Neurotransmitters are the key to how our brain thinks, feels and acts. Zoomed in, they act as a kind of variable switch between two neurons, allowing a signal to pass through or not. The biological chemicals that we as neurotransmitters use are repurposed hormones. A deficit in availability, or oversupply of any one of these neurotransmitters is the root cause of the majority of mental ill health and can be a cause of many other conditions not considered to be Mental Health.

Understanding Neurons and Neurotransmitters

Neurotransmitters are biological chemicals, generally hormones, that also serve the purpose of temporarily connecting one neuron to another to send a signal. This connection is very fast and last only a brief amount of time, triggering up to hundreds of times a second. The Neurotransmitter is effectively a kind of switch that either by its presence allows the signal through, or by its absence, doesn’t.

Of course, it is far more complicated than that. What follows explains, still fairly simplistically, how that works.

How Neurons Talk

A neuron is a cell in your brain that makes decisions. It receives signals from up to 20 thousand other neurons, then it makes a decision. That decision may be to do nothing, or send a signal to tens or thousands of other neurons.

In a similar way to modern electronics, each neuron has a particular set of calculations it can do, and in combination, that can do lots of interesting things. In modern electronics, we have certain kinds of logic circuits called “Logic Gates”, where two signals result in a single output. For example, a logic gate might be an AND gate, where both input wires need to have some electrical charge for the output to be charged. An OR gate, on the other hand, is where one wire or the other needs to be charged, but not both, to give a charged output.

Our neurons are incredibly complicated logic gates. Unlike our electrical analogues, each neuron can perform lots of different gate functions, depending on which signals it receives. Each different triggered function from the input will create a range of different outputs. This is why our brains are so much more powerful and flexible than a computer circuit.

Let us now look at how a signal travels from one neuron to another. From the central neuron mass, a projection called an Axon Hillock extends a long tendril called the Axon. It looks much like a tree trunk, with the branches reaching out to one or more other neurons. The Axon makes it almost all the way to a target Neuron, almost touching a spike from that destination Neuron called a Dendrite. The gap between the Axon and the Dendrite is called the Synaptic Gap, and often just referred to as a Synapse.

Human brain signals are electrical in nature, much like our electronics. Rather than electrons flowing through metal, biology uses ionic flow. Ionic flow is where charged particles move through a fluid to carry the signal. Charged particle signals are much slower than electronic signals, which is why computers outpace us in singular tasks. Due to the complex multiple connectivity of the trunk and branches, and multiple logic operations each Neuron can perform, our neuron networks are far more complex and act in parralel, which means that humans can think faster about complex things than computers can.

The Synaptic Gap is filled with a mostly inert fluid. That is, the fluid itself won’t pass a signal from the Axon to the Dendrite. This is basically the “off” state. The source Neuron receives various signals from other Neurons which results in a calculation in the central Neuron mass. In this example, the result of the calculation charges the Axon Hillock, which triggers an ionic signal to cascade down the dendrite. A way to think about this is somewhat similar to dominos falling and knocking the next domino over, each domino passes on a signal, a change in ion charge. Imagine that the bottom of the domino is on a flexible stand that after being stressed by the tipped domino, stiffens up, straightening the domino ready to receive a new signal.

The elements that make this signal are made of calcium and sodium, and they go back and forth along a membrane through holes called gates, that travels the length of the axon. Calcium Channel Blockers and Sodium Channel Blockers making it harder for this signal to go down the axon in different ways, slowing the signal speed. This is thought to help some kinds of disorder such as epilepsy, some heart conditions and some kinds of anxiety.

When the signal gets to the end of the axon, the end at the synapse becomes charged with electrical potential. When the charge gets high enough it triggers the release of neurotransmitters stored in the axon end in little chambers called vesicles or reservoirs. The neurotransmitter is excreted into the gap, which now passes the charge that has built up at the end to reach the other side, the receptor of that neurotransmitter.

This is effectively the “on” state.

After the Axon end has lost sufficient charge, the fluid in the gap is swept clear, some neurotransmitter is recycled, most is flushed, all reset to pass a signal again. Meanwhile the dendrite is passing the received signal to the Neuron it is part of in a similar way to how the Axon passed its signal.

{Further Reading : Synaptic Transmission [Link]}

Synapse Neurotransmitter Simulator

An experiment to simulate this is to connect one end of a battery to a suitable light globe. Connect the other end of the battery to a wire that goes into a cup. The wire end in the cup should be stripped of insulation. Another wire in the cup, not touching the first wire, goes from the cup to be connected to the other end of the light globe. If it is an LED you are using, check that you have the LED connected in the right direction. Much like an LED, the Axon, Synapses and Dendrite have only 1 direction that they work in. Poor into the cup some distilled water. The LED should be unlit – this is the “off” state.

The cup is the Synaptic Gap with inert fluid in it.

Now add a teaspoon of common table salt to the cup and gently stir it. If the LED has not started to glow, add another teaspoon. Keep adding salt until the LED lights up. You have now added enough of the Neurotransmitter analogue to the Synaptic Gap to pass the signal on. Once you see the light, tip the water in the cup out and put some new distilled water in it to reset the switch.

