Blog 4: Consciousness and Brain Physiology 101 – Part 1: The Electron Power of the Brain

This week, we will begin by looking, in a very simplified way, at what powers the brain and maintains consciousness and memories. 

For sure, the brain is a very metabolic ‘high maintenance’ organ: it is only about one fiftieth of the weight (approximately 1.4kg) of the entire average body weight (around 62 kg), but it uses 60% of our body’s glucose requirement, and 20% of our daily calories. The brain is protected by an exclusion zone (the membranes of the blood-brain barrier) which control what enters and leaves its tissues.  Glucose molecules are the only energy source that can penetrate this barrier to provide the energy needed to maintain the vital ‘electrical activity’ of our brain neurons.

Blood Glucose and Oxygen

The oxygen molecules needed to release energy from glucose during cell respiration also cross the membrane and reach a specialized part of the cell (an organelle), the mitochondria, which ‘recharges’ the cell’s ‘batteries.’

The carbon dioxide, water and heat produced during respiration that occurs in the presence of oxygen (aerobic respiration) moves out of the brain tissue across the blood-brain barrier to the veins carrying blood away from the brain.

It is the maintenance of the approximately 100 billion brain neurons, and the production of brain waves and consciousness, that requires such a large fraction of the body’s metabolic resources.

Executive Summary.

The key to understanding brain’s electricity is that it involves the movement of charged particles. It is helpful to think of these movements in three movements.

  1. Energy Generation. The movements of two charged subatomic particles (the electron (e-) and the proton (P+ – a hydrogen atom nucleus) recharges the brains ‘batteries’ (ATP molecules).

Surprisingly, both particles arrived from space aboard meteorites /asteroids and reached your body directly or indirectly from green plants.

  1. The Movement of Ions Across Neuron Cell Membranes: The generated energy is used in turn to power the movement of charged ‘atoms ‘(ions  atoms that have gained or lost one or more electrons – mainly Na+, K+, Ca2+ and Cl).  The movement of these ions produces the nerve impulse (the action potential).                                                
  2. Generation of Brain Waves /Consciousness. Physicists have discovered that accelerating and decelerating particles emit electromagnetic waves.  One theory is that it is the interaction of these waves in specialized parts of the brain (neuronal correlates of consciousness (NCC)) that produces consciousness.

The rather surprising conclusion as we will review in this blog and next week’s blog is that the brain is powered by high energy electrons.  To understand the ultimate source of these electrons, we will need to travel back billions of years and delve down into the sub-microscopic world of the bacterial and plant cell.

The History of a Glucose Molecule.

Before our time travel, let’s have a look the origins of the different types of atoms in  glucose and oxygen molecules which are so essential for our brain.

The atoms in the following molecular formula shown in blue are ultimately derived from water, while those shown in red came from carbon dioxide.

Glucose Atom Origins

 

Executive Summary.

The key to understanding brain physiology – electricity is that it involves the movement of charged particles. It is helpful to think of these movements in three movements.

  1. Energy Generation. The movements of two charged subatomic particles (the electron (e-) and the proton (P+ – a hydrogen atom nucleus) recharges the brains ‘batteries’ (ATP molecules.

Surprisingly, both particles arrived from space aboard meteorites /asteroids and reached your body directly or indirectly from green plants.

  1. The Movement of Ions Across Neuron Cell Membranes: The generated energy is used in turn to power the movement of charged ‘atoms ‘(ions  atoms that have gained or lost one or more electrons – mainly Na+, K+, Ca2+ and Cl).  The movement of these ions produces the nerve impulse (the action potential).                                                   
  2. Generation of Brain Waves /Consciousness. Physicists have discovered that accelerating and decelerating particles emit electromagnetic waves.  One theory is that it is the interaction of these waves in specialized parts of the brain (neuronal correlates of consciousness (NCC)) that produces consciousness.

The rather surprising conclusion as we will review in this blog and next week’s blog is that the brain is powered by high energy electrons.  To understand the ultimate source of these electrons, we will need to travel back billions of years and delve down into the sub-microscopic world of the bacterial and plant cell.

