Inside the Brain: Neurons, Myelin, and the Wiring of Thought

WEBVTT
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Welcome to this edition of Psychology Explained by Dr. Curtis Peterson,
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who is trying to bring psychology alive for us all.
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So as I mentioned, really this section is about understanding
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the neural aspects of human
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behavior and mental processes, which really focuses
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on the brain, the nervous system throughout
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the body, and the different neurons and receptors And then
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in the next section, we'll talk about how we get information
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into that system, which is sensations, and then how we,
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um, uh, combined it and
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put it together to have our perception or what we see
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in the world. Okay, so,
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but we're going to start with, uh, the cell and
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its signal, and then we're going to look at different systems of the nervous
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system, starting with what's known as a central nervous system,
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which is your brain and spinal cord, and then
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talk about the peripheral nervous system, which is everything outside
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of the brain and the spinal cord. And then we're gonna look
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at some macrostructures of the brain to see kind of different
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areas of functioning and how
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they work, kind of together in order to create our—
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or to create or associate with our behaviors and mental processes.
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All right. But as I mentioned, we're going to start with the most basic
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structure of the brain, the fundamental part of
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it, which is the nerve cell,
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which it's estimated that we have about 86
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billion fundamental nervous nerve cells. All right,
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and just to kind of give you an idea
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of that capacity, all right,
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we see these large data centers being built.
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They tend to take up a couple acres.
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Many are 2-story high. They consume a
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lot of energy and water.
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And our brain is much that same
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way, other than it would actually take about
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8 of those data centers to equal
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1 brain, right? And you may be thinking,
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well, you know, I'm not ChatGPT, or I'm not an AI that
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can solve these complex problems. But your brain is constantly
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solving complex problems 24 hours
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a day, 7 days a week. And if you want to think about it this
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way, a data center wouldn't be able to constantly
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make sure your heart is beating, your lungs are expanding
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and taking in air, your food is being digested
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when you're sitting, Your muscles on
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your back end actually move so they don't get worn out
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and end up with sores. And if you think about
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the complexity of what the brain has to do,
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let's say you have to be put on life support.
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If you're on life support, you fundamentally have a room
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of about 10 to 12 different machines keeping
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you alive. All right, and our brain is doing
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that 24/7 all the time.
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And then you take the complexity of thought and everything
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else into the equation, and you can see
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kind of how it does actually supersede what,
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what we Even the quickest computer we have.
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Okay. The other thing that we should note is
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like data centers, our brain consumes
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a good proportion of our energy,
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mainly glucose.
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Even though it's about 4 to 6 grams of
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weight, it's, you know, it's— if you do your fist, it's about the
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size of your fist, or if you have small hands, maybe both of them.
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Um, it— but it actually consumes
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20% of your energy input.
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So that little kind of part of your brain actually
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consumes a lot more energy than even your legs do
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when you're running. So, uh,
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if you wonder why we can't make data centers efficient,
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well, we have a brain that tends to be very energy
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inefficient as well. So kind of making that
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kind of analogy.
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Um, I do also want to begin with this idea,
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well, does the size of a brain have to do with,
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um, you know, our, our intelligence and all
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that kind of stuff? And, and, uh, in actuality,
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humans don't have the biggest brain.
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Um, elephants and whales and larger
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mammals than us have larger brains than we do,
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because in nature the brain size is
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in proportion of the size of the species.
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So the larger the species, the larger the brain.
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The smaller the species, the smaller the brain.
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Where humans do diverge from that,
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however, is we don't
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fit that perfect proportion to body size to
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brain size. We actually have oversized
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brains compared to our mammal size.
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So, uh, many have kind
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of theorized that because we do have some empty
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real estate, that maybe that is what
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gave forth consciousness.
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Our ability to do the things that humans can do, be able
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to adapt to almost every environment
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and all of those kinds of things is because we do, compared to
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other species, do have some neural
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real estate that is kind of there without
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any functional purpose, um,
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keeping us alive like it does with other species.
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Okay, so I just wanted to make some of those comparisons
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so you kind of have an understanding where, where we stand
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as far as the capacity of the human brain.
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Okay, the most single,
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um, unit, like I said, is a
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cell. This cell here is kind of a stereotypical
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nerve cell when you think about a nerve cell, and you—
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this is probably the kind of image that comes up.
