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.
| Image # 16 – Sodium potassium gate – depolarization action potential to produce electrical current – shows sodium entering the cell |
| Image # 17 – The energy transformation cycle |
| Energy Production Automobile vs the Human Body | ||
| • Categories | Automobile | Human Body |
| • Energy Source | Gasoline | Glucose, Proteins and Fats |
| • Fuel Intake System | Gasoline Tank | GI Track or Intravenous |
| • Oxygen for Combustion | Carburetor/air filter | Respiratory System |
| • Combustion System | Engine | Cell Body – Mitochondria |
| • Energy Production | Electricity/Current | Electricity/Current |
| • Energy Storage | Battery | Adenosine Triphosphate (ATP) |
| • Energy Utilization | Turn on ignition | Turn on Ion Pump System (cell membrane) |
| • Result | Starts Automobile | Open Ion Gates (sodium, calcium, chloride, etc.) |
| • First Message | Electrical/Current | Electrical/current |
| • Energy Transformation | Convert to Mechanical | Electrical to Chemical to Mechanical |
| • Mechanical end point | Movement of Gears | Movement of a body or perform body function |
This electrical gradient is then propagated down along the second part of the nerve cell called the axon.
I know this is getting challenging, but stay with me…
The Axon
The second major part of the nerve cell is the axon, which extends from the cell body (like electrical wires) and end in branches called nerve terminals. The axon has 360-degree insulation along its length like in electrical wires. The insulation system around nerve cells is called the myelin sheath. In the brain, the myelin sheath is created by a supporting cell called the oligodendrocyte. The myelin sheath is divided into small regions, and the junction between each region is known as the node of Ranvier.
In the spinal cord, the myelin sheath is produced by a cell called the Schwann cell, and each Schwann cell serves one region of individual axon insulation. Electrical currents created by the process of depolarization jump or travel the axon from one node of Ranvier to another. This form of jumping electrical currents (messenger) along the axon is called “salutatory conduction” and allows nerves to conduct currents at a faster rate than if the current had flown directly through the axon. Current flowing directly through the axon will experience more resistance, causing the current or electrical messages to decay and slow down. In conditions such as multiple sclerosis, the myelin sheath is damaged, and this causes a slowing of electrical conduction.
| Image # 18 – Saltatory Conduction with node of Ranvier and Schwann cell |
So, let us summarize this first messenger system that the cell utilizes to send messages.
It all starts in the cell body with the utilization of an energy source.
Table # 12 – Energy and the Messenger System
| Cell Body | Creation and propagation of the first messenger | Description |
| Chemical energy source | Glucose, protein, fats | From nutritional intake (GI and IV) to bloodstream |
| Oxygen source | Respiratory system | Lungs and bloodstream |
| Combustion system | Mitochondria | Energy source and oxygen combust to create energy. |
| Chemical energy storage | Adenosine triphosphate (ATP) | Supply of energy to the cell membrane and pump system |
| Pump system | Open ion gates – sodium-potassium, calcium, chloride, or other systems | Utilize ATP as a chemical energy source |
| Create electrical energy | Ions move in and out of cell membrane, causing an electrical gradient in the internal and external environment of the Cell. | Depolarization of the membrane begins – this is the propagation of electrical impulse or energy from the cell body to the axon. |
| Axon – second part of the cell | Propagation of electrical impulse – the myelin sheath with its node of Ranvier allows for rapid saltatory conduction. | To the axon terminal |
| Electrical current created | The gradient between two regions of the cell membrane | Causes the current to start moving from one part of the cell along the Axon |
| Saltatory electrical current | Flow of current along the axon, jumping from one node of Ranvier to the next | Electrical messenger flowing outside the cell down the axon to the axon terminal-- Axon terminal – third part of the cell |
A Second Messenger System of the Cell
Another messenger system that exists in the nerve cell is the neurochemical messenger system, which gets its order from the core of the cell (the nucleus), also located in the cell body. This system starts with an instruction system referred to as DNA. DNA contains all the instructions for the productions of many neurochemicals in the nervous system. Like electric currents, neurochemicals are classified as messengers. Neurotransmitters are created in the cell body based on instructions from DNA. These chemical messengers or neurochemicals are also called neurotransmitter substances, as they truly transmit messages.
They are produced in a precursor state in the cell body. Precursor neurotransmitters are neurotransmitters in their non-active state. By the time they get out of the cell body and are transmitted to the axon terminals (endpoint) through the axon, they transform from the precursor neurotransmitters to full-fledged neurotransmitters.