Billions of Neurons in the Brain
When teaching brain anatomy, it is essential to go over the neuron — the cells of the nervous system. Explain to students that the brain has over 100 billion neurons, according to the University of Washington. Point out that neurons are similar to other types of cells because they perform basic cellular functions and have the same components, like a nucleus, cell membrane and other organelles; but they have a different structure and function than other cells. Students can refer to the accompanying study guide for further help.
Diagram of a Neuron
When teaching the neuron, start by going the parts of a neuron. Use an image of the neuron with labels for each of the major parts, such as the image on the left. Next to the number, write down the name of the part next to the neuron diagram. For example, it should look like:
- Nodes of Ranvier
- Axon Terminals
- Myelin Sheath
- Cell Body (Soma)
Give students handouts and ask them to fill in the blanks. Encourage students to write down the functions of each part next to the name when studying.
After the different parts of a neuron has been covered, move on to the function of a neuron. Explain that the neuron passes the signal along, which is essential for brain communication. When explaining the function, use the image to illustrate.
Explain to students that the signal comes to the neuron through the dendrites at the top of the neuron, passes down the axon, and travels on to the next neuron. Point out that the myelin sheath protects the axon and helps send the signal on. At this point, introduce the action potential, and how the transportation of electrical signals down the neuron is involved. Before moving on, make sure that the students understand the concepts.
For this part of the lesson, divide the types of neurons into two groups: by function and by extension number. When teaching the functional types, explain to students that there are three types: sensory neurons, motor neurons and interneurons. Point out that the sensory neurons send information towards the central nervous system, the motor neurons send information away from the central nervous system, and the interneurons relay messages between the sensory and motor neurons. Do an exercise: write out one function per flash card, and pass them out to students. Have them read the flashcards out loud, and ask other students to answer what type of neuron it is.
For the second categorization group, draw each one on the blackboard or use a printed image. Explain to students that bipolar neurons have two extensions from the cell body; pseudounipolar neurons have two axons; and multipolar neurons have multiple extensions, but only one axon. Pass out a worksheet for students to review the different types of neurons.
- University of Washington: Types of Neurons, http://faculty.washington.edu/chudler/cells.html
- Image Credit: Neuron by NickGorton under CC by -SA 3.0
- University of Washington: Action Potential, http://faculty.washington.edu/chudler/ap.html