The Goldilocks Zone

Our bodies work in a complex interconnection of various chemicals. To keep in good condition, our body works hard to keep chemical reserves and usage in an ideal “good zone” and does some on the fly compensation if your levels are just a bit out. For example, if your blood glucose level (blood sugar level, or BSL) is too low, some sugars are released into your blood stream to get it back to “good”. If your BSL is too high, then insulin is released to get your BSL back down to “good”.

Our brain is trying to do the same with our Neurotransmitters. This is mostly regulated by a part of your brain that mostly works on Serotonin. Our brains work the healthiest when our Neurotransmitters are in the right amount of supply – not too much, not too little. That is, in the Goldilocks Zone.

We cover how our Mental Health can vary when we are out of the Goldilocks Zone here.

Neurotransmitters

There are many neurotransmitters used by different types of neurons to send signals across the synaptic gap. We will examine a few of the most important neurotransmitters in mental health.

• Monoamines
  • Dopaminergic System
    • Dopamine
    • Noradrenaline (Norepinephrine USA)
    • Adrenaline (Epinephrine USA)
  • Serotinergic System
    • Serotonin
    • Melatonin
  • Histamine
• Peptides
  • Oxytocin
  • Endorphins
• Amino Acids
  • Glutamate
  • GABA (Gamma-Aminobutyric Acid)

Dopaminergic System

The Dopaminergic System refers to three neurotransmitters, Dopamine, Noradrenaline and Adrenaline.

The Dopaminergic Chain refers to how we create (synthesise) neuronal Dopamine first, unused Dopamine is then converted to Noradrenaline, unused Noradrenaline is then converted to Adrenaline. Unused Adrenaline is then turned into easy to excrete products (eg urine).

If you struggle to make enough Dopamine, you will struggle to make enough Noradrenaline. This is common in ADHD. Another form of ADHD shows another potential problem people can have with the Dopaminergic System, where too much Dopamine is converted to Noradrenaline, undermining your ability to use the Dopamine for things like higher order thinking (executive function).

Dopamine

The neurotransmitter Dopamine is effectively what fuels your frontal lobes, where you do most of your higher order thinking, often simplified to the idea of the Executive Function. Dopamine is also used by the Cerebellum, (hindbrain), for smoothing muscle movements, speech and thoughts; and for the initial processing of sensory input (hearing, vision, smell, touch, taste etc).

If Dopamine is not able to trigger the dendrite side Dopamine Receptors in your frontal lobes well, you have a condition called ADHD. Insufficient Dopamine in your cerebellum can cause conditions like Developmental Coordination Disorder (DCD, old name dyspraxia), Parkinson’s Syndrome, Tics, Monotonism (flat tone, struggle with tone), altered speech patterns (odd pauses), missing many words you mean to say in a sentence, and complexity around sensory (variable sensory, such as feeling hot, then cold, or the light is too bright, now dull etc).

An excess of Dopamine in the frontal lobes can trigger schizophrenic or psychotic episodes. These can also be caused by an excess of Noradrenaline too.

Dopamine is a vital neurotransmitter. It can be thought of as the fuel to enable your Executive Function.

• Empower the Executive Function
  • Concentration
  • Holds short term ideas / data (like mental math rather than writing it down)
  • Problem solving, creative solutions, finding more complex viable answers than the Emergency Centre
  • Big picture task prioritisation
  • Comprehension and connecting ideas, integral to learning concepts

Noradrenaline

• Noradrenaline (aka Norepinephrine for USA) is made from unused Noradrenaline
  
  
  • Situational Assessment via Sensory interpretation and Focus:
    • Hyperfocus vs distractibility vs impulsiveness.
  • Feelings / Mood / Emotions:
    • Freeze / Fawn / Flight / Fight reflex when an emergency is perceived.
  • Determines the priority of tasks.
  • Manage pain perception, ties in with Endorphins (we think).

Adrenaline

• Adrenaline (aka Epinephrine for USA) is made from unused Adrenaline
  • At high levels
    • Suppresses (disengages) the frontal cortex (higher thinking centre aka executive function),
    • Engages primal survival actions (survival mode),
    • Suppresses pain perception
  • At moderate levels, appears to be connected to long term memory storage

Serotonergic System

Serotonin

Serotonin is made from the amino acid component of protein called tryptophan

• Powers the neurotransmitter homeostatic system (prompting direct creation/deletion of neurotransmitters to get to the Goldilocks Zone where able) – this is currently conjecture and we need more studies to confirm this
• First link to decrease alertness/agitation (soporific/sleep, parasympathetic trigger)

Melatonin

• Melatonin is made from unused Serotonin
  • Melatonin can pass through the Blood Brain Barrier
  • High levels, prompts the brain to consider sleeping now if the adrenal level is low
    • Being in darkness / dim light prompts the body to produce Melatonin
  • Low levels, prompts the brain to be awake
    • Bright light / daylight (especially sky blue) prompts the body to delete Melatonin

{Biochemistry, Serotonin}

Endorphins

Oxytocin