LIGHTING UP YOUR WORLD
Meet your Brain!
First part of “Lighting Up Your World” article (about optogenetics for mental health disorders)
Laughter. Joy. Cheers.
That’s right, you are in a stand-up comedy show. The thing is you aren’t feeling any of this; no happy emotion is evoked in such cases for you. On the contrary, you are self-loathing.
You feel different and weird among the rest, so you throw in a few grins and chuckles, but they seem void of any emotion.
The world’s a dark place for you.
Until, someone switches on the light in your brain… literally.
Switching on the light.
If you haven’t caught it already, what I just mentioned was an analogy of how daily life is for someone diagnosed with depression. That’s right — this is normal for 18 million people in the United States alone.
Optogenetics is a field that fuels hope to everyone facing mental illness. It, unlike conventional methods that use electricity, uses light to control cells. It combines the field of optics and genetics to control cell activity, in our case, neurons. Quite literally, that means mind control (woah).
Before we delve deeper into this, we’ll have to meet someone very important (who is the reason I’m able to write this and you’re able to read this)…
Meet the… brain!
(A Recap of High School Biology)
Your brain is the most fascinating organ of your body. Every day, it processes information, helps us understand super-cool science concepts and is the reason you are able to stay without going bonkers. You really do have a lot to thank your brain for, don’t you?
Our brain isn't just a big solid of that wire-like mushy stuff — it contains cells called neurons. Here is what one neuron looks like:
Notice that there are these branch-like structures on the left of the neuron. These are called dendrites.
These dendrites stem from the soma, which is the cell body. It contains everything you’d expect a cell to contain like the nucleus, endoplasmic reticulum etc etc…
The soma leads to the axon, which is that cable-like thing between the nerve ending and the soma. Oh, and you’ll see that it’s exactly like a cable too.
Note: this is the generic structure of a neuron, it can differ in size and shape.
Now, these parts aren’t here just to make you memorize names. They do a lot to communicate messages across our body, which is essentially the reason why you are able to read this!
But how do they do this? How do they communicate these messages?
Answer: Electrical impulses.
So when we say that a ‘message’ is being passed through, we refer to these impulses.
Dendrites have itty-bitty receptors that are designed to pick up signals from other neurons that come in the form of chemicals (neurotransmitters). This causes electrical changes in the neuron. These changes are interpreted by the soma.
What the soma does is take all the information from the dendrites and gathers them in a little space between the soma and axon known as the axon hillock.
If the signal is strong enough, it is sent to the axon.
Our little signal then travels all the way through the neuron and reaches the ending which, to put in science-y terms, is the axon terminal.
This axon terminal will then pass on the neurotransmitter to the dendrites of the next neuron, and this whole thing repeats and repeats until your brain tells you to *thing your thang*.
…And there you go! You now know the basics of the neuron. I’d like to dive a little bit deeper into one aspect of this, more specifically the electrical signalling bit.
Diving deeper (to the molecular level!!)
Our body has a lot of charged particles (ions) floating around and though our body as a whole is electrically neutral, certain parts are more charged than others.
Since unlike charges love to attract to each other, they needed to be separated by a membrane 😢
While this may be sad (why separate true love?), it actually creates energy — potential energy (kind of like voltage ⚡️)
This is known as the membrane potential.
Let’s talk about how this comes to play in a neuron.
A ‘resting’ neuron contains more negative charges compared to the outside of the cell which has more positive charges. This difference is called the neuron’s resting membrane potential. This is usually -70 millivolts.
When our neuron’s membrane potential is negative (like above), it is said to be polarized. (yes it CAN be depolarized)
A neuron isn’t always in a resting state. Its membrane potential changes while it does all the wonderful things it can. Ions flow in and out of the cell through these little gateways known as the sodium-potassium pump.
To make sense of the sodium-potassium pump and why it is called like that, we need to know the specific ions that are in and out the cell.
The outside of the cell has more positive sodium ions whereas the inside of the cell has more also-positive potassium ions (the inside is negative because of the presence of large negatively charged proteins).
Note that these aren’t the only ions present, however, I will only be mentioning them as only they are relevant to this series.
Okay, back to the sodium-potassium pump.
The Sodium Potassium pump is a protein found on the axon of the neuron (and on other cells of the body too!) whose main function is to transport sodium ions out of the cell and potassium ions into the cell.
For every three sodium ions transported out, two potassium ions are transported in.
A conformational (shape) change is obviously needed to do this and this change is powered by ATP (phosphate does all the magic 😌).
This happens so that the membrane potential is maintained and the intracellular (inside the cell) charge of the cell remains negative.
The difference of charges creates an electrochemical gradient. Nature has a little tendency to try and balance out everything, but the only way for this to happen is through the exit of ions.
Our sodium-potassium pumps only do so much to ensure that for every three sodium ions out, two potassium ions are in.
Thankfully, the axon also has ion channels on their surface that allow free movement of ions when their gates are open, which by the way, does so depending on structure and time.
When these gates open, all the ions follow their passion and leave their like (positive) charged friends. Not a very nice behaviour, is it?
This ‘following-of-passion’ is the basis for all events in the neuron.
Let’s see how.
All the action!
Ion channels come in many types, but the one we are concerned about here is voltage-gated channels. These open and close based on the membrane potential.
Important to Note:
- Potassium channels = potassium moves through it
- Sodium channels = sodium moves through it
To make this simpler for the both of us, let’s set a scene here. You are in the couch, dozing off into your afternoon nap. You are too tired to turn off your television and so, you let it play. It’s comfy, your mind is clear and every second, you dive deeper into a dream world. In short, you are in a state of peace.
The next moment, you arouse in shock because of a blaring voice from the TV; someone had switched from your sleep music video to Formula One, unaware of your nap!
Yikes! That certainly was disturbing.
…But what disturbance occurred on your neurons while this happened? How did the electrical impulse get communicated?
What actually happened was that your neuron hit an action potential. (oh yes, you’re right on time for the action!) This happens when the membrane potential goes to -55 mV.
How did the membrane potential end up like that?
Well, a sodium channel opened in response to the stimuli, which meant that the intracellular charge becomes increasingly positive, meaning that the membrane potential was getting higher.
And then it hit -55 mV. And THAT’s when all the action began.
Your voltage-gated channels were now open and all the positive ions rush in, making the overall charge positive 😮
This kicks off communication between neurons and the process repeats in the next neuron.
This is temporary and soon after, repolarization takes place to bring charges back to their optimal state. After a bit of hyperpolarization + action from our sodium-potassium pumps, we are back to -70 mV! Our body really is fascinating, right?
Oh, and don’t forget to thank your neurons for being so quick in doing all of this!
Things can take a turn though, but you’ll have to stick around to see that in the next part of this series!
If you want to jam out on this or just be friends (pretty please), catch me on my socials — Linkedin | Twitter | Instagram | Youtube. Oh, and while you are at it, stay on the loop with my crazy adventures by subscribing to my personal newsletter! Toodles :)
Oh, and here’s a bit about me:
Hey Hey👋, I’m Rania, a 14 y/o innovator in the Knowledge Society. I’m currently researching alternative protein, extended reality and other exponential technologies. I’m always ready to learn, grow and inspire. I’d love to connect; reach out to me on any of my social media and let’s be friends!