Key Geological and Biological Events that Allowed Life and Consciousness to Evolve.

Key Event 1:  The Formation of the Earth’s Continents and Oceans.                                   (4 Billion Years Ago)

I have a polished egg-shaped paperweight on my desk, a memento of my visit to see the impressive stromatolite (stromatolith) marbles laid out there like a giant stone carpet in Lester Park, near Saratoga, New York State.

Lester Park Stromos

My stone egg is composed of fossilized bacteria-like plants (cyanobacteria) dating back half a billion years to the Cambrian period when the rocks which are now under New York were at the bottom of a shallow, tropical sea south of the equator.

Stromatolite Egg

The primitive life forms petrified in my paper weight when the earth was already four billion years old.  During this vast time span, the earth’s originally molten rocks cooled to form the planet’s solid surface.  Where did the water that formed our planet’s sea come from?  Uncertainty still surrounds the scientific answer for this key question. The original theory was that water escaped (degassed) from the cooling rocks to form steam clouds in the very hot early atmosphere.  After further cooling of the earth, the oxygen-less (anaerobic) atmosphere cooled, clouds formed, and the first rains fell to form the first proto-oceans. 

A more recent theory that is now gaining widespread acceptance, however, is that the water in our present day oceans and our bodies arrived from space via water-rich asteroids/or meteorites.

Water Asteroids

The main evidence for this more recent theory is that the types of hydrogen (the isotope ratio)  in asteroid water is almost identical to that of earth water.  The falling asteroids and carbonaceous meteorites also delivered a surprisingly complex cocktail of organic molecules, including amino acids and polyols (organic substances closely related to sugars such as glucose).. The first building blocks for the first life forms that evolved in the ‘primeval soup’ of the ancestral earth may have come from outer space.

At the time when the ancient life forms in paper lived, the numerous volcanoes their environment was spewed out rivers of molten larva and, more importantly for our story, the vast quantities of carbon dioxide gas that provided the carbon and oxygen atoms in the glucose molecules needed by our brain neurons.

Ancient volcanoes

These events which occurred eons before the primitive life in my paperweight lived provided the water and carbon dioxide required for modern life, but what about the oxygen that must move into the brain along with glucose molecules?  To understand the origin of the oxygen that we breathe we need to take a closer look at the primitive bacteria-like plants fossilized in my paper weight.

Key Event 2:  The Formation of Phospholipid Molecules – the Membrane Builders

A key event that occurred in the primeval ‘biotic soup’ more than three billion years ago was the combination of phosphorus with lipids (fat-like molecules) to form phospholipids.

Phospholipid Bilayer

In water, phospholipids form a two-layered (bilayer) structure that isolates two different regions  prevents water-soluble compounds passing through the membrane from the  ‘outside’ to the ‘inside’.  In water, the bilayer forms a spherical structure, a liposome that encloses a central ‘watery’ region.  As we will see, proteins that pass through the membrane from one side to the other are responsible for the movement of most substances into, and out of cells.

Liposome

It is suggested that the formation of large liposomes was an important step in the formation of the first primitive cells. The membranes form a similar role to the ‘walls’ in a house – the outer membrane protecting the cell controlling what enters the cell.  The membranes inside the cell divide the cytoplasm into numerous room-like compartments which have different contents and functions.

Key Event 3:  The Formation of the First Cells. (Around 3.5 Billion Years Ago)

The development of membranes allowed the first primitive prokaryotes – bacteria-like cells that lacked a nucleus, to develop. These organisms used to be called the blue-green algae.  The colour description was accurate, but they should not be called algae.  The cells of algae are usually larger, more complex, and contain a nucleus.  The blue-green bacteria (cyanobacteria) are the most primitive form of life on earth.  Early species of cyanobacteria produced the stromatolite marble like my paperweight from Lester Park.

Cyanobacteria                                                    Chains of Cyanobacteria Cells.

