Sensory System Human Anatomy and Physiology - ANAT 14 Lab Goals Observe many characteristics of our somatic and special senses. Activity descriptions noted in your lab manual are specified. Activities Patellar Reflex Eliciting the patellar reflex will demonstrate the least complex spinal reflex in our bodies while showing the separation of spinal and cerebral processing of sensory information. Have the subject sit on a table with the knees off the table and with the legs dangling. As the subject isometrically contracts the quadriceps muscles, palpate the patellar tendon (between the patella and tibial tuberosity). Have the subject relax all thigh muscles and tap the patellar tendon with the reflex hammer. Invoke the patellar reflex again with the subject s eyes closed. Have the subject compare the moment he/she is aware of being tapped to the time the leg starts swinging. Explain the cause for the difference. Visual Tests Distance Visual Acuity The distance visual acuity test will determine one s visual accuracy at a distance of twenty feet as compared to the visual accuracy of a person with normal visual. Have the subject stand 20 feet from the Snellen Eye Chart (the chart with a large E at the top). Remove any corrective lenses and cover the left eye. Using the right eye without squinting, the subject should read the letters of each line in order of decreasing size. The row of smallest legible letters with at least 50% accuracy indicates the distance visual acuity for that eye. The fraction associated with the smallest line read compares the subjects vision accuracy at 20 feet to a person with normal vision reading the same line. For example, a score of 20/40 indicates that the subject can read the 20/40 line accurately at twenty feet and a person with normal vision can read the same line accurately at forty feet. Repeat the test using the left eye and having the right eye covered.
If the subject normally wears corrective lenses, repeat the entire exercise while wearing the corrective lenses to determine the effectiveness of those lenses in distance visual acuity. Astigmatism Test This test will determine a presence of an astigmatism. Astigmatism is due to a non spherically shaped lens or eye. This leads to some light in the posterior chamber focusing either in front of or behind the retina. Remove any corrective lenses and cover the left eye. With the right eye, stare at the center of the astigmatism chart. With your peripheral vision, notice if any of the radiating lines appear equally sharp and dark. If they do all appear equal, an astigmatism is not present. If some lines are less sharp or lighter in color, then an astigmatism is present in that eye. Repeat the test using the left eye and having the right eye covered. Near Point of Vision This test will compare one s minimum reading distance to the normal minimum reading distance of people over a range of ages. With any corrective lenses removed, lean over the near point vision age chart (included at the end of this lab description) with a meter stick extending vertically from the chart to the side of your head. While focusing on the small print letters at the bottom of the chart, slowly lower your head towards the chart. As soon as the letters are no longer sharp, note the distance from the chart to your eyes. Using the chart, determine the normal age associated with this measured near point of vision distance. Color Deficiency (test and instructions provided in class) This test will determine if a red/green color deficiency is present. This test uses a series of plates filled with multi-colored dots. Specific patterns in these plates are only visible to those without a red/green color deficiency. Those with the deficiency are unable to see the patterns. Instructions and keys for interpreting results are included with the color deficiency plates. Blind Spot Observation This exercise will demonstrate the absence of photoreceptors at the optic disc by focusing an image at the optic disc. Using the graphic below, cover the left eye and focus the right eye on the + with the to the right of the +. Start with the image held at arm s
length from your right eye and slowly move the image towards your eye. With you peripheral vision, notice when the disappears. At this distance, the light reflecting off of the is focused on your optic disc where there are no photoreceptors. Consequently, you are not able to perceive the. Now, bring the image closer to your right eye and notice the reappear. Repeat this exercise while covering the right eye and focusing the left eye on the with the + to the left of the. + Peripheral Vision Test This test will demonstrate your ability to visualize fine detail using your peripheral vision. You will try to accurately identify two letters in your peripheral vision as they are slowly brought into the center of your field of vision. Instructions for conducting this test are provided with the testing apparatus. Auditory Tests Weber Test This test will demonstrate any unilateral deafness (difference in hearing sensitivity between the right and left ears). While holding on to the stem of a tuning fork, strike the fork and touch the end of the stem to the center of your forehead. This invokes hearing through bone conduction and bypasses conduction through the outer and middle ears. Note if the sound is louder in one ear than the other. Interpret this result using the table below.
