Human Senses Lab

Purpose: To investigate the various human senses.

Materials:

Ø  Metric ruler

Ø  Paper

Ø  Pen

Ø  Cotton Swabs

Ø  Various Solutions

Part A: Vision

Blind Spot Determination

Because no photoreceptors are found in the area where the optic nerve is attached to the retina, this area is called the blind spot. To locate your blind spot, look at the symbols on the white strip of paper that looks like the strip below. Close your right eye and focus the left eye on the +. Hold the paper at arm’s length (about 60-70 cm away) directly in front of your face so that the + is directly in front of your open eye and the is to the outside of your face. Slowly move the page toward your eyes while looking at the +.

+

Answer the following questions on the answer sheet.

1.  Does the block dot disappear? This is known as the blind spot.

2.  Using a large ruler, have your partner measure the distance (in cm) between your left eye and the page. At what distance from your left eye do you reach your blind spot?

3.  Continue to move the page toward you. What happens to the black dot?

4.  Repeat the process using your right eye and focusing on the cross. Does the black dot disappear?

5.  At what distance from your right eye do your reach your blind spot?

6.  What happens to the black dot as you continue to move the paper strip towards you?

Dominant Eye Determination

Most individuals do not make use of both eyes. They depend more heavily on one eye – the dominant eye.

1.  Roll a sheet of paper into a tube approximately 4cm in diameter. Use paper in the scrap paper box.

2.  Hold the tube at arm’s length. Look through it with both eyes at some object across the room.

3.  With the tube held steady, close one eye then the other. Which eye still sees the object through the tube? This is your dominant eye. Is it on the same side as your dominant hand? Record your results on the lab data sheet.

Near Point of Vision

The distance from the eye to the nearest object that can be focused clearly is called the near point of vision.

1.  Place one hand over an eye and focus on a pin held vertically at arm’s length.

2.  Gradually bring the pin closer to your eye, focusing continually until the pin begins to blur.

3.  Have your partner measure the distance in centimeters from the eye to the pin at the point of blurring. This is your near point of vision. Measure to the nearest 0.5 centimeter.

4.  Repeat this process with the other eye and compare the two. Record your results on the answer sheet.

Afterimage

1.  Place an orange card on a sheet of white paper. Stare at the card for 30 seconds, and without moving your eyes, remove the card. You should continue to see a rectangular area where the card was. Have your partner time how long the after image stays visible to you.

2.  Repeat the process with the green card and have your partner time how long the after image stays visible to you.

Accommodation

Accommodation is the automatic adjustment of the eye for viewing objects at different distances. Muscles within the eye expand and contract to make this occur. As you get older, the amount of time needed to do this becomes longer.

  1. If you normally wear glasses, leave them on. Mark a large E on the back of your index finger. Stand 6.1 m (20 feet) from the Snellen chart. Hold up your index finger in front of you at arm’s length so the E on your finger appears beside the large E at the top of the chart. With both eyes open, look at the E on your finger and then look at the E on the chart. Do this several times. Answer questions 1 -3 on the lab data sheet.
  2. Alternate closing your left and right eye while looking at the E on the chart. What appears to happen to your finger? Answer question 4 on the lab data sheet.

Astigmatism

If the cornea or the lens of the eye is unequally curved, not all light rays will focus at the same point, and part of the visual field will be blurred. Stand in front of the astigmatism chart (about 8 feet away). Cover one eye with an index card and look at the center of the chart. All the radial lines appear to have the same darkness to the normal eye. However, the astigmatic eye will see some of the lines in sharp focus, making them appear darker than the lines that are out of focus. Repeat the test with the other eye and answer the questions on the lab data sheet.

Part B: Taste

Your tongue has taste buds for salty, sweet and sour foods in different areas. Follow the steps below to identify these areas.

  1. Obtain 2 Q-tips for each person. Use a 4-chamber tray and put about 25 drops of a different solution in each chamber. Label what is in each chamber.
  2. The test subject must sit with eyes closed at all times, with mouth open and tongue somewhat extended. They may NOT close their mouth or pull their tongue back in. The tester places one end of the moistened Q-tip swab on the subject’s tongue in this order:
  3. Tip of tongue
  4. Left and right sides of tongue
  5. Middle of tongue
  6. Back of tongue
  7. The test subject must indicate each time whether or not the taste is perceived. For a positive taste response, mark a Y on the appropriate area on the tongue indicated on your partner’s lab Data Sheet. For a negative response, mark an N on the appropriate area on the tongue. The test subject must rinse out their mouth before the next taste solution is tested.
  8. Repeat this for each of the 4 tastes, then switch roles and repeat all the tests. Throw away all used Q-tips when done.

Part C: Smell

Smell is the perception of particles or molecules in the air. These particles or molecules must be fat-soluble and water-soluble. Have your partner close their eyes for all the steps below.

1.  The test subject should place 8-10 drops of clove oil on a sterile swab and hold it under 1 nostril while closing the other. Inhale through the nose repeatedly and exhale through the mouth until the odor is no longer perceived.

2.  Record how many seconds it take before the test subject no longer smells cloves.

3.  The tester should very quickly hand the test subject a swab with 8-10 drops of peppermint oil. The test subject inhales the peppermint odor in the same say described above.

4.  Record your results on your lab data sheet.

5.  Change roles and repeat the test. Throw swabs away when done.

ALL NON-DISPOSABLE MATERIALS GO BACK IN THE BOX. PLEASE MAKE SURE ALL LIDS OF BOTTLES ARE ON TIGHT. GREAT JOB!!