The Neuron: An Introduction

Right now, modern technology is progressing at incredible rates - even feeling axon transmission fast!
As these technologies merge with the personal health and optimisation worlds, the neuron and its workings are becoming more and more of a focal point. And for good reason. As human populations stretch into longer life-spans, so increases the battle with neuronal and cognitive function decline.

Think Dementia, Parkinson’s, Alzheimer’s.

The good news? In this age of technology and modern nutrition, there is plenty that an informed person can do to protect their neurons and their function. It is important to start as young as possible, these conditions are not just the flip of a switch. These are a progressive decline. Alzheimers has even shown predictive measures that can be taken 15 years before symptoms show. [1] But first, to get informed.

Stepping in, our VitaKea series… The Neuron!

With this group of articles we will be looking to cover the well-established understanding on the neuron and related systems. But as a fresh-face-friendly introducer, this article will guide you through the principle function of a neuron, overview the key components that make a neuron, and the process by how it operates. This providing the foundations to dive in a little deeper in the discussions to come. But enough ado, there is a whole world of cell and molecular biology awaiting you!




What do neurons do?


Neurons (aka. nerve or neuronal cells) are perhaps the most animating component of what makes you act and function as your unique self. Within this family of cell types, they provide a massive array of functions all throughout the body, all with one common attribute.

Neurons are cell structures which perform to communicate stimuli from one point, to the next.

These neuronal structures are located throughout your entire body in one large lattice network. Varying from sizes easily visible to the eyes, down to microscopic. Neurons are responsible for how you engage and signal all your active bodily movements.
This includes even the unseen, such as your thoughts, making decisions and accessing memories. Also movements that are both conscious or not, say typing on your keyboard as well as the beating your heart in your chest. Additionally, all of how you receive information from the world. It doesn’t matter if it’s through touch, hearing or another means, all these are processed by neuronal cells. There are actually hundreds of different types of neurons discovered and categorised for their unique attributes, but to simplify them to a manageable level, its common to place neurons into these three main categories:

Sensory Neurons

Functioning to receive external stimuli and send the notification onwards, such as your finger in contact with your mouse or phone.

Motor Neurons

Those that activate or deactivate a muscle movement. These are responsible for the stimulation of all your internally generated movement, both conscious and automatic.

Inter-neurons

Those communicating the notifications from one neuron to the next. Perhaps from a sensory neuron to a motor neuron to create an immediate reaction, or up to the neurons in your brain for more complex computation. These form a complex network throughout your entire body.

Special Note:

It should be recognised that these categories do not have hard boundaries. One notable neuron type discussed in biology circles frequently are Purkinje Cells of the Cerebellum. They were reportedly the first neuron cell to be discovered, and they play such a large role in the receiving of senses from the body and controlling how we move ourselves in response. Like many, they act to provide multiple types of function. [7] They also commonly studied due to their little variance between themselves, and a two-dimensional (-ish) structure type that is much simpler than many of their peers. [5]



How are neurons structured?

As neuron functions vary widely, so does structure. However, all follow the same trend in containing the following components:

  • Soma - aka. the cell body;

  • Axon - aka. the neurite;

  • Axon Terminals;

  • Dendrites;

  • Spines (aka. Dendrite Terminals).

Soma

This contains the nucleus and is where most of the neuron’s structures for renewal, growth and repair are produced. As per usual, within the nucleus is where most of the mitochondria is located which generates the ATP for the neuron to fuel its actions. (#powerhouse-of-the-cell) The cell body is also the site where incoming signals are summed, to determine if the threshold is reached to send its own signal.

Axon

This is the section of stretching from the cell body, to send a notification to the axon terminals. Almost every neuron has a single axon, however this has been shown not to be an absolute rule. [2] The axon is like a power cable that runs from the wall to your device (eg. Smartphone). The goal is to get power to the device, but because it wouldn’t be useful to have to connect directly to the wall, a cable is used to run the distance. In humans, an axon can be micrometres in length in the brain, or even run the full length from your spine to your toes. Axons running through your body will also get grouped together, which is what we call nerve bundles.

Axon terminal

Located at the tip of the axon, these terminals are the location from which the message is communicated from the neuron to its target. For motor neurons, the target cell would be a muscle tissue cell. For sensory, it would come from a receptor cell. For interneurons, the target would usually be to the other neuron’s dendrite terminals, but in some cases will also go to axons, axon terminals or the cell body.

Dendrites

Like the axon, dendrites extend out from the cell body, but with the different purpose of sending messages to the cell, rather than from. They are typically shorter than axons, but also greater in number, with few neurons only having one dendrite. [2]

Spines

Branching off the dendrites like little… well spines… these dendrite terminals are the reflection of the axon terminals. They receive signals which are then passed through the dendrites to reach the cell body for computation.

