week 5 bio labbb

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Chamberlain College of Nursing *

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251

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Mechanical Engineering

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Feb 20, 2024

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Week 5 Lab Instructions Special Senses – Eye Dissection and Psychophysics Activity Deliverable Points Part A Eye Dissection 10 Part B Special Senses Experiment 20 All Lab Deliverables Complete Parts A and B 30 References: 1. Saladin Anatomy & Physiology: The Unity of Form and Function Part A Step 1: Read the Entire Laboratory Packet 1.0– Read through the laboratory packet – SEE ATTACHED SHEETS Part A Step 2: Eye Dissection and Anatomical Identification BACKGROUND: VISION The human eye is an intricate special sense organ. It functions to take in light from the external environment and convert that light into an electrical signal. The electrical signal is then transmitted to the occipital lobe of the brain where it is converted into a thought interpretation of the detailed image being seen. The eye can be divided into two sections: the refractive section that is responsible for bending the light to focus it on the back of the eye and the photoreceptive system that is responsible for the conversion of the light into a nervous signal. BIOS252 Week 6 Lab Instructions (B) Page 1 of 24

OUTCOMES: In this lab, you will be asked to look at and describe the cellular and functional components of the nervous system. You will be able to identify the special senses structures and their neurologic functions. This lab will be covering the following course outcome: CO2: Given an illustration of the nervous system, analyze its structure and function. MATERIALS: Obtain needed equipment and supplies to be set up at your laboratory station  gloves  laboratory coat  dissection tray  blunt probes  scissors  sheep eye  forceps  scalpel (small handle) and #10 blade BIOS252 Week 6 Lab Instructions (B) Page 2 of 24

 psychophysics sheet with x and o (see page 10 of packet)  ruler PREPARATION:  Read your lab in its entirety before coming to class.  Clear your workstation of all unnecessary materials. Book bags and or purses should be hung on hooks or places at the front of class. Make sure all other unnecessary materials (coats, drink containers, unused textbooks, etc.) are all stored and placed in a safe area out of the way.  Obtain all materials listed above.  Familiarize yourself with your lab materials.  Follow the directions of the packet and as presented by your instructor to learn the surface features of the central nervous system.  Be aware of the instructions for documenting your lab work. You will be performing the lab by yourself or with your group partners. Make sure to select who will be performing the experiments and who will record the results. ACTIVITY: Identify the following parts of the eye during your dissection A. Optic nerve B. Sclera C. Iris D. Retina E. Lens F. Pupil G. Vitreous humor H. Aqueous humor I. Choroid J. Tapetum K. Optic disc L. Ciliary Body M. Hyaloid Fossa N. Zonula Ciliarilis O. Area centralis / fovea P. Blind Spot a) Identify the structures numbered: a. 1_____cornea_________ b. 2______sclera________ c. 3 ______optic nerve________ d. 4____iris__________ e. 5_______pupil_______ f. 10____retina__________ g. 11______lens________ BIOS252 Week 6 Lab Instructions (B) Page 3 of 24

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b) Dispose of eye as directed by your instructor. c) Clean laboratory instruments and station as directed by your instructor W6 - Eye Dissection Procedure (If the below instructions are too difficult to follow, refer to the document posted on canvas titled “Eye Dissection Procedure-BIO252-WK5-LAB” 1. Refer to the diagram of the eye as a general reference as you observe and identify external and internal structures and use the pages from the lab workbook: pp 359 - 369 2. Observe the outer structure of the eye. Identify the following: optic nerve, sclera, cornea, extra-ocular muscles 3. Trim away excess tissue surrounding the eyeball on the sclera 4. Hold the eyeball gently with your thumb and forefinger at the cornea and near the optic nerve 5. Begin a cross-section of the eye by making an incision slightly behind the middle of the eyeball through the sclera. Do not cut deep into the eyeball or squeeze it too tightly, so as not to damage the interior structures. You should begin the incision with a scalpel and complete cutting around the eye in the frontal plane with small iris scissors, or you may use a scalpel for the entire cut (not recommended). If some of the vitreous humor begins to ooze out of the eyeball as you cut through the sclera, let it come out slowly. BIOS252 Week 6 Lab Instructions (B) Page 4 of 24

