BSPD211 Special Senses Practical - Olfaction, Vision, Hearing PDF

SURNAME: ___________________________________________ BSPD211 STUDENT #: __________________________________________ SPECIAL SENSES: Olfaction, Vision, Hearing and Balance OLFACTORY DISCRIMINATION Receptors for the sense of smell are loc...

SURNAME: ___________________________________________ BSPD211 STUDENT #: __________________________________________ SPECIAL SENSES: Olfaction, Vision, Hearing and Balance OLFACTORY DISCRIMINATION Receptors for the sense of smell are located high in the interior of the nose between the median septum and in the area of the superior turbinate (olfactory cleft). Olfactory nerves pass superiorly through the cribiform plate of the ethmoid, which is lateral and inferior to the crista galli, and from there pass to the olfactory bulbs. The nasal passages are lined with mucous membranes and cilia, which moisten and warm the air during breathing. When someone has a cold, the membranes tend to swell and secrete excessive mucus and therefore impair the sense of smell. The following exercises are designed to test your ability to discriminate different scents. The sense of smell is complex, and the ability to determine scent varies with the individual. Test your ability and compare it with that of your friend. Materials: Samples of vanilla extract, garlic, cloves, vinegar, coffee, fabric softener PROCEDURE 1. Groups of 2 are suggested for this exercise. 2. Select several different samples (see materials for examples). 3. You are to smell each with your eyes closed and identify it. 4. Keep a list of the samples and your responses. SAMPLE RESPONSE SAMPLE RESPONSE (Can identify or not) (Can identify or not) 1 VISION A: Accommodation 1. To measure the near point of vision, place the end of a ruler under one eye and extend it. Please be careful when doing this. 2. Holding an object (pencil, pen, etc), gradually bring the object toward the eye. 3. Record the distance at which the object first appears blurred or doubled (i.e. no longer in focus) Near point of vision for right eye: __________cm 4. Repeat on the other eye Near point of vision for left eye: ___________cm Answer the following questions: 1. Define accommodation: ___________________________________________________________________________________________ ___________________________________________________________________________________________ 2. Which two structures of the eye are responsible for accommodation? __________________________________________________________________________________________ B: Visual Acuity The most important part of testing any organ, is the test of how well the organ works. So, when it comes to the eye, we need to assess how well the eye sees. This function is known as the visual acuity, or sharpness of vision. What is the Snellen chart? The test is based on what a person with normal vision can read or identify at a distance of 20 feet (6m). Why 20 feet? Because the light rays emanating from an object at this distance are parallel, and do not require refraction, or bending by the eye, in order to come to a focus on the retina - testing at 20 feet is the equivalent to testing at any greater distance, or infinity. Each line on the chart has a designated number, ranging from 200 for the largest letter on the top line, to 20, or even 10, for the lower lines. Although the 20 line is accepted as the line of normal vision, it happens that some people have super vision, and this is why numbers lower than 20 are used. The patient reads the chart as far down as possible and should they reach the 20 line, we say that that person has 20/20 vision. Should the eye only see as far down as the 40 line, [20/40], this means that in order for that eye to see the letter 2 that the normal eye saw at 20 feet, the letter will have to be twice as large. So this vision is less acute. Similarly, 20/200 vision, means that this eye sees at 20 feet what the normal eye can see at 200 feet. Activity: Watch the video that explains the Visual Acuity Test - https://youtu.be/26A0ioefOt0. Answer the following questions: A visual acuity test was conducted. The following results were obtained: Right eye: 20/50 Left eye: 20/30 Overall (With both eyes open): 20/25 1. Looking at the overall visual acuity, explain what the numbers mean: Numerator:________________________________________________________________________________ Denominator:______________________________________________________________________________ 2. Does the person have emmetropia (normal), hyperopia, or myopia? __________________________________ 3. What type of lens can be used to correct the visual deficiency? _____________________________________ 4. If your vision is 20/10, you have (circle the correct answer): a) myopia. b) hyperopia. c) emmetropia. d) above average visual acuity. C: Astigmatism vision test Activity: Stare at the center of the object: If one set of the lines appears darker than the other, you may have astigmatism. Contact your eye specialist to have a comprehensive evaluation. 3 D: Color vision Colour blindness is the inability to distinguish between some colours that others can. It is most often seen as a genetic trait, but can result from damage to the eye, nerves or brain. Cones are less sensitive than rods to light, but provide colour vision and greater visual acuity. During the day, therefore, the high light intensity bleaches out the rods, and colour vision with high acuity is provided by the cones. There appears to be three types of cones: blue cones, green cones and red cones. Activity: Watch the following video that shows what it’s like to be colour blind : https://youtu.be/CwnnXtUMv0g Take the online Colour blindness test - https://www.mobilefish.com/services/ishihara_test/ishihara_test.php - to determine whether you are colour blind or not. HEARING AND EQUILIBRIUM The ear is composed of the external, middle and inner ear. The external structures act to gather sound waves and to direct them inward to the eardrum of the middle ear. The ossicles in the middle ear transmit and amplify the sound waves to the inner ear where the hearing receptors are located. As they are stimulated, these receptors initiate nerve impulses to pass over the vestibulocochlear nerve into the auditory cortex of the brain, where the impulses are interpreted, and the sensation of hearing is created. A: Deafness Activity: Watch the following video that showing Rinne’s (conduction deafness) and Weber’s (sensorineural deafness and conduction deafness) test. https://youtu.be/LhcW0OAYrqk Answer the following questions: 1. What was the outcome when one of your ears were plugged with the finger? ________________________________________________________________________________________________ 2. Where should the sound be loudest? _______________________________________________________________________________________________ 4 B: Equilibrium - Vestibular Nystagmus Activity: Watch the following video on rotational nystagmus and answer the questions that follow: https://www.youtube.com/watch?v=BgtsFYmNF4w Answer the following questions: 1. Describe the eye movement: _______________________________________________________________________________________________ _______________________________________________________________________________________________ 2. The organ that detects equilibrium is called the ____________________________________________________. 3. The structures sensitive to angular/rotational acceleration in the three planes are the ____________________________________________________________. 4. The structures sensitive to linear acceleration are the __________________________________ (horizontal) and ___________________________________ (vertical). 5