The nervous system is made of various types of cells, mainly neurons and glia. In this text, we will focus on understanding neurons. Each neuron is composed of different parts:
The dendrites are like little branches that are continuously sensing signals. They have receptors on their surface to detect “messages” from other neurons.
The soma is the cell body of the neuron, and it includes the nucleus and other organelles.
The axon is typically a “tube” that connects the cell body with the axon terminal. They link different regions of the brain and body (for example, the longest axon in an adult body is the sciatic nerve, measuring around one meter and connecting our lower back with our legs and feet) [2,3]. Some axons can be covered in a substance called myelin to enhance and speed up the electric transmission of impulses. The “endpoint” of the axon is the axon terminal, where the neuron typically stores the neurotransmitters (chemical substances that travel between neurons to help them “communicate”).
Figure 1. Structure of the neuron [1].
In an image of the brain, there are two main colors: grey and white. Visually, we can identify white matter regions, which include the myelinated axons, and grey matter regions, which include the dendrites, neuronal cell bodies, and some neurons without myelin [4]. For example, the cortex of the brain (the outer layer) is made of grey matter, and there are also some grey matter centers hidden underneath the cortex (some of these subcortical structures can be very important in processes like memory and emotion). On the other hand, a significant part of the subcortical region (the region underneath the cortex) is white matter, and it includes the myelinated axons connecting the brain areas (like wires connecting one region to the other).
However, the question remains – how do these neurons “communicate”? Stay tuned for future posts where we’ll understand how neurons “talk” to each other!
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Written by: Nicole
Edited by: Natasha
Figure created by: Storyset (Freepik)
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References:
Structure of the neuron. Image by storyset on Freepik. Available at: https://www.freepik.com/free-vector/nerve-cell-concept-illustration_37452681.htm#query=neuron&position=3&from_view=keyword&track=sph
Muzio MR, Cascella M. “Axon Histology” [Updated 2022 Nov 14]. StatPearls Publishing. Available at: https://www.ncbi.nlm.nih.gov/books/NBK554388/
Giuffre BA, Jeanmonod R. “Sciatic Nerve Anatomy” [Updated 2022 Jul 25]. StatPearls Publishing. Available at: https://www.ncbi.nlm.nih.gov/books/NBK482431/
Thau L, Reddy V, Singh P. Anatomy. “Central Nervous System” [Updated 2022 Oct 10]. StatPearls Publishing. Available at: https://www.ncbi.nlm.nih.gov/books/NBK542179/
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