The Application of Metabolic Pathways on Biotechnology
The Crossover to Another Dimension: Drugs
What are Drugs?
A drug is a naturally grown or chemically synthesized substance that when taken has the ability to alter the body and mind either physically or psychologically.
The Jewel of the Human Body: The Brain
To understand how exactly various drugs affect the neurological pathways of the human brain, it is important to grasp an understanding of what the brain is and how it functions.
Image Citation
The brain is composed of more than 100 billion nerve cells or neurons. These billions of interconnected neurons allow the brain to transmit messages in the form of electrical signals, and allow different areas of the brain to communicate with each other.
Beginning the process of nerve cell communication, a stimulus is received in through the dendrites, creating arousal within the cell. The continous buildup of arousal will cause the cell to pass through a certain threshold. Reaching this threshold will cause the cell to snap out of its "resting period". The cell has now "turned on" and will begin to rapidly fire electrical impulses causing the charge of the cell to change and the action potential to trigger.
* The action potential either triggers or doesn't trigger - there is no half way point. This is referred to as the "all or nothing principle".
The illustrated nerve cell is currently in its "resting period". During this period, the positively charged Potassium ions surround the outside of the cell, while the negative Sodium ions fill the inside.
Once the cell has triggered, the electrical impulse stored in the soma, will shoot down the axon and reach the axon terminal. At this point, the impulse will cross the synapse in the form of a neurotransmitter, and enter the receiving neuron. This process concludes by returning the nerve cell back to its "resting period".
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The Alteration of Pathways By Drugs!
How exactly does this alternation, proposed by drugs, occur? To begin the explanation simply, when drugs are taken in they rapidly induce changes on the brain's synapses. Obtaining access to the brain's reward pathways gives the user their usual sense of "high".
Dendrites
Dendrites
Dendrites
Dendrites
Dendrites
Dendrites
Click on the images of above to learn more about major drug categories and their dramatic effects on the neural pathways!
Origin of the Reward Pathway
The discovery of the Reward Pathway in the brain was made in the 1950's through a series of experiments involving rats. In the experiment, a group of rats were trained to press on a lever that would deliver a small electrical jolt directly to a region of the brain known as the Nucleus Accumbens This jolt would deliver a sense of "pleasure" to the rat, causing them to continously press on the lever in order to achieve the same euphoria despite feelings of physical discomfort.
Likewise, when the jolt was delivered to the area of the brain outside of the Nucleus Accumbens, the rats would fail to continously press on the lever.
These experiments allowed scientists to determine that the main neurotransmitter in this process was Dopamine. These experiments also led scientists to name this "pleasure center" of the brain - Reward Pathways.
To begin, the reward pathway in the brain creates feelings of pleasure when we engage in pleasurable activites: excercise, eating, sex, etc. These activities create pleasure because when they occur, they cause increased levels of Dopamine to be produced.
That being said, why do drugs create such a dramatic addiction? Drugs are designed with the intent to create extenteded pleasure to the human body. When taken they begin to interrupt and stimulate neural communication within the brain, creating and overstimulation of Dopamine. To counter this overstimulation, the brain begins to dramatically reduce the number of cells that once dealt with the control of Dopamine, thus leading the user to a sense of "high" and "euphoria".
Interesting Fact
Did you know that drugs release approximately 2 - 10 times more Dopamine within the Reward Pathways of the brain that natural rewards such as eating do?