The dividing cells stick together of form long chains. The cell membrane is protected by a thicker ‘cell wall’ whose outer surface is a ‘sticky’ mucus-like slime coat. Particles of sand and other debris stick to outer layer. For reasons we will discuss in the next section, in sunlight, the cynobacterial cells absorb carbon dioxide with the result that the sea water around them becomes less acid. 

The more alkaline conditions produced encourage calcium carbonate to precipitate out of the sea water  – their growing crystals attaching to the trapped particles. Gradually, the cells produce the stone-like stromatolite formation. 

Stromatolites are rare today due to completion with more advanced forms of plant life.  Shark Bay in western Australia is one of the few places where the mushroom-like stromatolites flourish in the highly saline sea water. 

Living Stromatolites

Key Event 4:  The Evolution of a Water-Splitting Enzyme and Photosynthesis.

One of the most important events in our story is the appearance of a manganese-containing protein that acts as an enzyme capable of splitting water and releasing the oxygen needed by our brain neurons.

Two water molecules attach to the enzyme in the ‘water splitting’ complex containing a cluster of four manganese atoms of a protein photosynthetic pigment. These proteins are attached to membranous liposome-like sacs (thylakoids) in the cytoplasm.  The flattened thylakoid sacs are rather like small liposomes within the large liposome of the cell membrane surrounding the cell.

Cyanobacteria Thylokoids

The complex splits two water molecules to form four hydrogen ions (protons H+), two electrons and a molecule of water.  As we will see in the final section of this blog, hydrogen ions and electrons allow the cell to store energy until it is needed to perform biochemical  ‘work’.

EM Structure of a Cyanobacterium

The first stromatolites seemed to have formed around 3.5 billion years ago. Gradually, their photosynthetic activity over one billion years released oxygen into the air changing the atmosphere from anaerobic to aerobic – the type of atmosphere we can breathe today.  Initially the oxygen built up was painfully slow since the vast iron deposits of the earth had to ‘rust’ and be converted into red iron oxide.  The red bands in the following section through a stromatolite are due to the red oxide produced when oxygen released from stromatolites (lower bands) oxidised elemental iron to iron oxide.

Stromo Red Banding

The high energy hydrogen ions and electrons are used to reduce (add hydrogen) to the carbon dioxide that the Cynanobacteria removes from the surrounding water to form carbohydrates such as glucose and starch.  These products of photosynthesis store energy which can be used later by brain neurons to maintain their ‘electrical’ activity.

Key Event 5:  The Formation of Organelles and Complex (Eukaryote) Cells. (0.5 Billion Year Ago)

The final event we will review occurred at the beginning of the Cambrian around half-a-billion years ago.  The Cambrian period showed an explosion of more complex multicellular organisms that doomed the stromatolites to virtual extinction from the high point of their evolution 2.7 billion years ago.

As we noted, the first primitive bacteria-like cells lacked a nucleus and neither did they have other complex membrane-bound structures in their cytoplasm.  Once oxygen became available in the atmosphere, a new form of respiration, aerobic respiration, which was much more efficient at extracting energy from food  (animals) or the stored products of photosynthesis (plants).

The key point here is the relatively new theory of endosymbiosis that is best explained by a simple diagram:

Endosymbiosis

Where did the nucleus of the more advanced animal and plant cell come from?  As suggested by our diagram (A), an ancestral blue-green bacteria may have engulfed another type of bacteria  (an archaebacterium) that then lived in partnership with the original cell and specialized in organizing the activities and division of the cell.  

It is suggested that a type of cyanobacteria was engulfed to form the chloroplasts (B), the photosynthetic unit of higher plants. 

A third proposed example (C) is a type of purple, non-sulphur bacteria entered the cell and evolved into the mitochondria of animal and plant cells – the organelle responsible for releasing energy in cells.

If this theory is correct, the neuron can be viewed not just as a network of analogue computers but also as a collection of different life forms living and working together for their mutual benefit.

Our story so far has explored the origins of the carbon, oxygen and hydrogen atoms in the glucose and oxygen molecules needed by our brains  to release energy from glucose.  In the blog next week, we will discuss how the electron power derived from the plants via food glucose molecules is used to generate energy in our brain neurons.