Written by Bedirhan Atabay
The nervous system connects our brain with the rest of our body which can be divided into two parts: the central and peripheral nervous systems. The central nervous system includes the brain and spinal cord. Meanwhile, the peripheral nervous system consists of the nerves that connect the central nervous system to the rest of the body.
The nervous system consists of neurons, and there are the most crucial structure for the system. They need to work together to carry the signals from the brain all over the body. There are three types of neurons; Sensory Neurons, Motor Neurons, and Interneurons. Sensory neurons help us to have senses. They are the main reason for our sensations. Tasting, hearing, and smell can be shown as examples. These neurons can notice the differences that happen to our bodies or around us. For example, when you touch the ice, you can feel how cold it is. This is due to your ability to feel, and you get this ability through your sensory neurons. Motor neurons are responsible for movement. Motor neurons carry the information about our movement from our brain to the rest of our body. They have two kinds: lower motor neurons and upper motor neurons. Simply, upper motor neurons carry the information from our brain to our spinal cord, meanwhile lower motor neurons carry the information from our spinal cord to the rest of our body. Interneurons are the third type of our neurons. Fun fact, more than 99% of our neurons are interneurons which is an extreme percentage. Our body contains more than 100 billion interneurons, this number is also massive. They carry the information from sensory neurons to motor neurons. They can carry the information to each other too. Interneurons help to stabilize the neuronal activity in our brain by secreting GABA, or Gamma-Aminobutyric Acid. GABA is a transmitter that is responsible for decreasing the neuronal activities. GABA is able to reduce stress and anxiety, and it also is capable of improving sleep (1).
Neurons can be in five major forms: Unipolar Neurons, Bipolar Neurons, Pyramidal Neurons, Purkinje Neurons, and Multipolar Neurons. Unipolar neurons are neurons with only one dendrite. They only exist in invertebrates. Bipolar neurons are neurons with two dendrites. They only exist in specific parts of our body, such as the retina of our eye. Pyramidal neurons have only one axon, but they have several dendrites that form the shape of a pyramid. They are the largest type of neurons. Purkinje neurons have several dendrites. Purkinje neurons are involved in keeping the other neurons from firing. They release transmitters to do so. Multipolar neurons have several dendrites. Multipolar neurons are the most common neurons in our nervous system.
Neurons are crucial for the functioning of our Nervous System. Without them, the structure we define as Nervous System wouldn’t have existed. With its various types and forms, each Neuron has different features than the other, and these differneces is what make s this topic more interesting.
References:
Gamma-Aminobuytric Acid (GABA), My Cleveland Clinic, https://my.clevelandclinic.org/health/articles/22857-gamma-aminobutyric-acid-gaba.
Nervous System, My Cleveland Clinic, https://my.clevelandclinic.org/health/articles/21202-nervous-system.
Nervous System, Larissa Hirsch, MD, https://kidshealth.org/en/parents/brain-nervous-system.html#:~:text=What%20Is%20the%20Nervous%20System,brain%20down%20through%20the%20back.
What is a Neuron, Medical News Today, https://www.medicalnewstoday.com/articles/unipolar-vs-bipolar-vs-multipolar-neurons#about-neurons.
An Easy Guide to Neuron Anatomy with Diagrams, Healthline, https://www.healthline.com/health/neurons#types.
Interneurons, Physiopedia, https://www.physio-pedia.com/Interneurons.
Three groups of interneurons account for nearly 100% of neocortical GABAergic neurons, Wiley Online Library, https://onlinelibrary.wiley.com/doi/10.1002/dneu.20853.
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