Neuroscience is the study of the brain and nervous system. The general overview here will give you a basic understanding of how mental health interventions affect your thoughts and emotions. It’s not as simple as implied by common phrases such as “chemical imbalances” or “you don’t have enough serotonin.” Knowing this, you’ll be better able to contribute to your care and treatment plan. Otherwise, you’re more likely to make treatment decisions based on emotion instead of logic. Don’t worry. We’re not talking PhD material here. We’ll keep this as painless as possible.
Your brain consists of nerve cells called neurons, each connected to other neurons, creating a network like that shown in Figure 3. Well, it’s a bit bigger. In reality, your brain has upwards of 80 billion neurons, each with up to 1,500 connections to other neurons.
Your brain constantly sends signals over this network, from one neuron to the next. When these signals reach different parts of your brain, they cause things to happen, e.g,. your left foot moves forward. Every thought, feeling, sensation, or memory is a result of signals sent between neurons.
Your brain continuously creates new connections between neurons. It also creates new neurons, though not as often as it makes new connections. When you learn, your brain is making these new connections.
Your entire personality, behaviour, and consciousness emerges based on the entire pattern of connections between the billions of neurons in your brain. It’s similar to how a complex computer program emerges when millions of 1s and 0s are placed in the right order.
Neurons receive signals from other neurons. Based on the signals it receives, each neuron turns on or off like a switch. When it’s on, it sends signals to the neurons it is connected to. When it’s off, no signals are sent. Each neuron contains a part to receive signals, a part that (among other things) decides whether to turn itself on or off, and a part that transmits signals. This is conceptually illustrated in Figure 4.
Pretend you’re a neuron. How do you decide whether to turn on or off? The first thing to know is that there are two basic types of signals, excitatory (on) and inhibitory (off). At any given time, some of the hundreds of neurons connected to you have sent you an excitatory signal, some an inhibitory signal, and some no signal at all.
If you receive more excitatory signals than inhibitory signals, you’ll be on. If there are more inhibitory signals, you’ll be off. This process is called summation (think of every excitatory signal as a +1, every inhibitory signal as a -1, and add them up; if the sum is more than 0, the neuron is on).
If you are on, you transmit signals to all the neurons you’re connected to. Other neurons are connected to different neurons than you are and receive signals from them. Each neuron reacts differently than every other neuron because it has a unique set of connections.
So far, we’ve treated neurons as if they were nice compact shapes, where the transmitting part of one is connected to the receiving part of another as if they’re wired together. The two kinds of signals are like two different strength electrical currents. That’s not exactly true.
For starters, neurons aren’t compact, simple shapes. Instead, they look more like the gangly structure shown in Figure 5. Signals are received from other neurons by dendrites. The cell body processes the signals as we just described. Any outgoing signals are sent along the axon, where they are passed from an axon terminal to the dendrites of another neuron.
Second, neurons aren’t physically connected to one another. There’s a small space, called a synapse, between the axon terminal of one and the dendrites of another. To transmit a signal, a neuron must bridge that synapse. It does this by releasing chemicals, called neurotransmitters, that drift around in the synapse, as shown in Figure 6.
Across the synapse and attached to the dendrite, there are objects called receptors. When a neurotransmitter drifts close to a receptor, the receptor grabs it and holds on. While it’s holding the neurotransmitter, the signal has been sent (it now registers as +1 or -1 to the receiving neuron).
The axon of each neuron stores neurotransmitters to be released when the neuron is on. They are stored in sacs called vesicles. Releasing the neurotransmitters is like opening a door between a vesicle and the synapse.
Neurons also create neurotransmitters in the first place, from smaller building blocks called precursors. These are either brought in from outside the neuron or are byproducts of other things going on in the neuron.
There are more than 100 types of neurotransmitters, both excitatory and inhibitory. The most important ones affecting mental health are serotonin, norepinephrine, dopamine, and gamma-aminobutyric acid (GABA).
Just as there are different neurotransmitters, there are different receptors. Each accepts only one type of neurotransmitter. Usually, there are several types of receptors for each neurotransmitter. The dendrites of a neuron can have many receptors (all the same or of different types).
What happens to a neurotransmitter after it is grabbed by a receptor? The receptor holds onto it for some length of time (dependent on the type of receptor) and then releases it back into the synapse.
Receptors grab neurotransmitters only when they drift close by. There’s no guarantee a neurotransmitter will find a receptor. But the more neurotransmitters in the synapse, the more likely a receptor will grab one.
Neurotransmitters don’t drift around the synapse forever. If they did, signals would keep being sent over and over. Three things happen to reduce the number of neurotransmitters in the synapse. First, they can drift away from the synapse, to be absorbed by other cells in the nervous system. They can be broken down by enzymes. Finally, they can be reabsorbed by the axon, called reuptake. This makes them available to be released again in the future.
Armed with your newfound knowledge of neuroscience, you may be asking: how is this related to mental health treatments? Here’s a quick preview.
We started off saying that feelings (and everything else) are a result of signals travelling between neurons. To greatly simplify, the greater the number of signals sent through the network by, for example, the neurotransmitter serotonin, the happier we feel. More signals mean that more serotonin receptors are activated. The more the merrier, literally!
Treatments take advantage of this by doing one or more of these things:
Ensuring enough serotonin or its precursors (i.e., nutrients) are available. Signals can’t be steadily sent if you’re deficient. However, boosting beyond normal levels won’t help. Neurons will only create, store, and release as much serotonin as they need.
Stimulating the axon to release more neurotransmitters when activated. This is akin to opening the vesicle door wider. The more neurotransmitters in the synapse, the more likely they’ll find a receptor.
Adding another chemical that looks like serotonin into the synapse. This tricks receptors into grabbing it and activating as if it were serotonin.
Slowing the reuptake of serotonin from the synapse back into the axon, so more remains in the synapse longer.
Different treatments can affect serotonin and other neurotransmitters via different mechanisms. If two treatments use the same mechanisms to affect the same neurotransmitters, they’ll give similar results. That’s true even if one is a pharmaceutical and another is a natural supplement.
Thoughts, emotions and behaviours emerge from signals sent between neurons. Neurons are either on, at which time they send signals, or off. Changes in the connections between neurons occur with learning.
Signals are sent by neurotransmitters such as serotonin, norepinephrine, dopamine, and GABA through the synapse between neurons and grabbed by receptors. These determine if the neuron is on or off.
Treatments affect whether neurotransmitters are successfully sent across the synapse. They can change the number of neurotransmitters available, change how long they remain in the synapse, or block receptors.
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