Central Nervous System: A Case Study

If it were not for our central nervous system we would not know the smell of a flower or the warmth of the sun. We would not be able to pull our hand away from hot surface or run from danger. The central nervous system is what allows us to experience our senses and react after analyzing a variety of signals. These signals are carried throughout our bodies by specialized cells called neurons which relay the messages to each other. Some of these signals are passed along electrically, while others use a chemical signal called a neurotransmitter in the process of synaptic transmission or neurotransmission.

During neurotransmission a neuron before the synaptic cleft releases the chemical signal and it binds to specific receptors on the neuron after the cleft causing activation. After the desired outcome the neurotransmitters must be deactivated via reuptake, certain enzymes, diffusion, or glial cells. Reuptake occurs when the chemical is gathered in the axon terminal it was released from to prevent receptor binding. Enzymatic degradation is the process in which enzymes are used to trump the effects of the

neurotransmitter. The enzyme manipulates the properties of the neurotransmitter, making it unrecognizable by its receptors. Diffusion simply causes the chemicals to float out of the synapse away from receptors. Finally, a specific type of glial cells called astrocytes physically take the neurotransmitters away from the synaptic cleft.
It is because of neurotransmission and the release of serotonin that we feel good after exercising. Drug use also encourages neurotransmission and that is why people often feel a sense of euphoria upon using drugs. However, prolonged use of drugs can interfere with the normal functioning of neurons and these chemical messengers by imitating them, causing their activation, or preventing the activation of others. Most substances accomplish this by preventing the normal deactivation or reuptake of the neurotransmitter after it has been released in the synaptic cleft, prolonging its effects.
Drug abuse most often disrupts our pleasure seeking neural pathway that uses the neurotransmitter dopamine.

In the example of cocaine use, the drug binds to transporters meant to remove dopamine from the synapse, leaving dopamine without an exit strategy. Amphetamines such as methamphetamine also raise the amount of dopamine left over in the synapse. However, in this case it happens because the drug resembles actual dopamine and hitches a ride into the pre-synaptic neuron on its dopamine transporters. The drug then forces the dopamine out into the cleft. Drugs such as MDMA and LSD have an effect on the neurotransmitter serotonin. This special chemical signal helps to regulate our mood, circadian rhythm, sexual needs and hunger. MDMA also works by preventing reuptake. These are just a few of the countless drugs and neurotransmitters effected by their

use.
After the effects of drugs wear off the process of neurotransmission is allowed to return to normal functioning. However, when an individual abuses drugs for long periods of time it causes long-term changes to the process. Usually the first to occur is drug tolerance when the pre-synaptic neuron decreases production and the amount of the chemical signal released into the cleft. Tolerance may also cause the post-synaptic neuron to retract a number of its receptors. The body may even adapt by producing more specific receptors. Animal studies have shown that drug abuse can also encourage an increase in protein synthesis that leads to abnormalities in cell structure and function. Some substances act as poison to nerve cells and constant drug use damages parts of the cell impairing functioning. Research shows that the damage done by drug abuse and addiction can cause problems with memory, the thinking process, and motor control.
When an individual is successful in their endeavor of quitting some of the body’s physiology slowly returns to normal, while other changes are more permanent. Combating addition proves to be a difficult task because of the dependence the body now has for the substance. As the levels of dopamine rise due to drug use, over time the brain reacts by decreasing natural production of dopamine and receptors. Therefore, after an individual stops using they may have abnormally low levels of dopamine, causing them to feel pleasure less often. Treatment for addiction begin with a detoxification of the body by slowing and eventually stopping drug use that often causes cravings and withdrawal symptoms. Withdrawals can include physical symptoms such as profuse sweating, tremors, intense hunger, depression, and seizures or cognitive effects such as disorientation, racing thoughts and hallucinations. Some addictions such as those to alcohol, nicotine, and opioids have medications that may help. Medications may also be helpful in reducing the effects of withdrawals. Professional counseling or support groups may also be effective in convincing a person to stop abusing drugs.
Neurotransmitters are essential to the communication process between our neurons that carry important information to our brain to be interpreted. These chemical messengers are carefully regulated by the different mechanisms of deactivation and reuptake. Drug abuse causes these mechanisms to malfunction and allow for artificial fluctuations in the levels of neurotransmitters. If these imbalanced go uncorrected the normal functioning of our central nervous system and all of the aspects of our physiology it regulates will be compromised. Prevention and intervention are crucial for drug addicts if normal physiology is to be maintained.