The Nervous System
Methamphetamine is dangerous for many reasons; however, one of the most damaging effects of meth is on the brain, specifically, on neurons and neurotransmitters. This consequently alters the efficiency of the rest of the nervous system, further damaging the body. This page is dedicated to exploring the specific biological chemicals that are effected by meth and how the regular fuctions of the body are changed by the presence of the drug in the nervous system.
In a normal nervous system, electrical signals are received and sent through the use of cells called neurons. The arrival of the signal at the end of the neuron triggers the release of chemicals, specifically neurotransmitters, into a gap between the end of one neuron (presynaptic) and the beginning of the next neuron (postsynaptic). This gap is called the synapse (Brooker, 2011). Neurotransmitters are released into the synapse and then bind to receptors located on the post-synaptic neuron (ibid). The binding of the neurotransmitter to the receptor triggers a response in the neuron. After this, the neurotransmitters left in the synapse are reabsorbed by the pre-synaptic neuron. This stops the post-synaptic neuron from being further triggered (ibid).
When methamphetamine is introduced to the nervous system, neurotransmitters are unable to be reabsorbed into the pre-synaptic neuron. This is because meth blocks the passages through which the chemicals are taken up through. This causes neurotransmitters to flood the synapse and continually trigger responses in the post-synaptic neuron. Meth affects 4 neurotransmitters in specific: dopamine, serotonin, epinephrine, and norepinephrine (Limpy, 1999).
Dopamine is the neurotransmitter responsible for feelings of pleasure, pain, and several other emotional responses (Erickson, 2012). A greater amount of the chemical causes sensations of pleasure and happiness, while a smaller concentration can have the opposite effect, causing the individual to feel pained or saddened. Dopamine is also responsible for movement (ibid). Too much dopamine can cause the individual to experience uncontrollable, repetitive movements and twitching, as often seen in meth addicts. Too little prevents movement, as in the cause of those with Parkinson’s disease. An increased amount of dopamine can also trigger bizarre hallucinations and delusions, causing the user to display similar psychological characteristics as individuals with schizophrenia. For example, meth users claim to see “bugs” beneath their skin, leading them to scratch and tear and their skin (Meth Project, 2012).
Methamphetamines not only block the reuptake of dopamine into the pre-synaptic cleft, but also cause the neurons to secrete more dopamine than normal – causing the synapse to become extremely flooded with the neurotransmitter. This flooding continually triggers the post-synaptic neuron, which creates the high sensation that users experience (Limpy, 2011).
Because meth causes dopamine to be secreted from the neurons, the amount of dopamine available is depleted significantly, and eventually drops below the necessary amount once the user begins to experience a crash. This causes the individual to have difficulty moving and display drastic mood swings (Meth Project, 2012).
Serotonin is the neurotransmitter responsible for sleep, appetite, mood, aggressive behavior, and sexual desire . An increase in serotonin allows for the individual to be less tired, less hungry, and more aggressive. High amounts of serotonin also heightens libido (news-medical.net). These characteristics can be observed in those who use methamphetamine, as such users display less tiredness and decreased appetite. This causes extreme weight loss in users and allows them to remain awake for long periods of time. Other characteristics include an increase in aggressive behavior and sexual desire (Limpy, 1999).
The presence of meth on serotonin, like dopamine, blocks the reuptake of the neurotransmitter – flooding the synapse. However, unlike dopamine, meth does not cause serotonin to be secreted by neurons into the synapse. Eventually, once the user begins to crash, the amount of serotonin drops below average, causing tiredness, hunger, and mood fluctuations(Meth Project, 2012).
Epinephrine is more commonly known as adrenaline and has the ability to increase heart rate, blood pressure, as well as to dilate air passages. Epinephrine is also responsible for ‘fight-or-flight’ response (Limpy, 1999).
Like in serotonin, meth blocks the reuptake of epinephrine into the pre-synaptic cleft, causing the user to experience a faster heart rate and blood pressure (Meth Project, 2012). This can eventually lead to devastating effects on the cardiovascular system (see Cardiovascular System).
Norepinephrine, similar in molecular make-up to epinephrine, is also responsible for stimulating respiration and increase blood pressure and heart rate. Norepinephrine also controls attentiveness, learning, and mood (Limpy, 1999).
Meth, like serotonin and epinephrine, blocks the reuptake of norepinephrine into the pre-synaptic neuron, causing the effects of norepinephrine to be heightened (ibid). For example, during a meth high, users experience increased breathing, heart rate, and blood pressure. However, once the user begins to crash the individual has a greater difficulty learning, as the ability to ‘pay attention’ has been impaired. Furthermore, the user experiences drastic mood swings.
(Meth Project, 2012).
As mentioned earlier, meth inhibits the efficient functioning of dopamine, serotonin, norepinephrine, and epinephrine pathways; however, methamphetamine also damages the neuron itself, further negatively impacting the nervous system (Limpy, 1999). Neuron death not only affects the release of these specific neurotransmitters, but other neurotransmitters as well, making it difficult for the nervous system to send and receive signals. This can cause the user to experience difficulty in learning, memory, paying attention, controlled movement, regular emotions, and making rational decisions (Meth Project, 2012). Once damaged, the neurons cannot be fully replaced, altering the biochemistry of the brain and nervous system all together (Meth Project, 2012).
The image to the left depicts the sections of each brain that meth impacts. In short, meth begins damaging the neurons of the nervous system even at first use. It is for this reason that methamphetamine is considered one of the most dangerous illicit drugs.