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                                                      Ear Lab

Activity: Examining microscopic structures of the Cochlea

View the prepared microscope slide of the cochlea. Diagram under high power and label any identifiable
structures.
                     _____________ (              )




Activity 2: Acuity Test

Find a quiet area. Have your lab partner pack one ear with cotton and sit quietly with eyes closed. Obtain a
ticking clock or pocket watch and hold it very close to his/her unpacked ear. Then slowly move it away
from the ear until your partner signals that the ticking is no longer audible. Record the distance in inches
at which the ticking is inaudible.

Right Ear________________ Left Ear __________________

Is the threshold of audibility sharp or indefinite?



Activity 3: Sound localization

Ask your partner to close both eyes. Hold the pocket watch at an audible distance (about 6 inches) from
his/her ear, and move it to various locations (front, back, sides, and above the head). Have your partner
locate the position by pointing in each instance. Can the sound be localized equally well at all positions?
______________________________

If not, at what position(s) was the sound less easily located?
______________________________________________________________________

The ability to localize the source of a sound depends on two factors- the difference in the loudness of the
sound reaching each ear and the time of arrival of the sound at each ear. How does this information help to
explain your findings?
_____________________________________________________________________________________
Activity 4: Weber test to determine conductive and sensorineural deafness

                               Obtain a tuning fork and a rubber mallet. Strike the tuning fork with the
                               rubber mallet and place the handle of the tuning fork medially on your
                               partner’s head. Is the tone equally loud in both ears, or is it louder in one
                               ear?
                               _____________________________________________________________

                               If it is equally loud in both ears, you have equal hearing or equal loss of
                               hearing in both ears. If sensorineural deafness is present in one ear, the tone
                               will be heard in the unaffected ear, but not in the ear with sensorineural
                               deafness. If conduction deafness is present, the sound will be heard more
                               strongly in the ear in which there is hearing loss. Conduction deafness can
                               be simulated by plugging one ear with cotton to interfere with the
                               conduction of sound to the inner ear.


Activity 5: Rinne Test for comparing Bone and Air conduction hearing

                               1.     Strike the tuning fork, and place the handle on your partner’s
                               mastoid process.

                               2.      When your partner indicates that he or she can no longer hear the
                               sound, hold the still-vibrating prongs close to his/her auditory canal. If your
                               partner hears the fork again (by air conduction) when it is moved to that
                               position, hearing is not impaired. Record the test result as positive (+)

                               3.      Repeat the test, but this time test air conduction hearing first. After
                               the tone is no longer heard by air conduction, hold the handle of the tuning
                               fork on the bony mastoid process. If the subject hears the tone again by
                               bone conduction after hearing by air conduction is lost, there is some
                               conductive deafness and the result is recorded as negative (-).

                               4.      Repeat the sequence for the opposite ear.

                               Right Ear ____________________ Left Ear _________________________

                               Does the subject hear better by bone or by air conduction?
                               ________________________________


Activity 6: Balance Test

Have your partner walk a straight line, placing one foot directly in front of the other.

Is he or she able to walk without noticeable wobbling from side to side? ____________________

Did he or she experience any dizziness? ______________________

The ability to walk with balance and with dizziness, unless subject to rotational forces, indicates normal
function of the equilibrium apparatus.
Activity 7: Romberg Test

The Romberg test determines the soundness of the dorsal white column of the spinal cord, which transmits
impulses to the brain from the receptors involved with posture.

   1. Have your partner stand with his/her back to the blackboard.

   2. Draw one line parallel to each side of your partner’s body. He/She should stand erect, with feet
      together, eyes open and staring straight ahead for 2 minutes while you observe any movements.
      Did you see any gross swaying movements? ________________________________________

   3. Repeat the test. This time the subject’s eyes should be closed. Note and record the degree of side to
      side movement. ______________________________________________________________

   4. Repeat the test with the subject’s eyes first open and then closed. This time, however, the subject
      should be positioned with his/her left shoulder toward, but not touching, the board so that you may
      observe and record the degree of front to back swaying.
      _______________________________________________________________________________

       Do you think the equilibrium apparatus of the inner ear was operating equally well in all these
       tests? ______________________________________________________________________

       Why was the observed degree of swaying greater when the eyes were closed?
       _______________________________________________________________________________

       _______________________________________________________________________________

       What conclusions can you draw regarding the factors necessary for maintaining body equilibrium
       and balance?
       _______________________________________________________________________________

       _______________________________________________________________________________


Activity 8: Role of vision in maintaining equilibrium

To further demonstrate the role of vision in maintaining equilibrium, ask your lab partner to record
observations and act as a “spotter.” Stand erect, with your eyes open. Raise your left foot approx. 1 ft off
the floor, and hold it there for one minute.

Record the observations
_____________________________________________________________________________________

_____________________________________________________________________________________

Rest for 1 or 2 minutes, and then repeat the experiment with the same foot raised, but with your eyes
closed.

Record the observations

				
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