BIOMEDICAL SCIENCE 100 LAB - SENSES I
PUT REQUESTED INFORMATION (NOTED IN RED) ON RESPONSE SHEET
  1. SOMATIC REFLEX (PATELLAR REFLEX) Patellar Reflex Diagram
    • Subject is seated on lab bench with legs hanging free or with knees crossed. Tap the patellar ligament sharply with the reflex hammer just below the knee. Test both knees.
    • Check the effect of simultaneous muscular activity by having the subject clasp his or her hands together and try to pull them apart while testing the reflex.

  2. AUTONOMIC REFLEX (PUPILLARY REFLEX) Pupillary Reflex Diagram | Pupillary Reflex Animation
    • Conduct the reflex testing in an area where the lighting is relatively dim.
    • Observe the size of the subject’s pupils.
    • Stand to the left of the subject. The subject should put his/her hand in the median plane (between the eyes).
    • Shine a flashlight into the subject’s left eye and immediately observe the sizes of both pupils again. Does shining a light into one eye only cause the other pupil to constrict?

  3. TACTILE LOCALIZATION Receptor Field Diagram
    • Subject’s eyes should be closed. Tester touches subject’s skin with a fine point marker.  Subject tries to touch the exact point with his or her own marker (of a different color). Measure the error of localization in millimeters. Repeat twice and take the average of all three trials.
    • Perform this procedure and record results for the skin areas listed below.
      skin area tested average error of localization (in mm.)
      fingertip ____________ mm.
      ventral forearm ____________ mm.

  4. THRESHOLD OF TWO-POINT DISCRIMINATION Two Point Discrimination Diagram
    • Using a caliper, test the ability of the subject to differentiate (with eyes closed) two distinct sensations when the skin is touched simultaneously at two points.
    • Begin with the caliper arms completely together. Gradually increase the distance between the arms until the subject reports that two points of contactcan be felt. The tester should occasionally touch the subject with one point only to prevent guessing.  Repeat twice and take the average of all three trials.
    • Perform this procedure and record results for the skin areas listed below.
      skin area tested threshold of two-point discrimination (in mm.)
      fingertip ________________ mm.
      back of hand ________________ mm.

  5. ADAPTATION OF TOUCH RECEPTORS Cutaneous Receptor Diagram
    • Subject’s eyes should be closed. Tester places a coin on the anterior surface of the subject’s forearm. Record the duration of sensation of one quarter: ___________sec.
    • After awareness of the sensation has been lost, stack three more coins atop the first one. Does the pressure sensations return? Record the duration of sensation of four quarters: ____________ sec.

  6. PROJECTION Ulnar Nerve Diagram
    • Subject immerses elbow in a bowl of ice water and keeps it there for two minutes.  After two minutes of immersion, report the type (tingling, numbness, etc.) and localization of sensation (elbow, etc.) to your partner.

  7. ADAPTATION OF TEMPERATURE RECEPTORS
    • Place one hand in ice water and the other in 45o C. water.  Keep both hands there for two minutes or until the cold hand begins to feel numb.
    • After two minutes, or when the cold hand begins to feel numb, place both hands simultaneously into room temperature water. Report the following information to the tester: What is the sensation in the left hand? What is the sensation in the right hand?

  8. RINNE TEST (CONDUCTION DEAFNESS) Ear Diagram
    • Tester strikes tuning fork (against hand or with mallet provided) and holds the handle of a vibrating tuning fork against the mastoid process of subject’s head. The tuning fork should be pointed back away from the ear. Under these conditions hearing is by “bone conduction”
    • When the sound can no longer be heard, the tester holds the tuning fork near the subject’s ear with the tips of the fork just outside the auditory canal.  Under these conditions hearing is by “air conduction.”
    • If the subject hears the fork again, air conduction is not impaired (positive Rinne test). If the subject does not hear the fork again, air conduction is impaired (negative Rinne test). Result of Rinne Test -  positive OR negative
    • Repeat Rinne test but “in reverse,” i.e., test air conduction before bone conduction.  If the subject hears the tone again by bone conduction after hearing by air conduction is lost, middle ear hearing impairment is confirmed.
    • Simulate conduction deafness by plugging one ear. Result of Rinne Test with one ear plugged - positive  OR  negative

  9. WEBER TEST (SENSORINEURAL DEAFNESS) Conductive Hearing Loss Audiogram
    • Strike a tuning fork and place the handle of the fork on the median line of the subject’s head. Is the perception of tone symmetric (equally loud in both ears) or lateralized (louder in one ear)?
    • If the tone is not perceived as equally loud in both ears, the subject has either: 1- sensorineural deafness in the ear in which the tone is perceived as weaker, or 2- conduction deafness in the ear in which the tone is perceived as stronger.
    • Simulate conduction deafness by plugging one ear. Result of Weber Test with one ear plugged - in which ear does the stimulation seem "louder?"

  10. THRESHOLDS OF HEARING (BASIC AUDIOMETRY) Selected Decibel Levels | Sensorineural Hearing Loss Audiogram
    • Subject is to wear headphones (red on the right) and inform tester when a tone is heard (audiometer should not be run on “Steady”).
    • Set the Frequency to 125 Hz.
    • Set the Intensity to 25 dB.
    • Use Ear Select to select an ear.
    • Press the Tone button.
      If the subject does not hear the tone, increase the Intensity to the next step and repeat Step e.
      If the subject does hear the tone, record the Intensity as the “Hearing Level” (Threshold of Hearing) for that ear and that frequency. Use O for right ear and X for left ear.
    • Increase the Frequency to the next one shown on the audiogram.
    • Return to Step c.
    • Continue until both ears have been tested at all frequencies shown on the sample audiogram.


    Threshold of Hearing (dB) Hearing Loss
    <= 25 dB (normal) (<=15 dB for children)
    26 - 40 dB mild
    41 - 55 dB moderate
    56 - 75 dB moderate to severe
    76 - 90 dB           severe
    > 90 dB profound
October 2010