Test Result Diagnosis Weber Equal loudness Normal hearing or equal hearing loss in both ears. Louder In Right Ear Conduction deafness in right ear or sensorineural deafness in left ear. Louder In Left Ear Conduction deafness in left ear or sensorineural deafness in right ear. Rinne Test This test will determine any deafness diagnosed with the Weber Test is due to conduction deafness or sensorineural deafness. While holding on to the stem of a tuning fork, strike the fork and touch the end of the stem to the right mastoid process. This tests hearing by bone conduction. Once the sound is no longer heard through bone conduction place the tuning fork near the right ear to test for hearing through air conduction. Interpret this result using the table below. If the diagnosis that conduction deafness may be present, repeat the exercise by starting with air conduction and then listening by bone conduction. Repeat the Rinne Test using the left ear. Test Result Diagnosis Rinne Can hear with air conduction after bone conduction. No conduction deafness in this ear. Cannot hear with air conduction after bone conduction. Conduction deafness may be present in this ear. Can hear with bone conduction after air conduction Conduction deafness present in this ear. Cannot hear with bone conduction after air conduction No conduction deafness present in this ear. Equilibrium Tests Balance Test This test will determine if the static equilibrium receptors of the vestibular apparatus are functioning properly. Have the subject stand perfectly still in front of a chalkboard without touching the chalkboard and let the arms hang at the sides. Mark the
outline of the subject s shoulders on the chalkboard. Have the subject close his/her eyes and notice any swaying motion at the shoulders. Dramatic swaying and possibly falling over suggests a malfunction in the static equilibrium receptors of the vestibular apparatus. Be in position to catch the subject incase he/she falls over. Barany Test This exercise will demonstrate the functioning of each pair of semicircular canals. Have the subject sit on a swivel chair with others in the immediate vicinity to prevent the subject from falling out of the chair and hitting the floor. Have the subject focus on a distant object with both eyes open while you spin the subject ten full rotations at a speed of 0.5 rotations per second (total of twenty seconds). At the completion of rotation, observe the direction of eye movement in the subject and interpret this result using the table below. Repeat the exercise with the subject s ear lying on the shoulder and again with the chin touching the chest. Eye Movement Laterally Vertically Rotationally Stimulated Semicircular Canal Lateral Canals Anterior Canals Posterior Canals Touch Tests These tests will demonstrate the size of one s perception fields on various regions of one s body. Smaller perceptions fields are due to a higher frequency of independent sensory receptors. Two Point Discrimination Threshold Gently touch the two points of a compass on the subject s skin starting with both points touching and slowly spreading them apart between each touch. Measure the distance between points when the subject is first able to distinguish two individual points. Perform this exercise on the following locations: Back of Hand Fingertip Back of Neck Forearm
Localization Perception Using a felt-tipped pen, make a single spot on the skin of a subject while the subject s eyes are closed. With a different colored pen and while keeping their eyes closed, have the subject mark on his/her skin where the first mark was felt. Measure the distance between the two markings. Perform this exercise on the following locations. Be sure to prevent pens from marking clothes, furniture, etc. Back of Hand Fingertip Forearm Temperature Perception This exercise will demonstrate the type of information temperature receptors are able to pass to the central nervous system (absolute or relative temperatures). Place your left hand in a beaker of warm water and your right hand a beaker of cold water for 30 seconds. Next, place both hands in beakers of room temperature water simultaneously. Note which hand perceives the water to be warm and which hand perceives the water to be cold.
80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 Human Anatomy and Physiology - ANAT 14 Near Point of Vision 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 Nearest Reading Distance (cm) Data used to develop this model were taken from Barry Tanowitz, Santa Barbara City College, http://www.biosbcc.net/tanowitz. Age With Normal Vision (yr)