Читать книгу Concussion - Kester J Nedd DO - Страница 27
ОглавлениеON A METAPHYSICAL level, from the smallest to the largest, the hierarchy of brain functions starts at the subatomic, atomic, and molecular levels and manifests in the histologic and macro levels of nervous system structures. The macro level represents the structural anatomic organization required to achieve functional activities that we can see. The chemical activities and reactions that occur in each nerve cell and their supporting cells ultimately produce electrical currents and neurochemicals. These electrical currents and neurochemicals serve as messages, and how such messages are promulgated between various systems is what makes us behave in very complex ways.
In the field of quantum physics, we think of mechanical activities such as the movement of an arm or a car or a planet spinning on its axis as an expression of mechanical energy. Energy is not something we can see or touch, but we can experience it in the world around us. Nothing exists without energy. All mechanical energy that makes things move in the universe must come from somewhere. Our universe also operates on the principle of moving from one form of energy to another, and we humans at our core do the same.
Consider an automobile. Before we can move a car, we need the mechanical structure of the engine (the cell in humans) that converts chemical energy (gasoline in cars, glucose in humans) to electrical current, some of which are often stored in the battery.
This electrical energy stored in the battery is needed to turn on the switch to start a car.
This form of electrical energy is ultimately converted to mechanical energy that turns the gears and the wheels to get the car moving.
So, we go from energy tied up in a chemical (glucose in humans or gasoline in cars) to the electrical energy (electrical current in the nerves) that is produced from the chemical source.
We then finally go from the electrical to the mechanical part of the energy, where there is movement of the gears in case of the car or arms in case of the body. That is the mechanical part of the equation.
Energy produced in whatever form in the universe is what makes things happen. This entire transformation of our systems from one form of energy to the other is the basis for the working of our nervous system. Thus, energy for all systems in the universe is the key messenger that carries the instructions that guide us through our existence. One does not have to be a physicist to understand that this is truly the metaphysical part of our human existence.
The Neuron
Cellular organization at the histological and neurophysiological level is central to the messaging elements of the nervous system. The key cells in the nervous system where most of the activity is going on are the nerve cells or neurons. As the engine, neurons or nerve cells are responsible for the combustion to produce energy for the transmission of all messages.
As an engine, each nerve cell or neuron has components or characteristics that make its function as an energy producer. Not only does the neuron produce energy, but it also transforms energy from one form to the other. Here is how a neuron is structurally organized to function in energy production and transformation:
The first part of the nerve cell involved in the quanta physical process (energy manufacturing and transformation) is called the cell body. This is where the action starts.
| Image # 12 – Nerve Cell (neuron) – Cell Body |
Table # 11 -- The anatomy of a neuron
| Components of the Neuron | Description |
| Cell Body or Soma | Contains the cytoplasm and nucleus, with the chromosomes or genetic material. Makes up the Grey matter mostly |
| Axon | Wire-like structure with insulation that extends from the cell body and contains filaments that carry neurotransmitters (neurochemicals) from the cell body to the end or axon terminals |
| Schwan cell with Myelin Sheet | Cell around the axon that produce insulation know a myelin sheet. This makes up the white matter of the brain and spinal cord |
| Node of Ranvier | Space between each Schwan cell |
| Axon or Nerve Terminal | Terminal ending of the axon that connects to another nerve cell |
| Dendrite | Extensions from the cell body and connects to the axon terminal of an adjacent cell |
| Synaptic Bouton | The end of an axon terminal |
| Synapse | The point where two nerves connect. Nerve or axon terminal bouton connects to dendrite. |
Functions of a Neuron based upon the anatomy
Cell body: The cell body is where the metabolic activity in the cell occurs to produce, store, transform, and utilize energy. The cell bodies of many nerve cells congregate in specific anatomic locations in the central nervous system. When they congregate on the surface of the brain together with their supporting cells, they are known as grey matter. When the cell bodies congregate deeper in the brain, such as in the basal ganglia, they are called ganglia. In the brain stem and spinal cord, the congregation of cell bodies is called nucleus (single) or nuclei (pleural). Like the outer peel of an orange, (the crown of the brain), the grey matter is the outermost layer of the cerebral cortex. The grey matter is where most of the cell bodies of neurons, their interconnections and their supporting cells are gathered. There are multiple layers of cells making up the grey matter, and populations of neurons are arranged in the different layers to communicate with each other and produce energy or electrical currents in a synchronous manner. The structured layering of the cell bodies has an arrangement that allows for functional connections between layers of cells near and far. The one hundred billion neurons that make one thousand trillion connections have an order in which they are structurally and physiologically arranged, which, once disrupted, can change a human.
