Neurons, Neural Networks and Neural Pathways.

In the last tutorial, we had a look at the nervous system and its basic function. We covered the Central Nervous System and the Peripheral Nervous System and explored how they interact with each other by sending messages between the brain and the body’s organs or muscles.




 
Now we can explore how these messages are actually sent and received. Understanding this is critical to understanding how nicotine affects the brain and how it leads to the chronic brain disease, addiction.

If you were to look at brain tissue under a very powerful microscope, you would see it consists of billions of tiny cells that reach out and touch each other. These cells are called neurons. (Nerve cells.)

Clusters of neurons that connect to each other can be referred to as biological neural networks, with different networks connecting to each other by neural pathways.

In this tutorial, we will break down this information step by step, but before we do this, lets have a look at what such a microscopic image looks like.

Neurons

Neurons viewed under a microscope. Image made available by http://brainmaps.org/ and used under Wikipedia Creative Commons Licence.

The Neuron.

The neuron is a cellular structure that processes information both electronically and chemically. Neurons are typically categorized into three different classes. Motor Neurons, Sensory Neurons and Inter-Neurons.

Motor Neurons.

These neurons exist in the Central Nervous System and typically control muscles throughout the body.

Sensory Neurons.

These neurons are typically stimulated by physical mediums such as light, sound and touch. They send information back to the Central Nervous System, where it can be processed by the brain.

Inter-Neurons.

These neurons make up the majority of neurons in the brain. They are neurons that connect to other neurons. Inter-neurons are what we will typically  be referring to from here onwards.

A Neuron’s Basic Anatomy.

The basic structure of a neuron can be broken down into the following elements:

SOMA

The main cell body containing its nucleus which assists in maintaining the cells structure.

DENDRITE

A dendrite extends from the soma and receives information from other neurons. Multiple dendrites branch out from the main cell body and form what is typically referred to as Dendritic Tree.

AXON

The axon is a cable like structure that extends from the soma and connects to the dendrites of other neurons. Information is passed down the axon electronically to the Axon Terminal.

AXON TERMINAL

The axon terminal is where the axon branches out and forms a connection to the dendrites of another neuron, via something referred to as a synapse.

SYNAPSE

A structure where chemicals, referred to as neurotransmitters, are transferred to receptors on another neuron’s dendrite, and bind.

RECEPTOR

Receptors are molecular “keyholes” that exist on a neurons’ dendrites, they bind with chemicals (Neurotransmitters) that have been passed to it from other neurons.

The Anatomy of a Neuron

The image above illustrates the basic anatomy of a neuron and the direction information travels from the dendrites to the synapse, where information is then transferred to another neuron.

 

Neural Networks and Neural Pathways.

The brain consists of billions of connected neurons, forming neural networks. These networks, process and control information flow.

They allow you to feel and interact with the physical world around you. They allow you to feel emotions such as anger and euphoria, or sensations such as hunger and thirst. They also allow you to form memories and learn new skills.

Neural Network

Neurons connect to each other and form neural networks.

 

Whenever you see an image, for example, a yellow flower, the information is carried from the eye via neural pathways that link to multiple neural networks.

One of those networks would hold information that helps you to identify and describe the color as yellow. Another network would hold information that allows you to identify the shape as a flower.

At some point, a pathway is triggered by you identifying the flower and the information is sent to a network containing specific memories of that flower.

Those memories might trigger another pathway that leads to the reward centre of your brain, which in turn release chemicals that make you feel good. You don’t just see a flower, you see a beautiful one!

Neural Networks

View the You Tube clip below for an animated example.

 

 

So there you have it, a very basic overview of the nervous system and hopefully a greater understanding of its neurons, neural networks and neural pathways. Now we are ready to discover how nicotine hijacks your nervous system and how it leads to addiction.

Next Tutorial.

The Short and Long Term Effects of Nicotine on the Brain.

Previous Tutorial.

An Introduction to Your Nervous System.

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Comments

  1. Dear Mr. Kellett:
    I am writing to request permission to reprint the image “basic anatomy of a neuron”. I have also sent a message to your email address.
    We would like to use the figure in a report chapter being written by a committee for the Institute of Medicine, National Academy of Sciences. The final report is scheduled to be published his summer by the National Academies Press.

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