6. Once you have made the incision around the eyeball, separate the eye into halves (posterior and anterior). Let the vitreous humor – the gelatinous transparent material found inside the eye behind the lens – and any associated structures slowly slide out of the eye. You may need to tease the vitreous humor gently away from the lining of the eye. It may be easier if you place the posterior portion of the eye in a petri dish or a large weigh boat filled with water and complete this through a dissecting microscope. 7. Look at the front portion of the eyeball. The lens may still be suspended in the middle of the pupil. Tip the front portion over to let the lens and associated structures fall out. Again, depending upon the viscosity of the vitreous humor, you may need to tease the material loose from the inside of the eye. 8. Observe the vitreous body, lens and associated structures. The hyaloids fossa is an indentation in the center of the vitreous body that supports the lens. Surrounding the hyaloid fossa is the zonula ciliaris, made up of the suspensory ligaments that suspend the lens and stretch it to focus on near or far objects. You will also notice dark lines around the hyaloid fossa. These lines are pigment from the iris. 9. Pick up the lens with a pair of forceps. Pat it dry with a paper towel. NOTE: You may want to place the lens over some printed text on the paper and observe its ability to magnify. This works best if the lens dries for a period of time – however if the lens has been ‘fixed’ for a long period of time then it becomes opaque. 10. Turn the front half of the eyeball over so that you are looking at the cornea. Cut the front of the eye around the outside of the cornea (where the cornea meets the sclera) to remove the cornea. This cut works best if you make the initial cut with a scalpel but then uses iris scissors to finish the incision. 11. Place the cornea on your dissecting tray and cut it in half to observe its thickness. 12. Insert the forceps through the opening created and carefully separate the edge of the iris from the inner surface of the eye. You may be able to remove the iris intact. 13. Pick up the back half of the eyeball and observe the structures on the inside. Identify the retina, which contains the receptors. Follow the mass of axons to their convergence point at the back of the eye, where the optic nerve begins. This is called the blind spot. 14. Look at the front of the retina to observe the area centralis (fovea) where the greatest density of receptors is located. Note that the fovea does not contain any blood vessels that would disrupt the high acuity found in the fovea. 15. Turn the back half of the eyeball over and observe the optic nerve on the outside of the eye. Pinch the nerve with your forceps to see the separate fibers of the nerve. 16. Look at the interior surface of the back portion of the eyeball again. Move the retina gently so that you can see the dark, metallic-looking tissue at the back of the eye. This is the choroid, a thin layer that lies BIOS252 Week 6 Lab Instructions (B) Page 5 of 24

between the retina and the sclera. The portion of the choroid that appears iridescent blue/green with shades of yellow is called the tapetum 17. Gently lift the retina from the choroid – dissect the point of contact of the retina from the optic disc – transfer the retina into a weigh boat with isotonic saline 18. Use a dissecting microscope to flatten the retina and then observe the pattern of fibers and blood vessels on the retina. Try to determine the location of the area centralis (visual streak for sheep) that would be their equivalent to the human fovea. 19. Dispose of the eye according to the instructions of your instructor. 20. Clean the dissecting tray and instruments in an approved fashion OBSERVATION REPORT: All members of the group will need to turn in individual copies of the assignment sheet – you may work on finding the answers as a group (either in your textbook or using internet resources) W6 Functional Eye Components Worksheet (10 pts) BIOS252 Week 6 Lab Instructions (B) Page 6 of 24

