Parts of the Brain
Let's start with an overall picture of the brain. There are four major parts, and each has a special job. The brain stem, the cerebellum, the limbic system, and the cerebral cortex grow in a specific order, beginning with the brain stem. This is followed by the cerebellum, the limbic system, and finally the cerebral cortex.
- brain stem- in charge of basic survival functions, like breathing and your heartbeat.
- cerebellum - in charge of things you do by reflex, like blinking and swallowing.
- cerebral cortex - in charge of the things you do on purpose, like throwing and catching.
- limbic system - in charge of storing emotions.
It's important to know that the limbic system is also responsible for storing the positive emotions that lead to strong attachments. More about that later.
Digging Deeper - The Neurology of the Brain
Understanding the neuron, the basic unit of the brain, will show us how your brain works as a community that helps you understand your world.
The neuron: The brain is made of billions of very active cells called neurons. Believe it or not, you went through the process of neurogenesis before you were even born. Neurogenesis is the creation of neurons through cell division. At this time, you have more neurons than you will ever need. In fact, you'll only add a few more later on in life. Your brain, as a baby, made about twice as many neurons as it needed. Why make so many neurons? Your body does this to make sure you have plenty of opportunities to learn and grow.
Neurons have four parts: a cell body, dendrites, axons and synapses. Neurons talk to each other using electrical signals, kind of like pathways that let all your thinking happen.
Understanding the Neuron and its Parts
Like the captain of a spaceship, the cell body is the control center of the neuron. This is where information is collected and the decision is made whether or not to send it on to other cells. The cell body, as the captain, decides if the electrical signal coming in is strong enough. If so, the cell body opens the door and lets the electrical information flow out. We call this your brain making connections.
Dendrites are like tree branches that reach from the cell body. They look and listen for messages being sent from other neurons. Amazingly, one neuron can have hundreds of dendrites that spread out in your brain to information from other neurons. In your brain right now there are some neurons that are connected to as many as 15,000 other neurons.
The axon looks like another branch coming out of the cell body, but it puts information out instead of letting information in, as the dendrites do. Axons and neurons need a lot of energy to enter and exit the cell body. If the signals coming or going aren't strong enough, their electric signal is not passed on. If it is strong, the signal passes very quickly.
Lastly, a synapse is the place where an axon and dendrite connect. As you've been growing and learning, thousands of connections have been made and organized as you experience your world. In fact, in your first ten years, your brain may form trillions of synapses, and lose many as well. Why does this happen?
Connections Come and Go
When neurons connect and disconnect with other neurons, it makes a web of neural sidewalks. Remember, the job of the neuron is to send messages to other neurons to make connections. These electrical and chemical signals, or 'talking' between neurons in different parts of your brain and body, are what allows you to do simple things, like pick up a cup, to complex things, like remember a math problem.
What makes a signal strong? Neuroscientists say 'if it fires together, it wires together'. That means that when you make connections, the signal is stronger. The first time your teacher talks about fractions, for example, the words numerator and denominator are new to you - they have nowhere to connect. But the next time she says the words, or you read them, an electrical impulse is fired with the memory of the last time you heard these words. Your memory is getting stronger. By the time you're finished with your unit on fractions, you're a numerator and denominator genius! The connection is solid.
Special neurons called sensory neurons carry messages from the sense organs, like the eyes and ears, to the brain. Motor neurons send messages from the brain or spinal cord to make muscles move. Everything you do, from blinking to biking, happens because neurons are constantly sending messages to each other and the rest of the body. Learning, thinking, remembering, and making decisions all happen because neurons communicate with each other in the brain and the body.
How to Build a Strong Brain
The things you do play a very important role in your brain development. Neuroscientists tell us that every time we repeat an experience, connections become stronger. When you're young, neurons form many connections that you won't need later on in life. The connections that are used more stick around. Connections that are not used often enough may be pruned, or lost. So, what you do and the things you experience are important in forming a strong brain. Rich activities, like reading, playing outside, having conversations with friends and family, and interacting with your environment are important. They strengthen the connections and make your brain a lot more ready and able to make new ones. Not enough quality activities can mean your brain isn't making strong connections, or that the connections you do have may become weaker.
Now that you're an expert, you can teach other people about the brain. Use your hands and arm as models to show parts of a neuron. Your palm is the cell body, and your fingers are the dendrites. Remember, there are a lot more dendrites than fingers, and your fingers don't branch at the ends like dendrites do, but you can explain all that. Your arm and other hand can represent the axon. Now you're ready to show neurons connecting by spreading out the fingers on one hand and bringing them close to (but not quite touching!) the fingers on your other hand, which, of course, are spread out too. Tell about how the dendrite is sending and axon is receiving the information, and point out the difference between the axon, your arm, and the axon tips, your finders (see photo). Tell how the space between your hands is the synapse, the carrier of electrical impulses. And, all those sensory and motor actions you're using? Yep, you have your amazing brain to thank for that!
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Learning About the Brain
As discussed in the lesson, the four major parts of the brain are the brain stem, cerebellum, cerebral cortex, and limbic system. The cerebral cortex, brain stem, and limbic system are all composed of multiple structures. First, research the individual structures that make up these brain components. Next, create a model of the brain. You may choose to draw an image of the brain or build it using various materials such as cardboard and markers. Once your model is complete, label the individual components that make up the brain stem, cerebral cortex, and limbic system. Also, label the cerebellum. With your model, include an information sheet that illustrates which individual components make up each brain structure, that is the brain stem, cerebral cortex, and limbic system, as well as the main function of each of these individual brain components.
Consider what you have learned about the neuron and each component, the cell body, dendrites, axon, and synapse.
- What would happen to the neuron as a whole if the cell body was damaged?
- What would happen to the neuron as a whole if the dendrites were damaged?
- What would happen to the neuron as a whole if the axon was damaged?
- What would happen to the neuron as a whole if the synapse was damaged?
- What would be the effect overall concerning building strong brain connections, if a neuron is damaged?
The following are example answers to the above questions:
- Damage to the cell body may result in inappropriate transmission, or lack of transmission, of incoming signals to other neurons.
- Damage to the dendrites would result in a lack of detection of signals from other neurons, which would impair the continued transmission of the signal.
- If the axon of the neuron is damaged, the signal would not reach the synapse, and thus, would not be passed on to the next neuron.
- Damage to the synapse between two neurons would impair the transmission of the signal from one neuron to the next neuron.
- Damage to a neuron that is associated with a specific brain connection, for example, reading, may result in weakening of that connection, and thus, may make performing the specific task more challenging.
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