Module 1
1. Module 1
1.21. Page 3
Module 1—The Nervous System
Taste
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To understand the sensation of taste, read “Taste” on pages 425 and 426 in your textbook. You may wish to make summary notes and support your learning with diagrams. Store this information in your course folder for reference.
taste bud: a sensory organ composed of a taste pore, taste cells, and sensory fibres of a sensory neuron involved in initiating taste sensations
When you smell the aroma of pizza, you may start to salivate. This means the aroma, or gases, from the pizza are dissolved in your mouth by saliva. Taste buds on the surface of the tongue can only detect a taste when chemicals, such as these gases, are dissolved on the tongue. The taste buds, or chemoreceptors, then send an impulse to the brain. Chemoreceptors detect four basic tastes—salty, sweet, sour, and bitter. “Figure 12.25” on page 426 of the textbook will give you a general idea of where various taste receptors are located on your tongue. To test it yourself, try resting a sour candy on various parts of your tongue.
Your taste likes and dislikes appear to have a homeostatic value. They may be an indicator of what the body needs to retain or they may help to restore homeostasis. For example, a liking for sugar and salt helps satisfy the body’s need for carbohydrates, minerals, and some amino acids. Because many poisons and spoiled foods are bitter, a person’s dislike of bitter food is an instinctive, protective response.
Self-Check
SC 1. What four basic tastes do most scientists agree are sensed by most people? Name at least one food that illustrates each taste.
SC 2. Supertasters are people whose sense of taste is significantly more sensitive than the average person's. Hypothesize how the anatomy of taste reception may differ in a supertaster as compared to a person with an average sense of taste.
SC 3. Explain why the taste bud is considered a “sense organ.”
SC 4. Hypothesize whether the taste buds that are sensitive to saltiness are the same taste buds that are sensitive to bitterness or sweetness.
SC 5. Draw a flow chart to illustrate the steps from taste reception to interpretation.
Self-Check Answers
SC 1. Most people are able to taste salty, sour, sweet, and bitter.
- A salty taste is mostly due to sodium ions, as in table salt. Calcium ions can also produce the salty taste.
- A sour taste is due mainly to the presence of hydrogen ions as in most acidic foods, including oranges, lemons, and tomatoes.
- A sweet taste is perceived when sugars and some proteins are present.
- A bitter taste is characteristic of coffee, unsweetened chocolate, beer, uncured olives, tonic water, and aspirin.
SC 2. Supertasters may have more papillae, more taste buds, or more taste cells in the taste buds than the average person.
SC 3. A taste bud is considered to be a sense organ because it is composed of several types of cells, such as the taste cell with its modified ending of hairs, and the sensory neuron, which is depressed into a pore where it captures chemicals from foods. The cells work together to initiate the nerve impulse.
SC 4. Taste buds sensitive to saltiness may be different than those sensitive to sweetness or bitterness because they may have different receptors on the hair portion of the taste cell that different chemicals fit into.
SC 5. Chemoreceptors in taste buds detect chemicals in food that trigger sensory neurons to communicate nerve impulses to the brain. There, the parietal lobe, which is located in the cerebrum, interprets these impulses as a sensation.