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Name and describe the two structures that help focus the light rays on the retina (1 pt): The cornea and the lens. Cornea - The cornea is the transparent outer layer of the eye that acts like a protective window. It's the first structure that light encounters when it enters the eye. The curved shape of the cornea bends and refracts incoming light, helping to focus it onto the retina at the back of the eye. Lens - Behind the iris is the lens, a flexible and transparent structure. Its role is to fine-tune the focusing of light onto the retina. The lens helps to focus light rays on the retina through a process known as accommodation. Accommodation involves changes in the shape of the lens to adjust its focal length, allowing the eye to focus on objects at different distances. Name the structures that make up the wall of the eyeball (three of them) (1 pt): The sclera, choroid, and retina are the three layers of the eyeball wall. Describe the location and functions of the following parts of the eye – be prepared to show your instructor where they are located. (8 pts) Optic nerve Send visual messages to brain to help you see. Back of each eye that connects directly to your brain. Sclera Supporting wall of the eyeball. Help maintain eye shape and protects from injury. Iris Colored part of the eye that regulates light entering the eyes. Behind anterior chamber, a space located filled with aquous humor. Retina thin layer of tissue that lines the back of the eye on the inside. Located near optic nerve. receive light that the lens has focused, convert the light into neural signals, and send these signals on to the brain for visual recognition. Lens curved disk that sits behind the iris and in front of the vitreous of the eye. It is the part of the eye that focuses light and images from the outer world, bending them onto the retina. Pupil The pupil is the opening in the center of the iris (the structure that gives our eyes their color). The function of the pupil is to allow light to enter the eye so it can be focused on the retina to begin the process of sight. Vitreous body Located in posterior segment and fills the vitreous chamber. The vitreous humor provides nutrients to your eye and helps your eye keep its shape. It sticks to your retina at the back of your eye and lets light in. BIOS252 Week 6 Lab Instructions (B) Page 7 of 24

Aqueous humor Your eyes continuously make aqueous humor, the clear fluid in the front part of your eye. The aqueous humor keeps your eye inflated and provides nourishment. The vitreous humor, also called vitreous fluid, is a clear gel-like substance that's located in your eye. Choroid a dense network of blood vessels and pigmented stroma between the retina and the sclera. The choroid supplies nutrition to the posterior layers of the retina. The choroid is the middle layer of tissue in the wall of the eye. It's found between the sclera (the whites of the eyes) and the retina (the light-sensitive tissue in the back of the eye). Optic disc represents the beginning of the optic nerve (second cranial nerve) and is the point where the axons of retinal ganglion cells come together. The optic disc is also the entry point for the major blood vessels that supply the retina. The optic disc is an elevation on the medial aspect of the retina where the sensory fibers and retinal vessels pass through the eyeball. Ciliary Body The ciliary muscle is in charge of changing the shape of the lens, while the ciliary processes participate in the production of the fluid in the eye also known as the aqueous humor. The ciliary body is attached to the lens by the collection of tiny fibrous cords known as the zonular fibers. Macula lutea The macula is the part of your eye that processes what you see directly in front of you (your central vision). It's part of your retina and is key to your vision. The macula is the round area at the center of your retina, at the back of your eyeball. Area centralis / fovea The fovea centralis is located in the center of the macula lutea, a small, flat spot located exactly in the center of the posterior portion of the retina. As the fovea is responsible for high-acuity vision it is densely saturated with cone photoreceptors. Blind Spot Your retina is made up of light-sensitive cells which send messages to your brain about what you see. Everyone has a spot in their retina where the optic nerve connects. In this area there are no light-sensitive cells so this part of your retina can't see. We call this the blind spot. BIOS252 Week 6 Lab Instructions (B) Page 8 of 24

