Module 1 The Nervous System

Reflect and Connect

In the Big Picture for this module, you were introduced to the nervous system and communication. Hearing is a very important part of communication. If perception of sound had not been communicated to your brain, how would you have interpreted the events that occurred while you were in the room with your friends?

Reflect on the Big Picture

What might your perceptions have been like in a room like that described in the Big Picture without your being able to hear the laughter, the people talking and perhaps the music playing? How does music at the beginning of a movie help to communicate the tone of movie? What kinds of music communicate dangerous, scary, funny, or romantic scenes? Before a big game, athletes use “pump-up” music for motivation! How do you think Beethoven, who was deaf, was able to successfully convey all of the moods in his music? Sounds in today’s very noisy world are contributing to hearing loss in many people. Knowing now the things you have learned in this lesson, you may be more aware of the volume at the next concert, or the next wedding that you attend. Reflect on the precautions that you could take to protect your ears and your hearing the next time you mow the lawn, ride a snowmobile, listen to your iPod, or use power machinery. What do you notice when you shut the machine off? Could this be a indication of what you should do to safeguard your hearing? In the Get Focused section of this lesson, you could hear the mosquito ringtone of your phone. As you grow older, will you always be able to hear this ringtone, the music you love, the sounds that ensure your survival or those that bring you pleasure? Judging by your own habits when it comes to hearing,do you think that you might have to wear a hearing aid at some point in your lifetime?

Module 1: Lesson 6 Assignment—Part 3

Hearing Technologies Research

Discuss

Consider the following scenario:

Ethan was very excited to have landed a job as an assistant baggage handler at the airport. He got to drive the baggage train, and load and unload suitcases and parcels from airplanes. However, he found that the ear protection that he was supposed to wear was hot and cumbersome. He took it off whenever he could and sometimes he forgot to put it back on when the big jets came in or took off. After two years on the job, he began finding that was having difficulty hearing. It was suggested that he purchase a very expensive new type of hearing aid that would greatly improve his hearing. Ethan was very upset because his medical plan did not pay for hearing aids.

• Do you think that hearing aids should hearing aids be covered by our medical plans? Keeping Ethan’s story in mind, suggest several reasons why they should and several reasons why they should not. Using the discussion board, share and discuss the reasons supporting your argument as well as those that counter your argument. Share your final “for and against” reasons with your instructor. 

Lesson Summary

In this lesson, the following focusing questions were investigated:

• What are the major parts of the ear that facilitate your response to sound in the environment?

• How do the structures of the ear impact your ability to maintain balance within your changing environment?

You should now be familiar with the structures and functions of the outer, middle, and particularly the inner ear. Located in the inner ear, both the cochlea, adapted for hearing, and the vestibular apparatus, adapted for maintaining balance, rely on specialized hair cells to change mechanical energy of sound or movement to the electrochemical energy of a nerve impulse. The structures of the outer and middle ear conduct and amplify sound waves so that pressure waves can be created in the cochlea of the inner ear. The frequency of a sound wave results in your perception of pitch, whereas the amplitude (height) of the sound wave results in your perception of loudness. Conduction deafness and perception (nerve) deafness result when there is a dysfunction in the hearing apparatus.  Both dynamic and static balance are maintained by the vestibular apparatus, which includes the semicircular canals, the utricle, and the saccule.  Technologies, such as hearing aids and cochlear implants have been developed to help us deal with hearing loss.

