Neurotransmitters all serve a different purpose in the brain and body. Although there are several different minor and major neurotransmitters, we will focus on these major six: acetylcholine, dopamine, norepinephrine, serotonin, gamma-aminobutyric acid (more commonly referred to as GABA), and glutamate.
Acetylcholine (ACh) is found throughout the nervous system. It is the only neurotransmitter that sends and receives information between the motor neurons and voluntary muscles (muscles you have conscious control over, such as the biceps). This means that every move you make depends on the release of ACh from your motor neurons to your muscles to make the move. Some examples include: walking, talking, typing, and even breathing. This neurotransmitter found throughout the body is also distributed often in the brain. In addition to motor, ACh also contributes to attention, arousal, and memory.
Dopamine (DA) is one of the three most common neurotransmitters found to regulate many different aspects of behaviour, along with norepinephrine and serotonin. DA is used by neurons to make voluntary movements and movements in response to emotion. It also plays a role in the brain’s reward system to help reinforce certain behaviour that result in pleasure/reward. For example, it is due to a surge of DA that prompts us to take that second slice of pizza!
DA is also found to be a crucial factor for providing focus and memory consolidation.
Norepinephrine (NE) is another neurotransmitter found to regulate behaviour. NE contributes to the modulation of mood and arousal, and is commonly referred to as the stress hormone. When you are in a stressful situation it is NE that is spread all over the body to prepare for the situation. A few examples are as followed: NE increases the amount of oxygen to your brain to allow you to think clearer and faster, NE increases your heart rate to allow more blood to rush to your muscles when you need them, and NE also shuts down metabolic processes for the time of the stressful event so blood and energy that would normally go to the digestive organs can focus on other parts of the body. Scientists refer to this event as ‘Fight or Flight’. Fight or flight is when our body uses NE to prepare us to stay and work through the stressful situation (fight) or run from it (flight).
Serotonin is the last of the three most common neurotransmitters found to regulate behaviour. Serotonin is found to affect/regulate a number of different functions in the body/brain from digestion to mood. The release of serotonin from neurons appear to play a predominant role in the regulation of sleep, wakefulness, and eating behaviours.
GABA and Glutamate
GABA is known as an inhibitory postsynaptic potential (PSP) -- meaning it decreases the likelihood the neuron will fire an action potential. In contrast, glutamate is known as an excitatory PSP -- meaning it increases the likelihood the neuron will fire an action potential. It is due to the firing of an action potential that allows the neuron to open and release the neurotransmitters to carry the messages on. Many of the neurotransmitters such as NE and ACh are versatile as they can produce both inhibitory or excitatory PSPs. GABA and glutamate are different as they exclusively produce one or the other.
GABA and glutamate are the brain’s most plentiful neurotransmitters, with GABA present in approximately 40% of all synapses in the brain and glutamate in over 50%! It may seem odd, but it is very important to have inhibitory PSPs -- it is because of GABA we can stay calm and not overwhelm ourselves. When we get overwhelmed it compromises other processes in our body, such as our ability to think clearly, have an appetite, or sleep. As you can imagine in contrast, it is also crucial to have excitatory PSPs. Glutamate is the neurotransmitter best known for contributing to learning and memory.