For a majority of human history the only way we could study the brain is to look at it from the outside, we were not able to see the individual building blocks of the nervous system. After revolutionary inventions such as the compound microscope and special stains, scientists discovered that the basic building blocks are cells called neurons.
Neurons are the fundamental element of the brain and nervous system. They allow the brain to send and receive signals. Using electrical and chemical signals, they help coordinate all of the necessary functions of life.
For example, wiggle your toes, now clap your hands, now do the macarena!
To do these actions your brain had to send a signal using neurons down to your toes and throughout your body in seconds.
Crammed inside your brain are about 86 billion neurons and they can send information at speeds of 250 mph. That is a lot of speed just to wiggle your toes.
Let’s look at the parts of a neuron:
The large head of the neuron is called the cell body or soma.
Do you see those crazy tree-like branches coming out of the soma? Those are dendrites.
See that long thin tube extending out of the soma? That is called the axon.
Eventually the axon ends at a certain point. The end point of the axon is called the axon terminal.
How do these interesting looking parts send signals?
First your dendrites receive a signal from other cells. They are like “Hey, I just heard that we need to move our toes.”
The cell body collects all the signals from all the dendrites. They need enough signals to decide whether to go or not.
Once enough dendrites say, “Yeah we should GO” the cell body agrees and begins a process that shoots an electrical signal through the axon.
The electrical signal from the axon reaches the axon terminal. Then the axon terminal fires chemicals out into the next neuron’s dendrites.
Now the next neuron repeats these steps until the signal reaches all the way to wiggle your toes.
Neurons send either excitatory or inhibitory signals. Excitatory signals are like GO signs, they tell the next neuron to send a signal. Inhibitory signals are like STOP signs, they tell the next neuron to not send a signal.
Neurons will not partially fire a signal. For instance it will not fire a signal at 50% or 75% power. It fires at 100% or does not fire at all. There is no in between. They are very decisive.
Now we know that neurons fire signals using electricity and chemicals; axons send a spike of electricity down to the axon terminal and the axon terminal then shoots special chemicals out that tell the next neuron to do a particular action. The electrical spike that shoots through axons is generated by the fascinatingly complex process called action potential.
The chemicals that are shot out of the axon terminal are called neurotransmitters. (Neuro for neurons, transmitters as they are transmitting a message). Neurotransmitters are released into a fluid-filled space that’s between the axon terminal and the next neuron’s dendrites. This space gap is called the synapse. Your brain has about 100 trillion synapses. There are several types of neurotransmitters with unique functions.
Neurons to Complex Thought
How do neurons by only sending GO or STOP signals create complex thought that lets you dream and imagine?
Amazing question!
In fact, scientists do not know the answer yet. We do know that it is the complex interaction of billions of neurons sending trillions of signals that lead to thoughts. However, we are still uncovering the mystery of precisely how it does this.
Glial Cells
Hanging out with your neurons are other variants of cells that we call glial cells. Different glial cell types do special things to support neurons, and recently scientists are discovering they do even more than simply support neurons.
You're a Neuron Master!
Question: If you took a piece of your brain the size of a grain of sand, how many neurons would be in that one piece?
Your brain uses neurons to send and receive information. First dendrites receive signals from nearby neurons, the cell body (soma) collects all these signals and then 100% fires or does not fire, no in between. When the cell body decides to fire, an action potential is generated which sends electricity through your axon until it reaches the axon terminal. The axon terminal then sends neurotransmitters into the synapse which sends information to the next neuron’s dendrites. All this is happening throughout your body at lightning speed!
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