What is the Temperature Sensation You Feel in each of Your Hands after Immersing Them in the Room Temperature Water?

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Is there an apparent difference in hearing between your two ears?

 

SKU: Repo1842399

Lab 5: Senses

Objectives

  • To locate the blind spot and determine the accommodation in the eye
  • To detect the location of sound
  • To investigate the density of touch receptors on various parts of the body
  • To investigate heat and cold receptors in the skin
  • To investigate how taste and smell interact

 

Materials

  • ruler or measuring tape
  • pencil
  • calculator
  • tuning fork and rubber stopper (supplied to you)
  • two toothpicks (or a hairpin)
  • 2 bowls (or pans) large enough to immerse one of your hands into
  • 1 bowl (or pan) large enough to immerse both hands into simultaneously
  • a bag of multi-flavored Life Savor candies (or Starbursts, or any other multi-flavored candies)
  • volunteers willing to participate (friends, relatives, neighbours, spouses, etc.)

 

Description of the problem

This lab will investigate the senses of sight, hearing, touch, taste, and smell. You’ll need to enlist volunteers. One person will be needed to help you when you undergo the experiments. Additionally, you are to perform some of these experiments on your volunteers for comparison purposes.

Experiment: Determining the blind spot in each eye

Light rays enter the eye and strike rod and cone cells, which are the photoreceptors for sight. Rods and cones generate nerve impulses that travel to the brain via the optic nerve. However, no photoreceptors are found on the retina where the optic nerve leaves the eye. This area is called the blind spot. Click here for a few simple experiments regarding the blind spot.

You’ll need a partner to perform this next procedure. Refer to the circle and rectangle below. (If you or any of your volunteers wear glasses, leave them on.)

 

Left eye
1. Close your right eye.
2. Stare only at the rectangle with your left eye. Slowly move your head toward the computer screen until the circle disappears. Have your partner measure (in centimetres) the distance between the screen and your eye at this point.
3. Slowly move your head still closer to the computer until the circle reappears. Have your partner measure (in centimetres) the distance between the screen and your eye at this point.
4. The range of numbers (e.g. 15-22 cm) measures the blind spot in your left eye.

 

Right eye
1. Close your left eye.
2. Stare only at the circle with your right eye. Slowly move your head toward the computer screen until the rectangle disappears. Have your partner measure (in centimetres) the distance between the screen and your eye at this point.
3. Slowly move your head still closer to the computer until the rectangle reappears. Have your partner measure (in centimetres) the distance between the screen and your eye at this point.
4. The range of numbers measures the blind spot in your right eye.

 

1. Record the range of numbers for both your eyes.

Left eye = ______ cm to ______ cm

Right eye = ______ cm to ______ cm

 

2. Repeat these same procedures with several volunteers (include their data in your lab report). Do you notice a difference between individuals? Is there a difference in ranges between left and right eyes? Do you see a difference in ranges in volunteers of different ages? Interpret your results as best you can and describe what might be happening.

 

Experiment: Determining the distance of accommodation in each eye

When focusing on objects at different distances, the shape of the lens changes, a phenomenon known as accommodation. The lens is flattened when you’re looking at a distant object but curved when looking at a near object. The elasticity of the lens determines how well the eye can accommodate. Lens elasticity decreases with increasing age, resulting in the need for bifocals in older people. Children have more elastic lenses and so can sit close to an object (like a TV set) with the object still being in focus.

You’ll need a partner to perform this next procedure, which will test accommodation in your eyes.

1. Hold a pencil upright at arm’s length in front of whichever eye you’re testing.
2. Close the opposite eye.
3. Move the pencil toward your eye, keeping your eye focused on the end of the pencil.
4. Move the pencil as close to your eye as you can with it still being in focus (give your eye a little time to adjust). If the pencil is out of focus, your lens is no longer accommodating. Measure the distance (in centimeters) between the pencil and your eye.
5. Repeat this same procedure with your other eye.