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I do need to mention that there are different types of nerve
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cells. This isn't the only type or even the one we have the
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most of. There's nerve cells that have very,
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very long axon. If you think of
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your sciatic nerve that runs from your lower
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back to your feet, it is just one long axon.
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That goes from your back to your
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feet. And we have some nerve
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cells, mainly in the brain, that have very, very small,
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small axons. They're almost nonexistent,
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even though they're still kind of there. Okay,
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but going off of this one,
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whoops.
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We can kind of get the basic anatomy of
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the cell. So we start with what are known as
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the dendrites, which are kind of the receiving unit of
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the nerve that is going to receive chemicals
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from another nerve's axon.
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And if enough of that chemical is received
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by these dendrites, Then a message is sent to
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the, what's called the soma or the body of the nerve,
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which then generates what's called an electrical
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chemical reaction down the axon.
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And then if that signal is strong enough, it will release a
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neurotransmitter at its axon
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to the next cell. Okay? And that's the basic
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element of communication. Between these 2.
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Okay, so again, we have a receiving cell,
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we have the body, the kind of executor,
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and then we have where the— where we measure electrical
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pulses in the brain. And then we then
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have the releasing units at the
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end. Okay, now We
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should note that again, we have about 86 to 100
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billion of these. But one thing that
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is different between a neuron and
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the other cells of the body is once that neuron
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is gone, it's gone. This idea of neurogenesis
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and whatnot is really not that
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well supported, actually.
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And the idea of growing new nerve cells comes from stem
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cell research, which— that's actually the stem
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cell that mimics a neuron. It doesn't regenerate
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a neuron. Okay.
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But once these are gone, they're gone.
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And they don't ever die. You have neurons
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in your brain that you had when you
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were, uh, um, uh,
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uh, in your mom's womb.
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Uh, if I think that's kind of crazy to think about
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because the rest of the cells in your body, uh,
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change on about a 4 to 7 year, um,
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um, cycle. So every 4 to
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7 years you have new bones, uh, new vessels,
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new whatnot. Our quickest regenerating
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cells in the body are the ones that are on the tongue and
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the skin, which we actually shed every single day.
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But neurons are just that. So because
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of that, they have to have what are known as supporter
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cells, or what are known as glial cells. And there's 4
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basic kinds of glial cells. Some of them clean
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the nerve. Some of them provide immune defense.
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Others, like the Schwann cells,
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insulate your peripheral nerves to keep them protected.
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They all are kind of like the crew that comes in and kind of
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cleans and protects the neuron and nourishes it.
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Okay. The interesting thing I
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think about glial cells is that they— there
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is an association between
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the number of glial cells you have and
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the amount of cognitive decline you see as you age.
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The more— the more
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you see in decline in glial cells,
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the higher percentage of cognitive
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decline you'll see in older age.
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Okay, which brings up the important point about
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health and nourishment of these different types
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of cells, making sure you're getting the right nourishment. But also,
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we have found that, that notion of lifelong
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learners, those people who stay mentally active
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throughout their lives, have denser and higher
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amounts of glial cells into their older age and
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see less cognitive decline into their older age.
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So that's something to think about, that it's not necessarily the
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nerve cells that are becoming compromised. It's the fact
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that they're— they've kind of lost their immune defense.
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They've lost their waste reduction.
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They've lost their cleaning. They've lost what nourishes
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them. And then that slows them down
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and then slows down the cognitive processes that we see with
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aging. So that,
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those are the nerve cells and the combination. I do
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want to take a minute and talk about myelin.
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Myelin is a little fatty substance that it
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kind of is creates
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kind of these nods around
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the cell. And you can see that there's a little gap— this is called the
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node of Ranvier— where there isn't.
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And myelin has 2 basic
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functions. One, it protects the cell. But 2,
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it rapidly speeds up the transmission of
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a nerve impulse. And that can be illustrated kind
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of using just a basic pen. Let's say we
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have 2— whoops— we have 2
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nerve cells, 2 axons,
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roughly the same size. Use your imagination.
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But one of them has myelin and the other one doesn't.
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Okay, so I'm gonna Use your imagination that
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each of these is a little node of myelin.
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And then I'm going to change the color to blue.
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And what this blue represents is the electrical
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transmission down the cell. So in an unmyelinated
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cell, it looks something If I can write
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right, it looks something like this.