Part B: The Special Senses BACKGROUND: Special senses are specialized sensory nerves that require a specialized receptor cell instead of a generalized nerve ending. We have already looked intensely at one of our special senses, let’s take a look at the others – taste (gustation), smell (olfaction), vision, hearing, and equilibrium. OUTCOMES: In this lab, you will be asked to look at and describe the cellular and functional components of the nervous system. You will be able to identify surface anatomical structures on the brain. This lab will be covering the following course outcome: CO2: Given an illustration of the nervous system, analyze its structure and function. MATERIALS: Obtain needed equipment and supplies to be set up at your laboratory station  Peppermint oil, 7 mL  Clove oil, 7 mL  Straight pins (3)  Snellen eye chart  Astigmatism chart  Packs of 2 sterile cotton applicators (3)  Card test tube rack  Plastic test tube  Disposable penlight  Measuring tape  Resealable plastic bag (2)  Tuning fork  Ruler  Stopwatch  Scissors  Pen or pencil  Drinking water  Salt packet  Sugar packet  Paper towel PREPARATION:  Read your lab in its entirety before coming to class.  Clear your workstation of all unnecessary materials. Book bags and or purses should be hung on hooks or places at the front of class. Make sure all other unnecessary materials (coats, drink containers, unused textbooks, etc.) are all stored and placed in a safe area out of the way.  Obtain all materials listed above.  Familiarize yourself with your lab materials.  Follow the directions of the packet and as presented by your instructor to learn the surface features of the central nervous system.  Be aware of the instructions for documenting your lab work. You will be performing the lab by yourself or with your group partners. Make sure to select who will be performing the experiments and who will record the results. BIOS252 Week 6 Lab Instructions (B) Page 9 of 24

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ACTIVITY: SMELL-OLFACTORY FATIGUE PUPIL LIGHT REFLEXES- Video for how to perform pupillary light reflex test- https://www.youtube.com/watch?v=R4e7vcvDgHw 1. Have the subject sit with their eyes closed for 1-2 minutes. Gently cover the subjects right eye with their own hand 2. From the lateral, move the penlight across the front of the patient until shining the light directly into the subject’s left eye 3. Observe the pupil size and record your results in the Observation Report 4. Repeat steps 1-3 with the subject’s left eye covered and right eye exposed and record your results in your Observation Report BIOS252 Week 6 Lab Instructions (B) Page 10 of 24

Pupillary light reflex  Definition : constriction of the pupils in response to light  Types o Direct pupillary reflex: constriction of the pupil in response to ipsilateral light stimulation o Indirect pupillary reflex (consensual pupillary reflex): constriction of the pupil in response to illumination of the contralateral eye. BLIND SPOT TEST Video showing how to perform blind spot test: https://www.youtube.com/watch?v=MMgff7jr_WA BACKGROUND: The optic disc is the place where the optic nerve (along with the optic blood vessels) leaves the back of the eye. There are no photoreceptor cells present here so it is essentially a blind spot in your vision. You do not notice this blind spot because the visual cortex of the occipital lobe takes the information from the photoreceptors cells surrounding this structure and use that information to “guess” and fill in that spot. In this experiment, we will demonstrate this. Follow the directions of the packet and as presented by your instructor to set up the demonstration experiment blind spot localization and size. BIOS252 Week 6 Lab Instructions (B) Page 11 of 24

ACTIVITY: a) Conduct the visual psychophysics experiment on determination of blind spot (optic disc) as explained in the attached laboratory directions (see attached form at the end of the laboratory) b) Have all members of the laboratory group determine their distances to the blind spot. c) Each member of the team individually enters their data and answer the question on the enclosed worksheet (page 7 of laboratory instructions) d) Submit the Blind Spot Determination Worksheet to your instructor via uploading into Canvas 1. Detach the following sheet with the circle and the x. Hold the sheet directly in front of you at arm’s length. Close your LEFT eye. Keep you right eye open and focus on the circle. You must fixate on the circle and not move your eye or gaze around. SLOWLY move the sheet towards you. When the BIOS252 Week 6 Lab Instructions (B) Page 12 of 24

