Devry SCI214 week 7 ilab

08 Jun Devry SCI214 week 7 ilab

Question
Week 7: Sensory Abilities

Invitation to Inquiry

There are many kinds of eye-glasses used for special purposes. People who fish like to wear polarizing sunglasses. People who shoot guns competitively, typically wear amber colored glasses. Conduct some research to determine why each prefers a particular kind of eye-wear.

Background

This laboratory exercise gives you an opportunity to study how we sense changes in our surroundings. Your ability to sense changes in your surroundings involves (1) the specific ability of sense organs to respond to stimuli (detection), (2) the transportation of information from the sense organ to the brain by way of the nervous system (transmission), and (3) the decoding and interpretation of the information by the brain (perception). In order for us to sense something, all three of these links must be functioning properly. For example, a deaf person might be unable to detect sound because (1) there is something wrong with the ear itself, (2) the nerves that carry information from the ear to the brain are damaged, or (3) the portion of the brain that interprets information about sound is not functioning properly. While this laboratory activity focuses on the function of sense organs, it is important to keep in mind that the peripheral and central nervous systems are also important in determining your sensory ability. All sense organs contain specialized cells that are altered in some way by changes in their environment (stimuli). The sensory cells depolarize and since they are connected to nerve cells, they cause the nerve cells to which they are attached to depolarize as well, and information is sent to the brain for interpretation by way of nerve pathways.

In this lab exercise you will:

1. Make a map of the location of different kinds of taste buds on your tongue.

2. Determine several characteristics of the sense of “touch.”

3. Locate different kinds of temperature sensors in the skin.

4. Study several aspects of visual acuity.

5. Study several aspects of the sense of hearing.

Temperature Sense–Detecting Hot and Cold

Work with a partner.

1. With a pen, draw a square with 20 mm sides on the back of the subject’s hand, then subdivide this square into 16 smaller squares by dividing each of the sides into 5 mm segments.

2. Have the subject keep eyes closed and place his or her hand flat on the table.

3. Obtain a nail that has been in ice-cold water. Dry it off with a paper towel.

Lightly touch each of the squares of the grid on the hand at random. The subject should respond by saying “cold” if such a sensation is actually felt; otherwise the subject remains silent. It is important for the subject to ignore the sense of touch and concentrate on the sensation of cold.

4. For every positive response, the experimenter marks a plus sign (+) on the following grid at a point corresponding to the point tested on the skin.

5. Be sure that the nail is really cold when you make each test.

6. Repeat this exercise with a very warm nail and record your results on the second grid.

Cold Warm

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7. Switch roles with your partner and repeat the exercise.

8. Answer the following questions.

Do you detect hot in every square?

Do you detect cold in every square?

Are hot and cold receptors always located in the same squares?

Do the same receptors respond to hot and cold? Explain how you know.

Temperature Sense—Detecting Changes in Temperature

1. Dip one finger into a beaker of hot water and at the same time put a finger from the other hand into cold water.

2. After 30 seconds, transfer both fingers into a third beaker of warm water.

Results and Conclusions

Describe the sensations of both fingers in the beaker of warm water and explain why there is a difference in sensation.

Vision

The eye is a complex structure that focuses light on cells of the retina that respond to changes in light. There are two kinds of light receptors; rods and cones. Rods are very sensitive to light and only respond to differences in light intensity. The cones are less sensitive to light. There are at least three kinds of cones, each of which responds to specific colors of light. The rods and cones are located in different places in the retina of the eye. In this part of the lab activity you will make a number of observations about the eyes and their response to various stimuli.

Determining the Location of Rods and Cones

Rods and cones are not located in the same place on the retina of the eye. When you look at things from directly in front of the eye, the cornea and lens of the eye focus the light on a region known as the fovea centralis. When you look at things with your peripheral vision, the light is focused on regions of the eye other than the fovea centralis.

Work with a partner.

1. Choose three similarly colored squares of paper about 100 cm by 100 cm.

2. Have your partner stare at a distant object directly in front of him or her.

3. Start behind your partner (out of the field of vision) and slowly move the piece of paper forward at eye level about 30 cm to the side of the head.

4. Ask your partner to tell you when the piece of paper is first seen and when the color of the paper can be detected.

Use the information about the location of rods and cones and the results you just obtained to answer the following questions.

Which sense organs (rods or cones) are most common in regions outside the fovea centralis?

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Which sense organs (rods or cones) are most common within the region of the fovea centralis?

.gif”>Explain how this experiment allows you to answer these questions.

Sensory Abilities

Name ___________________________________________ Lab Section____________________

Your instructor may collect these end-of-exercise questions. If so, please fill in your name and lab section.

End-of-Exercise Questions

1. Describe the regions of your tongue that are most sensitive to sweet, sour, salt, bitter, and umami.

2. How is solubility important to the sense of taste?

2. Determine the average distance between points on the palm of the hand at which persons in the class correctly identified that they were being touched by two points. On the average, individuals

could discriminate between two points that were _____ mm apart..gif”>.gif”>

3. Using the data you collected for different parts of the skin, rank them according to which had the greatest density of touch receptors and which had the lowest density.

5. Write a paragraph describing what you learned about the receptors that respond to temperature. How many kinds of receptors are there? Explain how you know there are different kinds of receptors.

6. There are some kinds of people who can see well in bright light but are not able to see in dim light. This condition is called “night blindness.” What kinds of sensory cells do not function to capacity in individuals who have night blindness?