1. Module 1

1.38. Page 5

Lesson 6

Module 1—The Nervous System

Try This

 

TR 1. To ensure that you understand the mechanisms of the inner ear involved in hearing, complete this drag-and-drop activity about the organ of Corti. If you have any questions about the inner ear, ask your teacher.

 

Self-Check

 

The following Self-Check questions will help you review the concepts of the outer, middle, and inner ear. Consult with your teacher if you are not able to give complete answers. Store your answers in your course folder.

 

SC 11. Imagine that you are a sound wave. In order, describe the structures of the ear that you would encounter, starting with the outer ear and finishing with the organ of Corti.

 

SC 12. What happens to the energy of sound waves, which travel through air, once they reach the tympanum?

 

SC 13. How is the surrounding medium of the inner ear different from that of the middle ear? What needs to happen to the vibrations in the middle ear in order to accommodate this difference?

 

SC 14. What is the role of the hair cells located in the organ of Corti?

 

SC 15. Nerve impulses initiated in the organ of Corti are sent to which part of the brain?

 

Check your work.
Self-Check Answers

 

SC 11. In correct sequence, sound waves encounter the following structures:

 

pinna, auditory canal, tympanum, ossicles (malleus, incus, and stapes), oval window, cochlea, organ of Corti

 

SC 12. When the energy of sound waves comes in contact with the tympanum, it causes it to vibrate. Its vibrations are passed on and amplified by the neighbouring ossicles. At this point, the sound energy has been transformed into mechanical energy. Each bone vibrates more than the previous one so that the vibrations are amplified as they pass from one to the other. The last bone concentrates the vibrations onto the oval window. The vibrations, in turn, cause the fluid in the cochlea to vibrate, creating pressure waves that initiate an electrical nerve impulse in the auditory nerve.

 

SC 13. The middle ear is filled with air, whereas the inner ear is filled with fluid. In order to convert the sound vibrations of the middle ear into the pressure waves of the inner ear, the sound vibrations need to be amplified a great deal. It is much harder to move fluid than it is to move air.

 

SC 14. The role or function of the hair cells is to initiate a nerve impulse in the auditory nerve when they are stimulated by the pressure waves in the fluid of the inner ear.

 

SC 15. The auditory nerve transmits nerve impulses initiated by the hair cells to the temporal lobe of the cerebrum. Note: Biology 30 students require a more sophisticated and detailed answer than just simply “the cerebrum”!

 
Watch and Listen

 

To consolidate your understanding of the concepts up to this point, go to the McGraw-Hill Ryerson online learning centre at www.albertabiology.ca. This site has many resources. Click on “Student Resources” in the column on the left side of the screen. Click on the “continue” button. You should now be on the main Inquiry into Biology page. Listed on the left side of the screen are many resources that are available to you. Click on “Essential Study Partner” in the left column. Then, click on “Essential Study Partner” in the white part of the screen. Next, click on the “Animals” icon. Choose “Sense Organs” from the list at the left, and then click on “6.81 Sounds Waves.” Watch an animated clip that shows how sound waves are captured, transformed into mechanical vibrations, amplified, and finally converted into nerve impulses that are transmitted to the brain—all by the different structures of the ear.

 

OR

 

You may want to watch a video about the anatomy and physiology of the ear. Watch the following segments of the video “The Ear: Hearing and Balance: 'Sound Sense'.”

  • “Processing of Sound Waves”
  • “Ear Structure”
  • “Detailed Anatomy of the Ear”
  • “Bio Fact: Bones of the Middle Ear”
  • “Ear Function”
  • “Detailed Physiology of the Ear”

 

Self-Check

 

A diagram shows the auditory system in cross-section. Refer back to the diagram on page 3 for a listing of the regions of the ear and the parts within each of these regions.

Inquiry into Biology (Whitby, ON: McGraw-Hill Ryerson, 2007), 420, fig. 12.20. Reproduced by permission.

 

SC 16. Which three parts of the ear are involved in amplifying sound waves?

 

SC 17. The initiation of nerve impulses occurs in which structure?

 

SC 18. Which structure first directs sound waves into the ear?

 

SC 19. Which structure aids in the equalization of pressure between the outer and inner ear?

 

SC 20. Which structure is most affected if pressure is not equalized?

 

SC 21. Where is the organ of Corti located?

 

SC 22. Middle ear infections affect which structure?

 

SC 23. In the ear, which structure is considered analogical to the optic nerve in the eye?

 

SC 24. Where are the wax glands located?

 

SC 25. Which structure causes the ossicles to vibrate?

 

Check your work.
Self-Check Answers

 

SC 16. The auditory canal, tympanum, and ossicles amplify sound waves.

 

SC 17. The initiation of nerve impulses occurs in the cochlea; more specifically, the organ of Corti.

 

SC 18. The pinna directs sound waves into the ear.

 

SC 19. The Eustachian tube assists in balancing pressures between the outer and inner ear.

 

SC 20. The tympanum is most affected if the pressures are not equalized.

 

SC 21. The organ of Corti is located in the cochlea.

 

SC 22. Middle ear infections affect the tympanum.

 

SC 23. The auditory nerve is analogical to the optic nerve.

 

SC 24. The wax glands are located in the auditory canal.

 

SC 25. The tympanum causes the ossicles to vibrate.