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X disappears then its image is on your blind spot. Note: if you move the sheet too quickly then you will miss the crossing as your brain is always filling in the details of the blind spot with surface features from the surrounding retina. 2. Have a lab partner measure the distance that the sheet is from your face when the X disappears. Check out the size of the blind spot by slowly rotating the sheet while the X is in the blind spot. How far do you have to rotate the sheet to see the X again? Blind spot distance for right eye (cm):_______________________ 3. You will now repeat the experiment for the other eye: Close your right eye. Keep your left eye open and focus on the X. Slowly move the sheet towards you until the circle disappears. Rotate to check the accuracy of the blind spot and measure the distance. Blind spot distance for left eye (cm):______________________ Blind Spot Testing Sheet BIOS252 Week 6 Lab Instructions (B) Page 13 of 24

BIOS252 Week 6 Lab Instructions (B) Page 14 of 24

NEAR POINT ACTIVITY: Video showing how to perform https://www.youtube.com/watch? v=rwFKPJmFFtU 1. Have the subject place the “0” end of the ruler near the cheek of the left eye 2. Place a hand gently over the right eye covering the eye 3. Have the subject hold a straight pin with the point upward and slowly move it along the ruler closer to the eye 4. When the subject can no longer focus on the pin, make note of the distance away from the eye the pin is along the ruler and record the value in the Observation Report 5. Repeat steps 1-4 using the right eye while covering the left eye and record your results in the Observation Report Snellen Eye Chart: Video showing how to perform https://www.youtube.com/watch?v=kcULvDBJOVs 1. Go to the Snellen Eye Chart hanging on the classroom wall 2. Have the subject stand on the line marked on the floor 20 feet away from the chart. If corrective lenses are worn, have subject remove the corrective lenses 3. Have subject place their right hand over their right eye, covering the eye 4. Have the observer point to a line on the chart and have the subject call out the printed letters in that line. Have the subject continue reading the letters until they can no longer make out the letters 5. Note the visual value that is shown on the last line the subject could read all the letters correctly and record this value on the Observation Report 6. Repeat steps 1-5 using the left eye and record your results on the Observation Report ASTIGMATISM CHART: Video showing how to perform https://www.youtube.com/watch? v=DpSB6TNLKxg 1. Go to the Astigmatism Test Chart hanging on the classroom wall 2. Have the subject stand on a mark 8-10 feet from the chart. If corrective lenses are worn, have the subject remove the lenses before performing the test 3. Have the subject gently cover the entire right eye. Using the left eye, report if the subject sees any thick/dark lines on the chart and record your observations in the Observation Report 4. Repeat steps 1-3 while covering the left eye and using the right eye. Record your observations in the Observation Report BONE CONDUCTION: Video showing how to perform the Weber and Rinne Test: https://www.youtube.com/watch?v=FgF91K7dU8Y CAUTION – this test should not be used for diagnosis of a hearing impairment. If you believe you may have a hearing impairment, seek medical professional help for additional testing. 1. Have the subject plug both ears with their index fingers of each hand 2. The observer should hold the tuning fork by the handle and strike the prongs against the heel of your hands causing the tuning fork to resonate. Once resonating, place the handle of the tuning fork on the top of the subject’s head in between their ears 3. Move the tuning fork about 1 foot above the subject’s head then return to their head BIOS252 Week 6 Lab Instructions (B) Page 15 of 24

