Learning Diary, Week 4

Neurotransmitter systems are the complex and interconnected mechanisms that orchestrate chemical signaling in our nervous systems. Chapter 6 of Neuroscience introduced many more terms and abbreviations, here I will outline some of the bigger picture categories and functions gleaned from this week’s reading.

There are 3 major classes of neurotransmitters, these are: amino acids, amines, and peptides.

Of the amino acids, 3 major subtypes are glutamate, GABA, and glycine. Glutamate is the most common excitatory transmitter in the brain, while GABA and glycine are the most common inhibitory transmitters within the brain and spinal chord respectively. Amino acids are present in most chemical signaling functions.

There are 5 key subtypes of monoamines: serotonin, histamine, dopamine, epinephrin, and norepinephrine, the latter 3 of which belong to the category catecholamines. Monoamines are vital for higher level functions like attention, cognition, and emotion.

Peptides are chains of amino acids. One important group of peptides are opioids, which are relevant to the perception of pain.

There are other important neurotransmitters that don’t fit into those 3 major categories, such as acetylcholine, which is released by most neurons in the ANS. Acetylcholine is also used by motor neurons which synapse onto skeletal muscle and trigger movement.

There are 3 rules for what distinguishes a neurotransmitter:
1 – They must be made/stored by/in the presynaptic neuron
2 – They must be released into the presynaptic axon terminal when stimulated
3 – They must create the same effect in the postsynaptic neuron as was triggered by release in the presynaptic neuron

Neurotransmitter systems include the mechanisms for transmitter production, packaging, reuptake, and degradation/recycling. I find flowcharts and lists particularly helpful for memorizing systems with procedural elements, here are those included in neurotransmitter systems:

1. Presynaptic axon terminal
2. Neurotransmitter-synthesizing enzymes
3. Synaptic vesicle transporters
4. Reuptake transporters
5. Degradative enzymes
6. Transmitter-gated ion channels
7. G-protein-coupled receptors
8. G-proteins
9. G-protein-gated ion channels
10. Second messenger cascades
11. Postsynaptic dendrite

The parallel processes going on at any moment in our neurotransmitter systems makes me think of it like an intricately-timed composition. There are so many inputs and outputs – trying to get a handle on the different abbreviations reminded me of learning a new coding language, but our nervous systems have more variables than a computer operating on a binary level.

One of the things that sparked my interest in the book was the mention that calcium is likely important in the formation of memory, via chemical traces. This section didn’t go into much depth, but I am excited to learn more about that in later chapters. This reminded me that I read an article recently about some people are attempting to reinvent computer architecture to mimic brain function through combining transistors and memory capacity on the same circuits (American Institute of Physics, 2020) – I wonder how such neural mimicry would integrate neurotransmitter function?

Citation

American Institute of Physics. (2020, January 15). Reinventing the computer: Brain-inspired computing for a post-Moore’s Law era. ScienceDaily. Retrieved October 4, 2020 from www.sciencedaily.com/releases/2020/01/200115120637.htm

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