Chapter 8 Lesson 6 "The Sense Organs"

Materials:

• Optional Materials: sugar, lemon, salt, bitter food: bits of apple, or onion. (for some independent taste tests)
• Notes for lesson 8-6
• Worksheet for 8-6
• Lab activity, Sensory Receptors in the Skin.

Objective:

• .Students will explain how the eyes "see" objects.
• Students will trace a sound wave as it travels through the ear.
• Students will name the four kinds of messages that receptor cells in the skin receive.
• Students will describe how the senses of taste and smell work together.

Alaska Content Standards:

• SCI A-10 Students will understand that living things are made up mostly of cells and that all life processes occur in Cells (Cells)
• SCI A-12 Students will distinguish the patterns of similarity and differences in the living world in order to understand the diversity of life and understand the theories that describe the importance of diversity for species and ecosystems.

Anticipatory Set: Students will start a discussion about what their body is sensing right now. Think about all five senses. What are your five senses? Develop a list.

What is your most important sense? Why? Rank the senses in importance to you. Each site will elect a recorder and record the number of students that feel each sense is the most important. The teacher will bring all the information together using this form to determine with sense students feel is the most important.

Teacher Input: Show a picture of the eye and explain how your eyes convert light into electrical energy sent over nerves.

Light rays enter the eye through a transparent layer of tissue known as the cornea. As the eye's main focusing element, the cornea takes widely diverging rays of light and bends them through the pupil, the dark, round opening in the center of the colored iris.The lens of the eye is located immediately behind the pupil. The purpose of the lens is to make the delicate adjustments in the path of the light rays in order to bring the light into focus upon the retina, the membrane containing photoreceptor nerve cells that lines the inside back wall of the eye. The photoreceptor nerve cells of the retina change the light rays into electrical impulses and send them through the optic nerve to the brain where an image is perceived.

Show a picture of a cataract and explain that there are many problems that can cause the loss of eyesight. Have the students name them. What happened to the eye in this picture?

Show this series of pictures and trace a sound wave as it ravels through the ear. Ear1, Ear2, Ear3, Ear4, Ear5, Ear6, Ear7, Ear8.

Sound vibrations, or sound waves, are collected by the outer ear (those are the things hanging on the sides of your head!) and travel into the ear canal, where they bump up against the eardrum. The ear drum vibrates in sympathy with these sound waves. As it vibrates, it moves a series of tiny bones in the middle ear, which carry the vibrations to a fluid-filled tube called the cochlea in the inner ear. The fluid inside the cochlea vibrates a series of tiny hairs called cilia, which are attached to auditory nerves. The movement of these cilia stimulates the nerves, and they send signals to the brain, which, in turn, processes these signals into the sounds we hear.

Show this picture of the tongue and explain how we taste. First explain The actual organ of taste is called the "taste bud." Each taste bud (and there approximately 10,000 taste buds in humans) is made up of many (between 50-150) receptor cells. Receptor cells live for only 1 to 2 weeks and then are replaced by new receptor cells. Each receptor in a taste bud responds best to one of the basic tastes. A receptor can respond to the other tastes, but it responds strongest to a particular taste.

Ask, how is the sense of smell related to the sense of taste. When you swallow your food the smell of the food travels back into your nasal cavities as you breath further enhancing the flavor.

Modeling: Show the ADAM CD of the five senses.

Check for Understanding: Go through the question on P195 with the students and see how they do. It is on the notes sheet.

Closure: Have the students plug their nose and take a bite of the different foods. See if they can tell the differences.

Independent Practice: Students will complete the Workbook Activity, and will take the quiz on Lesson 6. Optional the Sensory Receptors in the Skin Lab activity.

Duration:

2 Periods, 30 minutes + 10-15 for Independent Practice (Could be longer if taken for homework).