Lesson 2: Inside the Ear
Time Required: One 40-minute class period
Materials: I’m All Ears student worksheet, plastic wrap, bowl or pot with wide opening, uncooked rice, scissors, tape or glue, metal cookie sheet or pan (optional)
This lesson helps students understand the parts of the ear that work together to process sound.
1. Distribute the I’m All Ears student worksheet. Explain that the ear is a complex organ that detects sound and maintains balance. Using the diagram on the student worksheet, discuss the functions of the parts of the ear:
- Pinna—the outer portion of the external ear: sound travels through the outer ear to the ear canal.
- Auditory Canal—the open passage through which sound waves travel to the middle ear.
- Eardrum—a taut, circular piece of skin that vibrates when hit by sound waves.
- Malleus (Hammer), Incus (Anvil), Stapes (Stirrup)—tiny bones that vibrate to amplify sound waves. These are the smallest bones in the body.
- Eustachian Tube—the passageway that connects the ear to the back of the nose to maintain equal air pressure on both sides of the eardrum.
- Cochlea—coiled, fluid-filled structure of the inner ear that contains hair cells called cilia. Cilia sway in response to sound waves, transmitting signals toward the brain.
- Semicircular Canals—fluid-filled structures in the inner ear that detect movement and function as balance organs.
- Auditory Nerve—bundle of nerve cells that carry signals from the sensory fibers to the brain.
2. Demonstrate how the eardrum works with this simple activity. Have students stretch plastic wrap tightly over the opening of a large bowl or pot and sprinkle a teaspoon of rice over the plastic. Ask students to clap their hands close to the plastic wrap. They may also try to create louder noises (such as banging a metal cookie sheet or pan). What happens to the rice?
3. Explain that sounds travel in waves. Those waves make the plastic wrap vibrate, similar to the way that your eardrum vibrates in response to sound. The rice "jumps" when the plastic wrap vibrates. Like the rice, the tiny bones of the middle ear move in response to vibrations in the eardrum.
4. Tell students that they will begin putting together their ear accordion models. The first step is cutting the three pieces of paper along the black lines. Your students will then tape or glue the pieces together to make one strip (Ill.#1). Afterward, the students should fold the paper like an accordion along the dotted lines so that the outer ear is at the top (Ill.#2).
5. Assess what’s been learned about the ear:
- Where is the malleus found? (middle ear)
- Where can cilia be found? (cochlea)
- What’s the most important part of the ear for maintaining balance? (semicircular canal)
- What structures vibrate in response to sound waves? (eardrum, incus)
- Our ears "pop" on airplanes because of pressure changes. What structure makes it possible for the pressure inside our ears to return to normal? (eustachian tube)
- What structure transmits sound signals to the brain? (auditory nerve)
Adapted from EASY MAKE AND LEARN PROJECTS: HUMAN BODY by Patricia J. Wynne and Donald Silver. Copyright © 1999 by Patricia J. Wynne and Donald Silver. Reprinted by permission of Scholastic Inc.