The nervous system is made up of the central and peripheral nervous system. While the central nervous system is made up of the brain and spinal cord, the peripheral system is made up of the sensory and motor neurons that connect the central system to the rest of the body. In our discussion of drugs and their effects on neurons and neurotransmitters, we will focus on the peripheral nervous system. Neurons are interconnected cells that supports out body’s information system; it is made up of dendrites, the cell body, the axon, and the terminal branches. The dendrites of a neuron receive the information from other neurons, which travels to the axon from the cell body (soma). The axon speeds the information through the neuron, which ultimately reach the terminal branches. The terminal branches then proceed to transmit the messages to other neurons through their respective dendrites. If the input to a neuron’s dendrites is strong enough, the cell “fires” or transmits the message through an action potential- a brief electrical charge that travels down the axon of the neuron and is generated by movement of charged ions in the axon’s membrane. This voltage is responsible for sending information from one neuron (presynaptic neuron) to another neuron (postsynaptic neuron). (Below is a link of a picture of a neuron and the direction of the action potential).
The message is transmitted between two neurons (the presynaptic neuron and the postsynaptic neuron) in a region called the synapse- a junction between the axon tip and the dendrite. When the information travels from the axon to the terminal branch, the message is contained in neurotransmitters that are carried in vesicles. These neurotransmitters travel from the pre synapse of a neuron to the post synapse of another neuron. The neurotransmitters bind to the receptors of the post synapse and then the postsynaptic neuron can carry the information. Neurotransmitters’ effects are heavily influenced by drugs which could enhance or reduce the effect of a certain neurotransmitter. While agonists enhance the effect of a neurotransmitter, antagonists reduce the effect of the neurotransmitter.
Over this past summer of shadowing my pediatrician, I met a patient who had been suffering with a post-traumatic stress disorder. This patient had decreased levels of appetite, depression, and severe anxiety. My doctor sent the individual to a psychiatrist for further help. When my doctor and I saw the patient after a two-month follow-up, we observed that the patient had regained more appetite and had been feeling less depressed and had less anxiety. The patient had been sleeping better with no awakenings in the middle of the night and had also been eating at least two to three meals a day instead of none to one meal a day. We learned from the patient that the psychiatrist had prescribed Prozac. Reflecting upon this now, serotonin is a neurotransmitter that regulates mood, but also plays a role in regulating sleep, appetite, and digestion, among other physiological processes. It is usually taken up by the presynaptic neuron and reused later or broken down. This patient may have had decreased levels of serotonin, resulting in less receptors bound to serotonin. However, the patient began improving with Prozac which is known to be a selective serotonin re-uptake inhibitor. Instead of being taken up the neuron, the neurotransmitter is bound to a receptor for a longer period by Prozac, increasing the effect it has. Consequently, one would expect that mood, among other physiological processes, would improve based on the enhanced effect of serotonin. Prozac is most commonly prescribed to treat depression and plays a major role in enhancing the effect of serotonin.
Links:
https://courses.lumenlearning.com/wm-biology1/chapter/reading-types-of-signals/
https://www.healthline.com/health/serotonin-deficiency