Question;Name____________________________________________________Section________________Date;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.;Procedure;Taste;Taste involves several different kinds of sensory;cells located on the tongue and pharynx. Each kind of sensory cell responds to;specific kinds of chemicals. So there is not just one sense of taste, there are;several. We recognize at least five different kinds of taste senses: sweet;sour, salty, bitter, and umami (meaty).;Mapping;the Sense of Taste on the Tongue;1. Work with a lab;partner.;2. Obtain;a cotton swab and dip it into one of the solutions. The solutions are labeled;sweet, sour, salt, bitter, and umami (meaty).;3. Have;your lab partner touch the swab to the tongue at the following five locations: a.;the tip, b. right side, c. left side, d. center, and e.;back.;Place an X on;the following drawings of the tongue to indicate where you detected each;chemical.;a;a;A;a;a;c;d;b;d;b;D;b;d;b;d;b;c;c;c;c;e;e;E;e;e;Sweet;Sour;Salt;Bitter;Umami;4.;Test the other four solutions in;the same manner, but be sure to rinse your mouth with water after each;solution.;5. When you have;tested each of five chemicals, switch positions with your partner.;Results;1. Can you;detect each chemical at all places on the tongue?;2.;Compare your results to your;partner and other people in class. Do they detect the same chemicals in the;same place?;3. What does;this tell you about the sense of taste?;The Role;of Solubility in Detecting Taste;1. Dry;off the tip of your tongue with a clean paper towel. Place a few grains of;table salt (NaCl) on the tip of your tongue. Record the time interval from the;time you place salt on the tip of your tongue until you first taste the salt.;2. Dissolve;a few grains of salt in a small amount of water. Place this on the tip of your;tongue. Record the time interval from the time you place the salt solution on;the tip of your tongue until you first taste the salt.;Were the;two time intervals different? What does this tell you about the ability to;taste salty materials?;Touch;The sense of touch is made;up of a number of different types of receptor organs. Pressure, pain, heat, and;cold are all aspects of the sense of touch. We will experiment with some of them;here.;Localization;of Touch;You need a partner for;this exercise.;1. The subject;should keep his or her eyes closed throughout the exercise.;2. Touch;the skin on the back of the hand of the subject lightly with the pointed end of;a soft lead pencil. Be sure to leave a mark.;3. Then;ask the subject (with eyes still closed) to use a blunt probe to locate the;place on the skin where the stimulus was received.;4.;Use a ruler to measure as closely;as possible the error in locating where the stimulus was applied. Measure the;error in millimeters. Repeat five times at different locations on the back of;the hand.;5. Change roles;with your partner and repeat the experiment.;Results;and Conclusions;In the space provided;write a short paragraph that states your findings and conclusions.;Density of;Sense Organs;You need to work in pairs.;1. Have the;subject keep his or her eyes closed.;2. Use;a pair of forceps or calipers to gently touch the subject?s skin so that the;two points of the instrument touch with the same light pressure and at the same;time. Test the palm of the hand and two other regions of the body. Other;regions that may be tested are the back of the hand, the tip of the index;finger, the forearm, the tip of the nose, the forehead, and the back of the;neck. Not all of these need to be tried, but a decent selection should be made (at;least three locations).;3. Ask;the subject to state whether one or two points of the instrument are felt.;Repeat this procedure five times for each area of the body chosen. (To keep the;subject from guessing, the experimenter should occasionally touch the skin with;only one point. However, do not record the result of the response in your;data).;4.;Record your data in the following;manner: Record a minus sign (?) whenever two points were felt as one and a plus;sign (+) whenever the two points were actually felt as two.;5. Begin;with the points 20 millimeters apart and systematically decrease the distance;between the points from 20 mm to 15 mm to 10 mm to 5 mm. Find the smallest;distance at which the subject can still distinguish two points for each portion;of the body tested.;6. Change roles.;Record the data made on yourself as the subject.;7. From the data;estimate the comparative densities of touch receptors of the different parts of;the;body.;Area I;distance between points of forceps;in mm;Area II;distance between points of forceps;in mm;Area III;distance between points of forceps;in mm;Results;and Conclusions;Trial Number;1;2;3;4;5;20 mm;15 mm;10 mm;5 mm;Trial Number;1;2;3;4;5;20 mm;15 mm;10 mm;5 mm;Trial Number;1;2;3;4;5;20 mm;15 mm;10 mm;5 mm;1.;What is the smallest distance the;subject can still recognize two points for each of the three areas tested? Are;they the same? Explain.;Sensory cell;Skin surface;Nerve;to brain;2. Place;a sketch of your ?two-point device? on the drawing to indicate why two points;are sometimes felt as one.;3. Which;of the regions of the skin that you tested is represented by the left side of;the drawing and which is represented by the right side of the drawing? Explain;your answer.;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.;Detecting;the Blind Spot;Use the +;and dot below in the following manner. Close your left eye. Place the page;close to your face. Stare at the + with your right eye. Slowly move the page;away from you. What happens to the dot?;+;?;In order to detect the presence of an object;light must fall on the retina of the eye and stimulate either rods or cones.;There are no rods or cones at the point where the optic nerve goes;out;of the back of the eye. Use this information to explain what you observed when;looking at the + and ? above.;Hearing;The sense of hearing involves the detection of;sound vibrations. Airborne sounds cause the eardrum to vibrate. The eardrum is;attached to a series of three small bones: the malleus, incus, and stapes. The;stapes is attached to a membrane over a small opening in the cochlea. The;cochlea is fluid filled. Thus, the vibrations of the air are transferred to the;fluid of the cochlea. When the fluid in the cochlea vibrates, cells in the;cochlea are stimulated. When these cells depolarize, they send a signal by way;of the auditory nerve to the brain. In this part of the lab activity we will;explore some aspects of hearing.;Work with a;partner.;1.;Strike a low frequency tuning;fork (100 cps) and hold it near one ear. Determine how far from the ear the;subject can hear the tuning fork. Repeat with the other ear. Are both ears the;same?;2.;Strike the tuning fork and touch;the base of the vibrating tuning fork to the skull just in front of the;ear. Does the volume change?;How;is this sensation of hearing different from when the base of the turning fork;touches the skull near the ear?;3a. Have the subject sit with closed eyes. Strike;the tuning fork.;Have;the subject point to the position of the tuning fork. Repeat three times from;different positions.;Can the subject correctly identify the position of;the tuning fork?;3b.;Now have the subject keep eyes closed and plug one ear with a finger.;Have the subject point to;the tuning fork as it is struck at different positions. Was the subject able to;locate the position of the tuning fork accurately? Why was there a difference between the two;different trials?;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?;3. 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.;4. 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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