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4. Record if the subject could hear the tuning fork when it was moved away from the head and when it was returned and record your results in the Observation Report 5. Repeat steps 1-4 this time placing the tuning fork on the patient’s right temple instead of on top of their head and record your results in the Observation Report RINNE TEST CAUTION – this test should not be used for diagnosis of a hearing impairment. If you believe you may have a hearing impairment, seek medical professional help for additional testing. 1. Having the subject sitting in front of the observer, have the observer strike the tuning fork on the palm of their hand while holding the handle. Place the handle of the vibrating tuning fork on the mastoid process behind the right ear 2. When the subject can no longer hear the tuning fork, remove the tuning fork from the mastoid and place it next to the ear. Be careful not to bump into the ear and do not restrike the tuning fork 3. Ask the subject if they can hear the tuning fork 4. If the subject can again hear the tuning fork, hearing is considered unimpaired 5. Record your results in the Observation Report 6. Repeat steps 1-5 using the patient’s left ear and record your results in the Observation Report STANDING EQUILIBRIUM TESTS CAUTION – make sure subject is standing on an even surface in an area free of obstructions should the subject begin to fall. Make sure the observer stands nearby and is prepared to catch the subject should the begin to fall. 1. Have the subject stand still with their heels and feet side by side along with their arms crossed over their chest with their eyes open for up to 30 seconds. Record your results in the Observation Report 2. Have the subject stand still with their heels and feet side by side along with their arms crossed over their chest with their eyes closed for up to 30 seconds. Record your results in the Observation Report 3. Have the subject stand still with one foot directly in front of the other ( heel to toe position ) along with their arms crossed over their chest with their eyes open for up to 30 seconds. Record your results in the Observation Report 4. Have the subject stand still with one foot directly in front of the other ( heel to toe position ) along with their arms crossed over their chest with their eyes closed for up to 30 seconds. Record your results in the Observation Report 5. Have the subject stand still on one leg along with their arms crossed over their chest with their eyes open for up to 30 seconds. Record your results in the Observation Report 6. Have the subject stand still on one leg along with their arms crossed over their chest with their eyes closed for up to 30 seconds. Record your results in the Observation Report Clean up and dispose of all throw away materials used in the lab. Return all tools used for the lab to the designated area as described by your professor. BIOS252 Week 6 Lab Instructions (B) Page 16 of 24

OBSERVATION REPORT: (6 pts for filling in all tables) FRAGRANCE RIGHT NOSTRIL FATIGUE (in seconds) LEFT NOSTRIL FATIGUE (in seconds) Peppermint Oil Clove Oil FOOD IDENTIFIED? (Y/N) Salt Sugar Left eye Right eye Distance when point disappeared (cm) Left eye Right eye Visual acuity Visual acuity (with corrective lenses) BIOS252 Week 6 Lab Instructions (B) Page 17 of 24 PUPIL LIGHT REFLEX LEFT EYE RIGHT EYE Direct Indirect Left Eye Right Eye Near point (cm) Left eye Right eye Astigmatism present? (Y/N)

Yes No Sound heard with fork on head? Sound heard when fork moved away? Sound heard when fork returned? Sound heard with fork on temple? Sound intensity same in both ears? Test Position Time (sec) Feet together, eyes open Feet together, eyes closed Heel to toe, eyes open Heel to toe, eyes closed One leg, eyes open One leg, eyes closed Blind spot Determination Worksheet: Answer the following questions and return to your instructor: a. Why doesn’t the circle and X disappear at the same time when you close one eye? (1 pt) When you close one eye, you're effectively blocking visual input from that eye. The circle and X you're referring to are likely part of a simple experiment to demonstrate the blind spot. Each eye has its own blind spot where the optic nerve exits the retina, and this area lacks photoreceptor cells (rods and cones) responsible for detecting light. When you close one eye, the other eye's vision is unaffected, and you can still see the circle or X. If you position the circle or X in such a way that it falls onto the blind spot of the open eye, it will disappear from your visual perception. b. Is the distance of the sheet to the blind spot for the left eye and right eye the same? Why or Why not? (1 pt) The distance of the sheet to the blind spot might not be the same for the left and right eyes. The blind spot is the point on the retina where the optic nerve exits the eye, and its location can slightly vary between individuals and between the left and right eyes of the same person. As a result, the distance from your eyes to the blind spot may not be exactly the same for both eyes. BIOS252 Week 6 Lab Instructions (B) Page 18 of 24 Side Rinne Test Results Left ear Right ear

