Alcohol, Caffeine, Nicotine.... What is the commonality? There are all drugs - legal drugs. Most humans have tried these drugs through coffee, alcohol, or cigarettes, which are things that are extremely addictive. So, what is a drug, and how does it work that makes it hard for a human to quit?
What is a drug?
A drug is a chemical substance that changes an organism's physiology or psychology when consumed. As the drugs could affect the structure or function of the body, they were intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease. However, since most drugs, such as heroines, cause harm to our bodies, they are illegal. To be a legal drug, it should pass a complex procedure to prove that the drug is safe to use.
Types of drugs
Drugs can be classified into 4 different types: Opioids, Stimulants, Depressants, and Hallucinogens.
Opioids: opioid is a drug derived from the source of opium, the poppy plant. It is usually to moderate and recover severe pains by sealing off the receptors that trigger the sensation. Opioids can also be used for the removal of heavy sedation and provide euphoria.
Stimulants: stimulants are used to treat ADHD and narcolepsy by providing an advanced central nervous system operating capacity. The most well-known stimulant is caffeine, which increases focus and wakefulness.
Depressants: depressants inhibit the central nervous system that prohibits the process of information. This makes people reduce intrusive thoughts and deliver a sense of relaxation.
Hallucinogens: Hallucinogens change how we perceive the environment around us by affecting change of color, sound, movement, and time. This drug can even lead to an out-of-body experience. Examples of this type of drug are psilocybin, LSD, or mescaline.
How does it work?
Drugs interact with receptors on the cell's surface or enzymes, which interfere with the signals that the neurons send, receive, or process via neurotransmitters. Drugs bind to the receptor site and mimic proteins as drugs have similar chemical structures to the natural neurotransmitter in our body. This action can block the protein's physiological function and lead to an abnormal message sent or the release of an atypical amount of natural neurotransmitters that disrupt regular communication between neurons.
There are two ways that drugs bind to the receptor: Agonist and Antagonist.
Agonist: the drugs that bind to the target receptor site where the protein should be and respond to the neuron. Examples of drugs that do this binding are morphine, nicotine, phenylephrine, and isoproterenol.
Antagonist: the drugs that bind to the target receptor site but have no reaction with it. It reduces the action of an agonist at the receptor site involved. An example of a drug with this type is propranolol.
Where does the drug affect?
Most drugs affect the important part of the brain that controls life-sustaining function such as blood pressure, respiration, heart rate, and body temperature by slowing down or speeding up the central nervous system. Mainly, three sites of the brain are affected by the drugs: Basal Ganglia, Extended Amygdala, and Prefrontal Cortex.
Basal Ganglia: The site where it provides the human positive forms of motivation, like eating or socializing. It is the part where the brain’s “reward circuit'' (brain structures that control and regulate our ability to feel pleasure) is created.
Because drugs keep providing pleasure to the brain, the circuit realizes the presence of the drug, which makes it hard to feel pleasure without the drug.
Extended Amygdala: The site where it controls stressful feelings such as anxiety, irritability, and unease. The drug led this site to feel discomfort without the drugs, and the more humans find the drug, the more sensitive the circuit becomes, which makes it hard for humans to quit addiction to the drug.
Prefrontal Cortex: The site provides the ability to think, plan, solve problems, make decisions, and exert self-control over impulses. This drug makes this part malfunction, which encourages humans to use more drugs. Teens are more vulnerable to drugs because the prefrontal cortex is the part of the brain where it matures at last.
The process of the drug movement
So, how does the drug come in and release from the body? There are 4 steps included: Absorption, Distribution, Metabolism, and Elimination.
Absorption
The drugs are absorbed into the bloodstream in the body. The speed of the absorption depends on the type of the drugs - normally between one to six hours. The drug molecules in the bloodstream shift from where it was injected or enter to the desired site for metabolism or excretion, such as the liver, kidney, or lungs, by binding to the plasma proteins in the bloodstream. To move to the target site, the drug molecule should cross the walls of blood capillaries. Subsequently, except for the brain and spinal cord, a region where it only allows extremely high lipid-soluble drug molecules, the drug molecules spread throughout the body.
Distribution
The drug will simply circulate through the body and be distributed to different organs or the brain through the bloodstream. In this process, the drug will affect the chemicals and receptors of the cell, which affects the body.
Metabolism
In this stage, the body breaks down the drug molecules into smaller and simpler molecules so that they will be much easier to eliminate from the body. The well-known organ for this process is the liver. Enzymes in the endoplasmic reticulum in the liver catalyze the metabolism process. In order to catalyze this process, there are lots of reactions occurring, including oxidation, reduction, addition/removal of chemical groups, or splitting of chemical bonds. Some drug molecules may affect the body in this stage.
Elimination
Metabolized drugs release from the body, usually through urine or face.
The main route of excretion is through urine, the kidney; the gaseous or volatile drug molecules are eliminated by the lungs. A small amount of molecules is through sweat, saliva, or breast milk.
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