 

3. Record the accommodation distance for both your eyes.

Left eye = _________ cm

Right eye = _________ cm

Calculate the mean distance of both eyes: Mean accommodation distance = _________ cm

 

4. Repeat these same procedures with several volunteers (include their data in your lab report). Do you notice a difference between individuals? Do you see a difference in mean accommodation distance between “young” volunteers and “older” volunteers? Interpret your results as best you can and describe what might be happening.

 

Experiment: Determining the location of sound by the ears

Just for fun, try out this online hearing test.

People locate the direction of sound according to how fast it’s detected by either or both ears. A difference in the hearing ability of the two ears can lead to a mistaken judgment about the direction of sound.
You’ll need a partner to perform this next procedure.
1. Sit in a chair with your eyes closed.
2. Your partner will rap a tuning fork against a rubber stopper and place the tuning fork at various locations around you (listed below; do in random order). Don’t move your head when this is being done. The idea is to locate the sound while keeping your head stationary.
3. Give the exact location of the sound in relation to your head. Your partner will record this information.

 

5. Record your perceptions when the sound is:

a. directly below and behind the head

b. directly behind the head

c. directly above the head

d. directly in front of the face

e. toward the left side of the head

f. toward the right side of the head

 

6. Is there an apparent difference in hearing between your two ears? Explain your results.

 

Experiment: Determining the density of touch receptors in the skin

You’ll need a partner to perform this next procedure.

1. Sit in a chair with your eyes closed.
2. Your partner will test your ability to discriminate between the points of two toothpicks held close together (or the two points of a hairpin) at various locations on your body (forearm, back of neck, index finger, and back of hand).
3. Have your partner hold the toothpicks close together on the given skin area, with both points simultaneously and GENTLY touching you.

 

7. Do you experience one touch sensation or two touch sensations for each region of the body tested?

a. forearm = _________

b. back of neck = _________

c. index finger = _________

d. back of hand = _________

 

8. On some parts of your body (e.g. the back), the toothpicks need to be farther apart before you can feel two distinct points. Record the shortest distance (in millimeters) between the toothpick points for a two-point discrimination.

a. forearm = _________mm

b. back of neck = _________mm

c. index finger = _________mm

d. back of hand = _________mm

Which of these areas contains the greatest density of touch receptors? Why is this useful?

 

Experiment: Determining the response of temperature change in the hand

Thermoreceptors in your skin respond to changes in temperature.

1. Use two bowls (or pans) large enough to immerse your hand into and one bowl (or pan) large enough to immerse both hands into simultaneously.
2. Fill one bowl with cold water, one with bathtub temperature water, and one with room temperature tap water. **The room temperature bowl must be large enough to fit both of your hands simultaneously.**
3. Arrange the bowls in front of you with the cold water on the left, the room temperature water in the middle, and the bathtub temperature water on the right.
4. Immerse your left hand in the cold water and your right hand in the bathtub temperature water for about 30 seconds.
5. Then place both hands in the bowl containing room temperature water.

 

9. What is the temperature sensation you feel in each of your hands after immersing them in the room temperature water? Explain your results.

 

Experiment: Determining the interaction of taste and smell
This experiment will demonstrate how smell and taste interact with one another to produce a particular flavor.

1. Close your eyes and randomly choose a Life Savor candy from a multi-flavored pack.
2. While keeping your eyes closed, unwrap the candy.
3. Keep your eyes closed and plug your nose. Put the candy in your mouth.
4. Before unplugging your nose, guess what flavour of candy you have.
5. Unplug your nose and guess the flavour again.
6. Take the candy out of your mouth to verify the flavour.
7. Repeat two more times. Make sure you rinse your mouth with water between trials.

 

10. Complete the following table.
Trial # Flavor while plugging nose Flavor after unplugging nose Actual flavor

 

11. Repeat this same procedure with several volunteers (include their data in your lab report). Fill out the above table for each of them. Do they experience the same phenomenon? Does smell affect the taste of the candy? What do you conclude about the effect of smell on your sense of taste?

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