Others

Other notable features of many neurons are Myelin sheaths that an encase axons. Back to the power cable analogy, these myelin sheaths act as the plastic insulator surrounding the cable. This makes the speed of sending signals faster and results in less wastage of energy along the journey.

Finally, though not technically part of a neuron’s structure, its feels important to identify what is called the synapse.  The synapse is the junction point between sending and receiving terminals (eg. dendrite and axon terminals), which are referred to as synaptic terminals.


How do neurons work?

 Keeping it simple for today, this article will be talking broad picture inputs and outputs. But fear not! We’ll be sure to cover the technicalities of each stage in future reading.

Inputs:

Usually receiving its input via the dendrite terminals, the neuron can receive “excitatory” (which contribute to activating a response) or “inhibitory” inputs (contributing to preventing a response). However, the neuron can receive inputs to the cell body and axon also, which are commonly inhibitory types.

Logic:

At the base of the axon, where it meets the cell body is what we call the trigger zone. If the sum of the excitatory and inhibitory inputs meets the trigger requirement at this location, the trigger is pulled sending a notification (a type of electrical impulse called an action potential) down the axon length. Like a pass-fail exam, it doesn’t change the result if the calculated sum is much larger than it needs to be. The same signal is sent along the axon if it meets the minimum requirement.

Output:

When the axon terminals receive the notification sent from the trigger site (axon hillock), they then send their notification on to the target. As previously mentioned, the target could be another neuron, or could be a muscle cell to activate. This output could be an electrical charge or chemical. You may have even heard of many of the different types of chemicals released, being the well-loved neurotransmitters that we target in many of the nootropic stacks in the VitaKea store. These neurotransmitters will then bond to receptor sites (like a lock and key) of the targets input. We’ll cover these in more detail in the neurotransmitter article to come.

Some other interesting notes:

-      Until recently, it was thought that each neuron only controlled release of one type of neurotransmitter, but in fact, many neurons have multiple different types, and some require a threshold level of neuron fire rate to be released!

-       When other inputs directly interface with an axon or soma, they can work to encourage or block the axon terminals sending out the signal.

-       Not discussed is how some inputs can actually be modulatory, changing the behaviour of a terminal. This can be in multiple different ways, but one way is reducing the amount of excitation required to trigger.


Wrap up

Hopefully this introductory article has got your synapses fired up to continue exploring the functions of your own neuronal cells, and their ever-active role in communicating and events from one side of your body to the next. There’s definitely so much more to discuss on this topic, so don’t end the adventure here! Next up in the neuron basics series is our in-depth discussion on synapses and how they perform as the mechanism for the neurons input and outputs. We’ll be releasing it soon to keep your learning on a roll!

Related articles currently in the works:

  • The Neuron – Synapses.

  • The Neuron – Neurotransmitters at Play.

  • The Neuron - Creating the Action Potential.

  • The Neuron - On Myelin Sheaths.

  • The Neuron - A Historical Journey.

Another article on biohacking biology basics:

If your up for a good walk-through, Khan Academy also has a quality course on the nervous system here.


Got questions?

Want to recommend an article topic? Just want to spitball some thoughts? Hit me up at thomas@vitakea.co.nz 😊
I always keen for a yarn on anything biology, biohacking or personal optimisation. Together we can sharpen both our mental blades!

Key players in my current health regime include meditation, regular exercise (type depending on current fixation), early to bed, early to rise, packing in as many fungi & leafy greens as possible.
My
supplementation varies as I test out new protocols. That considered, I prioritise anything that can be utilised for long-term benefits. Of course, for special cases I can definitely appreciate a good stimulant, or perspective modifier.

 

 

 

 

 

 

 

 


Supplementary Reading

Want to drink straight from the source and to get REALLY in-depth and detailed on neuronal cells? Then brace yourself for fire hydrant rates of information and go check out some of the literature we used in the writing of this article:

[1] “Cognitive impairment 18 years before clinical diagnosis of Alzheimer disease dementia”, American Acedemy of Neurology, (2015).

[2] “Overview of Neuron Structure and Function”, Molecular Cell Biology - 4th Edition, (2000).

[3] “Neuronal Types”, Developmental Biology - 6th Edition (2000).

[4] ”Nerve Cells”, Neuroscience - 2nd Edition (2001).

[5] “Neuronal Cell Types”, Current Biology Volume 14, No. 13

[6] “The Human Brain in Numbers: A Linearly Scaled-up Primate Brain”, Frontiers in Human Neuroscience, Volume 3, No.31, (2009)

[7] “Purkinje Cells”, The Embryo Project Encyclopedia, (2014)

 


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