5 high-yield neurotransmitters you need to know before test day. #mcat #mcatprep #premed

Added: 2026-05-17

[00:00:00]I scored a 132 on the bio-biochem section of the MCAT, and here are five neurotransmitters that I would know before you take the exam. Number one is glutamate, and yes, this is also an amino acid. This is the major excitatory neurotransmitter within the central nervous system, the brain, and the spinal cord, which basically means that it tends to activate stuff like neurons.

[00:00:14]It does this by binding a bunch of different types of channels, which usually results in the movement of sodium and calcium positive charge into the cell. Now, besides just being generally excitable, this neurotransmitter is very important for learning and memory in a process called long-term potentiation. Excessively high levels of glutamate signaling are implicated in seizure disorders, whereas very low levels of glutamate can be implicated in things like sedation and coma. The second neurotransmitter is actually GABA, which is derived directly from glutamate. And this is actually the main inhibitory neurotransmitter within the central nervous system. In other words, it basically shuts down stuff and stops neurons from firing. Now, the way that GABA does this is by actually activating chloride receptors, which allow chloride, which is a negatively charged ion, to enter the cell and hyperpolarize it, making it less excitable. Low levels of GABA can result in uninterrupted glutamate activity and potentially seizure disorders, whereas very high levels of GABA can result in sedation and coma. Notably, important medications such as benzodiazepines, and barbiturates, and alcohol all activate GABA receptors, so they cause sedation.

[00:00:58]At very high doses, this can of course also result in very low respiratory drive and possibly death. The third neurotransmitter is acetylcholine. This neurotransmitter, first of all, causes skeletal muscle contraction. It's also the major neurotransmitter of the parasympathetic motor nervous system, and it is implicated in learning and memory in the brain. Low levels of acetylcholine in the brain are implicated in development of Alzheimer's disease, and blocking acetylcholine release through such things as the botulinum toxin can actually result in paralysis. When it comes to causing skeletal muscle contractions, acetylcholine works by actually activating sodium ion channels, which results in sodium moving into the cell and causing depolarization. At number four, we have dopamine. This is an interesting neurotransmitter which also acts as a hormone and is produced both in the brain and in the adrenal medulla, and it is a catecholamine like norepinephrine and epinephrine. Now, in the central nervous system, dopamine is involved in several processes such as motivation, reward, and pleasure. It's also involved in regulating movements.

[00:01:38]In the brain, we need to know three regions where it is produced. The first is called the mesolimbic pathway, sometimes called the mesolimbic rewards pathway, and this is where dopamine is implicated in reward and development of addiction. The second area is called the nigrostriatal pathway, and this pathway is involved in regulation of movement, where dopamine is the main neurotransmitter. And lastly, there is the tuberoinfundibular pathway. Now, this is the connection between the hypothalamus and the anterior pituitary gland. And here, dopamine is actually called prolactin inhibiting hormone. So, here it's acting as a hormone released by the hypothalamus. And as that name suggests, it basically shuts down release of prolactin from the anterior pituitary gland. And finally, small amounts of dopamine are produced in the adrenal medulla. Now, high levels of dopamine in the brain are associated with psychotic disorders such as schizophrenia, whereas low levels of dopamine are associated with development of movement disorders such as Parkinson's disease. And the last neurotransmitter is serotonin. This is both a hormone and a neurotransmitter in the brain, and it is derived from the amino acid tryptophan. Now, within the brain, serotonin is used in complex processes such as regulation of mood, emotional regulation, sleep, and appetite. And in the CNS, serotonin is primarily produced in the brainstem at something called the nucleus of raphe.

[00:02:30]Now, it's important you know that low levels of serotonin are thought to cause depression. And first-line treatment of depression are medications called selective serotonin reuptake inhibitors, which literally prevent neurons from taking back up neurotransmitter serotonin, which results in more serotonin remaining in the synaptic cleft and signaling for a longer period of time, which basically increases the amount of serotonin signaling in the brain. And for some patients, that's very effective. Also, please sign up for my free live workshops, which I host every Thursday at 8:00 p.m. EST, 5:00 p.m. PST, where I walk through MCAT strategy and practice passages. If you're interested, drop the word workshop in the comments or DM us and we'll send you information