Good afternoon!
5.1. What is the role of the eyelids?
Answer 5.1. The eyelids protect the eyes.
5.2. Which four accessory glands or structures help lubricate the eye?
Answer 5.2. The tarsal glands, ciliary glands, conjunctiva, and lacrimal glands all contribute to lubricating the eye, though their secretions differ.
5.3. What is the role of lysozyme in tears?
Answer 5.3. Lysozyme is a component of tears that helps to destroy bacteria and protect the eye from infection.
5.4. What is the visual role of the external eye muscles?
Answer 5.4. They direct the eyeball toward what you wish to view.
5.5. What is the meaning of the term blind spot in relation to the eye?
Answer 5.5. The blind spot contains no photoreceptors; it is the site where the optic nerve leaves the eyeball.
5.6. What function does the choroid of the vascular layer have in common with the pigmented layer of the retina?
Answer 5.6. Both contain pigment, which prevents light scattering in the eye.
5.7. How do the rods and cones differ from each other?
Answer 5.7. Rods have a rodlike outer segment containing the photopigment, whereas cones have a shorter cones-shaped outer segment. Rods respond to low light conditions and produce black-and-white vision; cones need bright light and provide color vision.
5.8. What are the refractory media of the eye?
Answer 5.8. Refractory media include the cornea, aqueous humor, the lens, and vitreous humor.
5.9. What name is given to the ability of the eye to focus on close objects?
Answer 5.9. Accommodation.
5.10. What is the difference between the optic tract and the optic nerve?
Answer 5.10. The optic nerves leave the eyeballs, and the medial half of the fibers of each optic nerve cross over to the opposite side, joining there with the fibers from the outside half of the opposite eye to form the optic tracts.
5.11. In what way does the photopupillary reflex protect the eyes?
Answer 5.11. It causes pupillary constriction in very bright light. Intense light stimulation can injure the photoreceptors.
5.12. How is astigmatism different from myopia and hyperopia?
Answer 5.12. Astigmatism results from unequal curvatures on the lens surface, not from an eyeball that is too long or too short to focus the image on the retina. The unequal curvatures of astigmatism result in points of light that focus on the retina as lines, not points, leading to blurry images.
5.13. Which region(s) of the ear (external, middle, or internal) serve hearing only?
Answer 5.13. External and middle ears serve hearing only.
5.14. Which structures of the ear transmit sound vibrations from the eardrum to the oval window?
Answer 5.14. The ossicles (hammer, anvil, and stirrup).
5.15. What sense do the vestibule and semicircular canals serve?
Answer 5.15. Balance or equilibrium.
5.16. Describe the different receptors for static and dynamic equilibrium and their locations.
Answer 5.16. Dynamic receptors located in the semicircular canals (crista ampullaris) have embedded in the gel-like cupula; static receptors located in the vestibule (maculae) have otoliths that move when the head moves, causing hairs embedded in the otolithic membrane to bend.
5.17. What are otoliths, and what is their role in equilibrium?
Answer 5.17. Otoliths are tiny stones made of calcium salts that are located in the maculae of the vestibule. They respond to static equilibrium cues relative to the position of the head in space.
5.18. From the air outside the body, through what substances do sound waves travel to excite the receptor cells of the cochlea?
Answer 5.18. Tympanic membrane to bones of ossicles to fluids of the cochlear scale.
5.19. Which nerve transmits impulses from the spiral organ of Corti to the brain?
Answer 5.19. Cochlear nerve (division of cranial nerve VIII).
5.20. Do high-pitched sounds peak close to or far from the oval window?
Answer 5.20. Close to the oval window.
5.21. How do sensorineural deafness and conduction deafness differ from each other?
Answer 5.21. Sensorineural deafness results from damage to neural structures involved in hearing (cochlear nerve, auditory region of the brain), whereas conductive deafness results from anything that prevents sound vibrations from reaching the cochlea (earwax, fusion of the ossicles, fluid in the middle ear).
5.22. What general name is used to describe both taste and smell receptors? Why?
Answer 5.22. Chemoreceptors, because they respond to chemicals in solution.
5.23. Where, relative to specific structures, are most taste buds located?
Answer 5.23. On the tongue.
5.24. Why does it help to sniff substances that you want to smell?
Answer 5.24. Odor receptors are located at the superior aspect of the nasal cavity. Sniffing brings the air upward.
5.25. Fifty-year-old Mrs. Bates is complaining that she can’t read without holding the newspaper out at arm’s length. What is her condition, and what is its cause?
Answer 5.25. Presbyopia; caused by reduced elasticity of the lens as a result of aging.
5.26. Which of the special senses is least mature at birth?
Answer 5.26. Vision.
5.27. What is presbycusis?
Answer 5.27. Deafness of old age.
Good luck in your studies!