Neurotransmitters and their effects, basically!

General they are present in only a very small amount in the body, according to this textbook I'm using, "try detecting a pinch of salt in an Olympic swimming pool" to get an idea of how much is in brain tissue.

acetylcholine the 1st neurotransmitter discovered and found in all motor neurons. It stimulates the muscles to contract, including the heart and stomach's, it's even involved in the action of blinking.

dopamine involved in movement, attention, learning, and pleasurable or rewarding sensations. evidence suggests that the ability to increase dopamine activity in the brain (cocaine's and nicotine's) is linked to the addictiveness of many drugs.

serotonin + norepinephrine one's involved in sleep, mood, emotional state, and the other is involved in the activation of cells to gear up under threat or danger. norepinephrine might also be involved in learning and memory retrieval.

GABA (gamma-aminobutyric acid) found primarily in the brain, inhibitory to other neurons, helping to balance and offset other excitatory messages (alcohol makes people feel relaxed and less inhibited partly by increasing GABA activity, which reduces brain activity).

endorphins in 1973, researchers discovered receptor sites in the brain that are specific to a group of painkilling drugs called opiates (morphine, heroin, codein... all derived from the opium poppy). Apparently, because it has a plug-in, the conclusion was that the brain manufactures its own morphine-like chemicals that act as neurotransmitters. In a few years, they were identified, and deemed collectively, as "endorphines" (endogenous morphines). Chemically similar to morphine, endorphins are 100x more potent. Endorphins are released in response to stress or trauma and reduce the perception of pain.