by Mol Smith 2010  

Anatomy at Mic-UK
Human Neurons

 

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Content: 

  Overview Single Neuron Dendrite / Dendron Axion Neural Network    
    Synapse Diagram Nucleus Schwann cell Neuro Transmitter    

 

  Mylin Sheath Motor Neuron Disease Quantum Engine?        
         Credits Links    
               

The Human Neuron Cell
Without doubt, the human brain is considered the most complex structure in the explored Universe. Over 100 billion cells compacted into a space no larger than a small melon, this organ is the seat of sophisticated awareness and a reality-modelling system second to none. It cannot be compared to a computer, even though many analogies are incorrectly made, because almost every single cell component is a unique processor plus memory device. Unlike computers, the brain continually readjusts its hardware: new physical connections are constantly being made as redundant ones are broken. The magic component in this truly outstanding achievement of evolution and nature is a cell called a Neuron.

Spelling: Neuron or Neurone?
The correct spelling in both American English and British English can be either Neuron or Neurone, although there is an increasingly modern tendency to consider the simpler alternative of two spellings for the same noun as the preferred one.

Unique Cell
Neurons in the brain (with one exception - in the hippo campus) cannot replicate themselves, and are therefore incapable of renewal, which makes the neuron unique when compared to all other cells in the human body. Neurons form a complex web (a network) with multi-flexible-connections achieved via tiny tentacle-like structures (dendrites), almost touching at their tips. The microscopic gap between any two connections is called a synaptic gap, and it is across this space, that tiny messenger chemicals travel to appropriate chemical receivers on dendrites at the far side. Processes which conduct impulses towards the main cell body are called Dendrons, and those which conduct impulses away from the cell body are called Axons. Different types of neurons (nerve cells) exist in the human body: , bipolar, psuedounipolar, and multipolar. These cells are future supported in the brain by Neuroglia, cells which are ten times more numerously packed around the neurons throughout the central nervous system. These are thought to be involved in memory processes and their function is to encode information in the form of RNA.

I have a used a single 3D model of a Neuron to create an artist's view of a section of a Neural Network composed of brain cells. This movie below represents a static section of the human brain, minus supporting tissues, chemicals, and blood vessels.



Please wait for movie to load!
For an 8 meg HQ version 600x600 - click here!

Now, let us take a closer look at a single Neuron. I have used a virtual 3D model to produce two cells below. They are the same cell but I have made one of them more transparent so you can look at the hidden processes inside.

You might wish to compare my model with the SEM image of a similar Neuron below, and then see the detailed diagram beneath it. Both these images are from Wiki and are used here under the collective commons licence. Please refer to wiki for reuse permissions.


The SEM image of a Neuron is produced here (above) under the Creative Commons Licence and is located at Wiki.
Please visit
http://commons.wikimedia.org/wiki/File:Neuron-SEM-2.png for reuse permissions






This image used from
http://en.wikipedia.org/wiki/File:Complete_neuron_cell_diagram_en.svg
Please follow link for further permissions of use.

I think one of the true miracles of the human brain is the fact that the Neuron uses both electrical and chemical processes to facilitate communication between cells. This ultimately produces human thought.

Information Processing - The Synapses
My movie below (made from using virtual 3D models) clearly shows how one Neuron communicates with another. An electrical signal travels along the Axon or Dendron to the Dendrites where chemical messaging molecules 'swim' across the synaptic gap to appropriate receiving pores on the other cell. The reception of the transmitter chemical triggers an electrical signal in the interconnecting cell. Some forms of mental ill health - notably, depressive illnesses - are thought to be caused by an imbalance or reduced quantity of one or more chemical transmitters (e.g. dopamine, serotonin).





For a higher quality movie (800x800) - please click here.

Neurons also exist throughout the human body and transmit signals to and from the brain at up to 200 mph. The axon is a long extension of a nerve cell, and takes information away from the cell body {A&D}. Bundles of these axons are what we commonly term 'nerves' when located away from the brain (Central Nervous System - CNS). Dendrites bring information to the cell body
{
B & C}. The Axon is insulated (like a copper stranded wire is with plastic) by a Myelin coating, except for periodic breaks called nodes of Ranvier, increasing transmission speed along the Axon. The Myelin is manufactured by Schwann's cells, and consists of 70-80% lipids (fat) and 20-30% protein. The cell body (soma) contains the neuron's nucleus (with DNA and typical nuclear organelles).

A typical neuron has about 1,000 to 10,000 synapses (that is, it communicates with 1,000-10,000 other neurons, muscle cells, glands, etc.). The complexity of such a network confounds our attempts to fully comprehend the staggering complexity and sheer sophistication of the human brain.

This exquisite schematic diagram below (
Public Domain from Wiki) reiterates the process very clearly.

A public domain image from Wiki please see
http://en.wikipedia.org/wiki/File:Chemical_synapse_schema_cropped.jpg
for reuse permissions


Before leaving our brief look at the Neuron, I would like to inspire you with another image and some personal observations - not so scientific, but interesting theoretically none-the-less. Here is a conceptualised network of neurons in the human brain. We may well think of the brain (mind) a bit like a Turin Machine (computer), where information comes in through a variety of physical senses, is mapped and compared with previous information, and then used to activate an external response (run, shout,) or make a decision, or even just determine another perspective about our external world. Nothing comes out which isn't already 'put-in' in the first place. But this idea may not be entirely true! Roger Penrose, a distinguished UK mathematician and associate of Stephen Hawking, believes micro (nano) organelles may exist in the brain which allow information in a general sense to enter the system from the quantum world of sub-atomic particles and energy packets. This was put forward in one of his book's -
The Emperor's New Mind and I would recommend reading this work if you believe the mind/brain is no more than a very sophisticated computer.




Disease
Diseases of the Brain or CNS are explored in the Anatomy of the Brain. However, one disease which typically targets the neurons of the human brain is Motor Neuron Disease *wiki

Motor Neuron Disease is a set of conditions which affect motor neurons *wiki and normally mainfest symptoms in people aged 50 to 70 years. The outcome is progressive muscle wasting, weakness, muscle fasciculations, spasticity or stiffness in the arms and legs, and overactive tendon reflexes. Patients may have slurred speech or other less common symptoms. Every muscle group in the body requires both upper and lower motor neurons to function, therefore any malfunction in the neurons controlling any muscle group, will manifest difficulties in those areas and often will culminate in progressive loss of function.


Prognosis
Most cases progress quite quickly with patients declining rapidly over several months and suffering increasing motor disjunction at the disease spreads to other areas of the brain. Motor Neuron Disease is normally fatal within 25 years with about half of patients dying within just over the first year from diagnosis. Those who do not succumb within the first year to 15 months, may survive up to 10 years with 1 in 5 patients surviving for 5 years, and 1 in 10 patients surviving 10 years.

     
     

Links

Motor Neuron Disease Association
Patient co.    more on MND
Neurons at Wiki
National Society Epilepsy


Credits
Anatomy 3D model data and .obj files from Anatomium
Information derived from collating and proving data from a variety of sources on the internet and from anatomy books offline.
Where indicated, all image and video content is copyright - mol smith - www.microscopy-uk.org.uk
Images which are not copyright are public domain or creative commons licence and are marked as such.



Comments or requests for expansion of this article should be made to the author: mol smith
     

 

 

 


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