Discuss the role of models in science; in particular, the models of the brain students use in this unit.
Draw students' attention to the Key Ideas using means such as posters and overhead transparencies.
Begin section with Activity 3-1: Picture a Nerve Cell to introduce the structure and function of a neuron.
Explain how nerve impulses move from one neuron to another by connecting neuron diagrams to create synapses.
Explore the structure and function of the neuron by having students use their neuron diagram to complete the Mini Activity: Building a 3-D Model of a Neuron.
Emphasize that neurons carry messages in one direction only.
Do Activity 3-2: Drug Effects on Neurons to illustrate how information is carried through the synapse by neurotransmitters.
Provide the opportunity for students to share the models of the neuron with the class.
Emphasize that the nerve impulse is electrical as it passes along the dendrite, cell body, and axon of the neuron, and chemical as a neurotransmitter crosses the synapse.
Time permitting select from unit projects.
Throughout and at the end of the section refocus students' attention on the Key Ideas.
You have read about neurons being like a big bedroom with tentacles and a nerve impulse being like an electrical signal. These explanations are analogies and they help us picture the activities of these parts of the nervous system. What other analogies can you think of to help you learn more about neurons? What analogies can you think of to describe a nerve impulse? Draw pictures to illustrate your analogies.
Building a 3-D Model of a Neuron Suggestions for materials include markers, crayons, colored pencils, scissors, colored paper, tape, glue, clay, oranges, apples, balloons (to represent cell bodies), wire, string, and yarn (to represent axon and dendrites). Have students place 2 or 3 neurons close to each other, but not touching, to create a reflex arc. Identify the synapse (space between neurons) where the neurotransmitter helps carry the impulse across the gap to the next neuron. When finished, display neuron models by hanging them (on string or tape) from the classroom ceiling or on the wall. The nerve impulse can be simulated by using a string of holiday lights (in sequence mode) to represent the electrical part of the message traveling down the axon. Food coloring added to a vial of water positioned between neurons can represent the chemical part of the impulse. Invite a guest speaker to address topics such as surgery, headaches, slipped disk, whiplash, or seasonal affective disorder.