16.26 System: Neural System- The Brain  
     
  Nothing is more tantalisingly close yet so far as understanding the human brain.  
  This 6.6 kg organ stores over 100 trillion (100,000,000,000,000) bits of information over the course of 70 years, equal to 500,000 sets of the Encyclopaedia Britannica.
  
  85% of the brain is made up of water. It also receives 20% of the bodies blood supply. A fully formed human brain contains around 100 billion neurons, or nerve cells as opposed to the worm that has 23. The brain is an amazingly sensitive area of the body. A stroke can occur when the brain increases temperature by only 4 degrees Celsius.
  
  The packaging of the cortex of the human is in the same proportion of almost any other animals brain. The point is it is larger in size. Humans have only about 1.25 as many neurons per cubic cm as chimpanzees.
  
  There are approximately 146,000 neurons per cubic millimetre of cortical surface. The human brain has an area of about 1,400 cubic centimetres and about 70 billion neurons. A further 30 to 40 billion neurons are tightly packed in the primordial brain the cerebellum.
  
  The chimpanzee and the gorilla have brains of about 500 cubic centimetres and with about 6 billion neurons. The chimpanzee brain is around 12 million neurons per cubic centimetre. Humans have around 20.6 million neurons per cubic centimetre.
  
  Important understandings of neurons and memory from previous chapters
 
  Before we look at a way of understanding the key systems of the brain, it is important to recap on the points we discussed regarding neurons in chapter 12.
  
  (1) For neurons to work, there must be hormones.
Hormones get the system going and are responsible for neurotransmitter
release (determining how many neurons fire).
  
  (2) The process for neurons is always Hormones triggers (a) electrical
pulse (memory) and (b) release of neurotransmitters.
  
  (3) Learning and memory will always be subject to the level and type
of hormones presently exciting the neurons
  
  Logically making sense of the brain
  
  As we have done in other chapters, let us look at what specialist areas we would expect in the human brain given the specific tasks that involve existing as a human:
  
  Sensory processing centres
We would logically expect to see areas of neurons responsible for
processing sensory input. We would logically expect eyesight to
have the largest required region of neurons, with the other senses in
varying proportiong.		  
  Motor processing and command centres
Motor processing neurons are the neurons that control the movement
of the body as a whole, or part. You would logically expect a large
area controlling motor processing and command centres to ensure
that the human is capable of remembering and co-ordinating movement.
  
  Glands (Hormones) and Neuron managers
In contact with sensory and motor processing centres you would expect
a large part of the brain to have neurons in control of glands as well
as the production of neurotransmitters (small chemical equivelents).		  
  That hormones are the vital link as to how neurons communicate to the
rest of the body as well as the production of neuro transmitters, you
would expect this segment of the brain to be tightly packed and probably
the oldest part. 		 
  You would also expect that the glands and neuron managers are linked
as well as having some ultimate chain of command.
  
  Memory neurons
Finally, you expect to see memory neurons- neurons specialised
for storing information that might be important for future survival.
Because these are secondary to the immediate survival of the human,
you would expect these to be furthest “away” from the fundamental
structures.		  
  As it turns out, this is exactly how the brain is structured. What is often described as the primordial brain (the glands, neuron command centre, sensory and motor processing centres) are the essential survival systems, while the “modern” brain is the more recent expansion of the neo-cortex (memory cells that are on top).
  
  The Limbic System (Primordial Brain)  
  The Limbic System is essentially the base of the Brain. It is the section closest to the brain stem (the neurons connected to the spinal column) and is the principal control centre for the automatic creation of hormones and neurotransmitters for the rest of the body and brain.
  
  The body produces basically two families of hormones and neurotransmitters:
• Positive, stimulus
• Negative, depress		  
  That is not to say that all positive stimulus to the body might be classed as a positive emotion. The amygdala, an almond-size knot of neuron cells located close to the brain stem, specialises in memories of fear.
 
  At the centre of the Limbic system (the tip of the brain stem) is the Thalamus- (a tight bunch of neurons that in real life looks like the end of a circumcised penis!). The thalamus is where all senses (except taste and smell) are routed into a “common sense”. This is important as its allows the Limbic system to consider a macro position of the state of affairs and put into action an appropriate hormonal response.
  
  The left hemisphere of the cortex  
  Above the Limbic System is the Cerebral Cortex (principally memory). The Cortex is divided into two parts- left and right hemisphere. The left side of the cerebral cortex controls the right side of the body. The left hemisphere controls the smaller muscle groups such as fingers. The left hemisphere controls the face muscles.
  
  The left hemisphere also controls language and logical activities- things that happen in specific order.
  
  The right hemisphere of the cortex
  
  The right side controls the left side of the body. The right hemisphere controls the larger muscle groups associated with running, and moving the arms, such as fighting or fleeing. It directs spacial, simultaneous things- which happen all at once- and artistic activities. These differences could be explained when our ancestors began to make and use symbols (language and art).
  
  How big is the brain’s capacity?  
  A contemporary view is that the brain contains up to 100 billion neurons. We now know that microtubules are the centre of action in terms of electrons and 01001 etc information storage. An average Neuron may have up to 6 Mb of Microtubules (and up to 3Mb) of parallel connections between MicroTubules.
Therefore, on a rough estimate, the information storage capacity of a human brain could be as high as 6Mb x 100 Billion Neurons. This is a significantly higher figure than has been previously considered.
 
  However, what is most interesting is the parallel processing capacity of a human brain (say up to 3Mb of connections per Neuron x 100 Billion Neurons x 20 connections per neuron). In other words, the greater strength of the human brain is not necessarily information storage ( even though it is immense), it is solving complex problems.
  
  In terms of the capacity of the brain in terms of absorbing information at 100 trillion over a lifetime (100 terrabytes in computer terms) of around 70 years, or around 25,550 days which equals around a intake capacity of around 3.9138 gigabytes of new information per day.
 
  Speed of impulses into the brain
  
  Tests on the retina and brain activity detect electric impulses from the retina along the optic nerves to the cerebral cortex at a few milliseconds.
  
     
 
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