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