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The Nervous System
The Nervous System
The nervous system is divided into two parts: the central nervous system, and the peripheral nervous system.
- The central nervous system is made up of your brain and your spinal cord.
- The peripheral nervous system is made up of the neurons that go from the spinal cord to the rest of the body.
Neurons
Neurons
Scientists knew for a long time that the body was made of cells, but they didn't know how to research brain cells further. In the late 19th century, Camillo Golgi, an Italian physician, figured out how to stain brain cells to identify the different regions.
This was the resulting image that confused scientists because it didn't look like what they knew cells to look like. Golgi had unofficially discovered the neuron, but Santiago Ramón y Cajal, made the official discovery 15 years later.
How do Neurons Communicate with Each Other?
How do Neurons Communicate with Each Other?
Scientists quickly realized that the neuron is the most important part of the large communication network in almost all animals. However, it wasn't till the 20th century that they realized how neurons communicate in this network- they use the action potential. Here are the different parts of a neuron:
The axon has either a positive or a negative resting potential, which means that when it's at rest, the electrical charge is either positive or negative based on that. The axon terminals of other neurons drop neurotransmitters onto the neuron's dendrites, which pass through the cell body, also called the soma. Depending on the chemicals in the neurotransmitters, the charge is either raised or lowered. If enough chemicals touch the dendrites to raise the charge over the threshold potential, it triggers the action potential, and the neuron is electrocuted. A nerve is a few bundles of axons wrapped together in a small cord.
After that, a pulse of electricity goes through the axon to the terminals, which then touch other dendrites, and releases more neurotransmitters onto those dendrites, which could electrocute other neurons, or they could stay the same.
Action potentials can travel at speeds anywhere between 1 and 100 meters per second. This is partly because there's another cell in the nervous system called the Schwann cell that wraps some types of axons in layers of fat called myelin sheath.
In addition to protecting and insulating the axon, the myelin sheath helps action potentials travel much, much faster.
There are three types of neurons. Most neurons are interneurons, whose job is to communicate with other neurons, and are mostly contained to the brain.
The other two types of neurons are sensory and motor neurons. These two types of neurons make up the peripheral nervous system in the spinal cord, and can be up to a meter long.
Cherry, Kendra, and Steven Gans. “How Neurons Differ From Other Cells in the Body.” Verywell Mind, Verywellmind, www.verywellmind.com/what-is-a-neuron-2794890.
Urban, Tim. “Neuralink and the Brain's Magical Future.” Wait But Why, 20 Apr. 2017, waitbutwhy.com/2017/04/neuralink.html.
Jabr, Ferris. “Know Your Neurons: How to Classify Different Types of Neurons in the Brain's Forest.” Scientific American Blog Network, 16 May 2012, blogs.scientificamerican.com/brainwaves/know-your-neurons-classifying-the-many-types-of-cells-in-the-neuron-forest/.
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