the olfactory receptor neurons.
Actually, there are some additional steps and structures involved in the creation of an olfactory response beyond those described above. This lab provides practice identifying the components of the olfactory system. Drag and drop the labels to their appropriate locations in the diagrams of the olfactory system. If you are incorrect, the labels will not stick. The first diagram is the most general. Click on the arrows to proceed to increasingly detailed views of the system.
RESULTS & DISCUSSION
1. How do the cilia relate to the olfactory receptor neuron? What is the olfactory receptor, and how does it differ from the olfactory receptor neuron?

2. Where does chemical stimulation produce an exchange of ions?

3. Why do you think a bad head cold affects the sense of smell? Be sure to use the olfactory structures featured in this exercise to explain.

3. Taste System

As for the olfactory system, a series of diagrams are presented. Drag and drop the labels to their correct locations for each diagram. If the label is incorrect, it will not stick. The diagrams become progressively detailed as you proceed through the lab.


RESULTS & DISCUSSION
1. Describe the structure of a taste bud. Where are taste buds located (be specific)?

2. Which structure contains the actual receptors for taste, and where are the receptors located in this structure? What determines whether a substance will stimulate a particular receptor?

3. Describe the sequence of events from taking a drink of orange juice to tasting that orange juice. Use the information from this exercise.

4. Anti-Sweet Tooth Gum

This ABC video describes a type of gum that eliminates the perception of sweetness in an attempt to decrease the reward, or positive response, associated with eating sweet foods.


RESULTS & DISCUSSION
1. How does the gum discussed “numb” the sweet tooth? How long does this effect last?

2. Can people who chew this gum taste flavors other than sweetness after chewing the gum? Describe why you think they can or cannot based on how taste receptors function.



3. The active ingredient in the gum is a substance called Gymnema Sylvestre, which has a molecular structure similar to that of glucose. These molecules fill the receptor locations normally filled by glucose on the taste buds thereby preventing its activation by sugar molecules. Using this information, plus what you know about specialized taste receptors, relate the effect of this gum to current research on taste receptors.



Virtual Lab Manual



Share with your friends:


The database is protected by copyright ©dentisty.org 2019
send message

    Main page