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c. Why do you have to close the other eye to have the blind spot experiment work? (1 pt) You have to close the other eye to make the blind spot experiment work because each eye's blind spot is located in a slightly different area of the visual field. When both eyes are open, the brain combines the information from both eyes to fill in the missing information from each eye's blind spot, effectively compensating for the lack of visual input in those areas. If you close one eye, the brain no longer has the information from the other eye to fill in the blind spot of the closed eye, causing the circle or X to disappear when it falls within the blind spot. d. Why does the x or circle reappear when you rotate the testing sheet (especially considering that you keep the sheet at the same distance as your blind spot)? (1 pt) The circle or X reappears when you rotate the testing sheet because the blind spot experiment takes advantage of the brain's ability to fill in missing visual information. When you rotate the sheet, you're changing the orientation of the image falling onto the retina. This change in orientation might cause the circle or X to fall outside the blind spot area of the retina, allowing the surrounding visual information to be processed by the brain and making the circle or X visible again. The distance of the sheet from your eyes is still important, but the change in orientation also plays a role in making the image visible. Special Senses Questions: 1.) What is the name of the skull bone that is covered by the olfactory membrane? (1 pt) Ethmoid bone. 2.) Starting with the olfactory membrane, name the cells that must be stimulated to send the sense of smell to the cerebrum. (1 pt) The olfactory epithelium is made up of ciliary receptor cells. these cells when stimulated by odor particles send the stimulation to the olfactory lobe that has glomeruli cells that connects posteriorly with mitral cells. BIOS252 Week 6 Lab Instructions (B) Page 19 of 24

3.) Which lobe of the cerebrum is responsible for the sense of smell? (1 pt) Frontal lobe 4.) Which of the papilla contain taste buds? What is the name of the special sensory receptor cell that gives you taste? (1 pt) Taste buds appear at the apex of fungiform papillae on the anterior tongue and along trench walls of foliate and circumvallate papillae on the posterior tongue. Taste buds are also found on the soft palate and the epiglottis. 5.) Which cranial nerve(s) are responsible for taste? (1 pt) the facial (VII), glossopharyngeal (IX), and vagus (X) 6.) What is the order that cells are stimulated in the retina when hit with light? (1 pt) As light falls on the retina, it first activates receptor cells known as rods and cones. The activation of these cells then spreads to the bipolar cells and then to the ganglion cells, which gather together and converge, like the strands of a rope, forming the optic nerve. The order that cells are stimulated in the retina when hit with light is Photoreceptor Cells (rods and cones) → Bipolar Cells → Ganglion Cells. BIOS252 Week 6 Lab Instructions (B) Page 20 of 24

7.) What causes nearsightedness? Farsightedness? (1 pt) Curvature of the lens – If the lens is too steeply curved in relation to the length of the eye and the curvature of the cornea, this causes nearsightedness. If the lens is too flat, the result is farsightedness. 8.) What does it mean to have an astigmatism? (1 pt) Astigmatism occurs when either the front surface of the eye (cornea) or the lens inside the eye has mismatched curves. Instead of having one curve like a round ball, the surface is egg-shaped. This causes blurred vision at all distances. 9.) Which nerve(s) is responsible for balance? (1 pt) vestibulocochlear nerve (VIII) 10.)What is the order of cell stimulation/activation to generate a sense of hearing? (Start with the tympanic membrane) (1 pt) BIOS252 Week 6 Lab Instructions (B) Page 21 of 24

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Tympanic Membrane (eardrum) → Auditory Ossicles (Malleus, Incus, Stapes) → Oval Window → Fluid in the Cochlea → Hair Cells in the Organ of Corti → Auditory Nerve (Cranial Nerve VIII) → Brainstem and Auditory Cortex. Submit Parts A-B Deliverables – DUE PRIOR TO THE DUE DATE AS ASSIGNED BY YOUR PROFESSOR BIOS252 Week 6 Lab Instructions (B) Page 22 of 24

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