| Image # 13 – Cerebral cortex – grey matter neuronal cell bodies and their connections |
The cell bodies of neurons, residing in the gray matter, use chemical reactions to create electrical currents that serve as the messages that direct us. This is where most of the head behavior or sophisticated processing of the nervous system originates. These unique anatomic organizations are responsible for our memory, ability to process and sequence events, experience joy, sadness, anger, see things in three dimensions, and perceive space and time.
Furthermore, due to the fact that electrical activities originate in this cortical mantle (the peel of the orange), lesions (abnormality or scar) in the grey matter can cause seizures. Seizures are excessive electrical activities that are unregulated and cause an excess of electrical currents to be transmitted to the rest of the body. You can recall that in Mario’s case, he had a grand mal seizure in the period immediately following his accident. Well, during the process of his second trauma, there was an injury to the grey matter. This is the reason he had what has come to be known as “early post-traumatic seizure.”
Within the body of each nerve cell lies an energy-producing element called the mitochondria. The mitochondria is the real engine chamber of the cell where combustion occurs. Inhaled oxygen is distributed from the lungs to every living cell through the bloodstream. Energy is produced from the combustion (burning) of oxygen with products (energy sources) such as glucose, proteins, and fats that we ingest.
Once produced, this energy is stored as Adenosine Triphosphate (ATP), a chemical battery system in the cell. ATP works as an energy source to help various pump systems in the cell work. The pump systems are what induces the cell to produce currents that act as messengers. There are various pump systems in the cell, and they are located in the wall (cell membrane) surrounding each cell.
So, what actually causes the creation of the electrical currents? It is the movement of certain ions (such as sodium, potassium, calcium, magnesium) that are pumped through the gated channels in the cell membrane. This pump system utilizes the energy created by the mitochondria and extracts this energy stored in ATP.
| Image # 14 – Sodium Potassium Channel Resting membrane before depolarization |
The ion pump system in the cell wall or membrane – how does it work?
The various pump systems serve to transport certain elements known as ions in and out of the cell through various gated systems.
The cell membrane possesses multiple channels that are gated (have gates). To open and close these “ion gates” to permit certain ions to enter and leave, the gates are fueled by energy from ATP through various pump systems, and thus, ions can pass through the gated channels. Each gated channel can accommodate different ions, and in the mammalian brain approximately 12 ion channels have been identified (Wilson 1999).
Depending on the ion passing through certain types of gated channels, the stimulation or inhibition of electrical impulses can occur to produce less or inhibit the production of electrical impulses in turn. The amount of stimulation or inhibition also depends upon the amount and extent of the movement of certain ions in and out of the cell membrane.
Think of using the energy stored in the ATP battery system to open and close the gate of the channels for ions such as sodium, potassium, calcium, or chloride to pass in and out of the cell.
| Image # 15 – The sodium potassium pump system during depolarization creating an action potential |
For a moment, let us focus on one of the vital gated and pumping systems of the cell. Located in the wall of cells (cell membrane), this is the sodium-potassium pump. This pump is responsible for opening the doors to the sodium-potassium gated channel to allow sodium to enter from the outside, while potassium moves from inside to outside. When this gated channel is open, sodium moves freely into the cell and potassium moves out. With this movement of the two ions (sodium and potassium) across the cell membrane, an electrical gradient or differential is created. An electrical gradient is usually created across the cell membrane when ions move in and out, which implies there is a difference in the electrical charges inside and outside of the cell. This also depends on the concentration of ions inside and outside the cell.
The electrical gradient at a specific point in the membrane will be different from another in the nerve cell, and that creates a current which then prorogates this gradient along the cell, as the next point attempts to have a charge similar to the previous point. When the ions create an electrical gradient that in turn produces a current, a process known as depolarization or activation of the cell membrane is caused electrically. As the current flows to new areas in the cell, it caused more gated channels to open along the path of the current, thus creating more gradients as the current flows.