 

Lesson Glossary

amplitude: the extent of a vibration; see intensity

auditory canal: a short channel that funnels sound waves from outside the ear to the ear drum or tympanum; it amplifies sound waves thereby making sounds louder

auditory nerve: a nerve composed of sensory fibres from the organ of Corti the vestibular apparatus which conducts impulses to the temporal lobe of the cerebrum

basilar membrane: one of two parallel membranes that comprise the organ of Corti in the inner ear (the other being the tectorial membrane); hair cells are attached to it

cochlea: contains the organ of Corti which functions to convert the mechanical energy of sound waves into a nerve impulse

dynamic balance (rotational equilibrium): balance resulting when the head and body are moved or rotated

 Eustachian tube: tiny passageway extending from the middle ear to the throat (pharynx); plays an important role in equalizing air pressure on both sides of the tympanum

 frequency: number of wavelengths per given time; number of waves that pass a given point in a given time

 hair cells: sensory mechanoreceptors attached to the basilar membrane in the organ of Corti within the inner ear

incus (anvil): the middle in the sequence of the three ossicles located in the middle ear; connected to the malleus and the third ossicle (stapes); part of a lever system which amplifies sound waves

inner ear: one of the three regions of the ear that is located deepest into the head and consists of a fluid filled chamber which contains the semicircular canals, the utricle and saccule, and the cochlea

intensity: measurement of the difference between compressed and rarefied areas of a sound wave used in physics; corresponds to amplitude of a wave

loudness: subjective interpretation of sound intensity

malleus (hammer): the first in the sequence of the three ossicles located in the middle ear; connected to the tympanum and the second ossicle (incus); part of a lever system which amplifies sound waves

middle ear: one of the three main regions of the ear which begins just past the tympanum and consists of a chamber containing three tiny bones (ossicles) called the malleus (hammer), the incus (anvil), and the stapes (stirrup);  leads into to a minute opening called the Eustachian tube

organ of Corti: contains hair cells that detect vibrations in the fluid of the inner ear and initiates a nerve impulse that is transmitted to the auditory nerve

ossicles: three tiny bones located in the middle ear that are connected to each other , to the tympanum, and to the oval window; involved in amplifying sound waves

otoliths: tiny particles of calcium carbonate found in the utricle and saccule that contact the hair cells of these structures and stimulate them

outer ear: one of the three main regions of the ear (outer ear, middle ear, and inner ear) which consists of the pinna and the auditory canal; ends at the tympanum or eardrum

oval window: a membrane covered opening located between the chamber of the middle ear and wall of the inner ear; the stapes (stirrup) is attached to it and transmits sound waves by it to the inner ear

pinna: the outer flap of the ear composed of skin and cartilage and shaped so that it funnels sound waves into the auditory canal, thereby enhancing them

pitch: corresponds to the frequency of a sound wave

round window: a membrane covered opening located between the chamber of the middle ear and the inner ear, and below the oval window; functions in dissipating sound waves in the inner ear

sebaceous gland: tiny glands in the auditory canal that produce wax

semicircular canals: three tubes that are situated at right angles to one  another; contain mechanoreceptors that detect head and body rotation; responsible for dynamic balance, or rotational equilibrium (rotational equilibrium dynamic balance), which is the balance that is established in response to the head and body being moved or rotated

sensory neurons: nerve cells that are stimulated by hair cells in the organ of Corti to conduct messages toward the temporal lobe of the brain

sound: pressure disturbance beginning at a vibrating object (source) and spread out by a medium such as air

sound wave: a series of compressions and rarefactions resulting in an S-shaped curve or sine wave

stapes (stirrup): the third in the sequence of the three ossicles located in the middle ear; connected to the second ossicle (incus) and the oval window; part of a lever system which amplifies sound waves and causes vibrations in the fluid of the inner ear

static balance (gravitational equilibrium): balance resulting from changes in the position or the movement of the head in one direction; usually in response to gravity

tectorial membrane: one of two parallel membranes (the other being the basilar membrane) that is found in the organ of Corti; during the transmission of sound waves, the basilar membrane vibrates and causes the sensory hairs to flex against the tectorial membrane

tympanum: a round elastic structure that vibrates in response to sound waves; also called the eardrum or tympanic membrane

utricle and saccule: tiny chambers in the inner ear that contain hair cells which respond to changes in head position with respect to gravity and movement in one direction; responsible for static balance, or gravitational equilibrium

vestibule: fluid-filled area of the inner ear located between the semicircular canals and the cochlea; contains the utricle and saccule