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Okay, note the amount of time. But a
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myelinated cell goes dot, dot, dot, dot,
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done. Okay. Now,
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when we're born, we're born with largely an unmyelinated
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brain. Um, which means that
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the brain of, uh, young ones are quite slower
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than the ones of adults during a short
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period of time during adolescence.
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While during, uh, um,
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trying to think of what it's called.
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During maturation, during, um, um,
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what is it called?
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Anyone know the word I'm trying to think about?
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Oh, during All
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right, when a person goes from being a child to an adult physically,
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uh, I can't remember the term. Oh, this is embarrassing.
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Um, um.
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Anyways, during this period, um,
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a, a person going from childhood to adolescence during a
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very short period of time, their brain goes
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from, uh, being completely unmyelinated—
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not completely, but mostly unmyelinated to
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mostly myelinated. Okay? So if you
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want to make this kind of analogy, it's like
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you ride a bike every single day and then
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the next day you have a Maserati.
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All right? And you— so you can go very much quicker, faster,
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those kinds of things. Puberty is the term I was thinking
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about. When a child goes through puberty,
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this myelin, this rapid myelination occurs.
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Okay, now, why?
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Okay, well, the reason why in
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childhood we have largely an unmyelinated brain is
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largely an unmyelinated brain learns better because
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it's processing the information slower. So it's
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able to make stronger memory and connections
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to other nerve cells.
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Hence, during childhood, the best time to
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learn language is at an early, early age.
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But it becomes more difficult when we get into adulthood.
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When a child in early childhood asks a question
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over and over and over, they're not being— they're
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not trying to be annoying. It's just their brain has to do that
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because it's It's slower and it's trying
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to make those connections stronger.
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Okay. But an unmyelinated brain isn't
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that great when it comes to survival. All right.
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When it, when it needs to respond to
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danger. All right. You can imagine this with
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a maybe a 5-year-old and a fast car is coming towards
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them. They might freeze and try
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to decide what they're supposed to do. But an adult,
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when a fast car is coming towards them, knows to immediately get
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out of the way. Okay, and this is kind of the,
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the reason that when our body
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is maturing, our brain is maturing as well.
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But this is also something that is kind of interesting when we talk
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about adolescence.
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Because again, if you can imagine you're
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riding a bike one day that could go 10 miles per hour the
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one minute and then a car the next day that can go 100
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miles per hour, there's a huge difference in the amount of control
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and everything, okay? So in a lot
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of ways, for many years, the adolescent's brain is processing
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information much faster than they can conceptualize
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and understand it. So for example,
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when you ask an adolescent, why did you do
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that? Maybe they, you know, they did something they weren't supposed
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to. And they answer, I don't
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know. They're probably actually correct.
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They probably do not actually know.
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Because it was their fast, new reacting Maserati
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reacting without them going
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into that decision process on their own.
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Okay, and this brings up an interesting thing dealing
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with parenting. We'll talk a little bit more about this when we get into
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developmental psychology, is we find
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that children, adolescents who have an easier time during adolescence
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and are able to make better decisions have parents
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that instead of saying, well, you're stupid, I'm going to take
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away your gaming this for, for a month
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and you're grounded, versus the
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parent who says, okay, you don't know, so let's start from
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the beginning and we'll go through it together.
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So when you were thinking about this and
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the the parent works through it with the adolescents
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instead of thinking that they knew all along
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why they did something wrong and they're just being defiant.
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Okay, they're probably not being defiant initially.
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They're usually— it's because their brains are going— there
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is processing information much faster
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than their ability to rationalize their
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decisions. And our jobs as parents should be able to— should
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be to close that gap between processing speed
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and decision-making.
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Okay, so that's the importance of myelination.
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And another thing I should note about
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myelination is the form of
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dementia that gets a lot of attention is Alzheimer's.
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Alzheimer's isn't the only type of dementia.
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It is actually— dementia is a larger category,
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and Alzheimer's is a type of dementia. In fact,
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it's not even actually the most frequent type of dementia,
22:47.899 --> 22:50.961
but it is one of the more debilitating types.
22:53.671 --> 22:58.225
One of the things that happens with Alzheimer's is
22:58.401 --> 23:02.362
a kind of a— I should change the color of this so it looks right—
23:03.308 --> 23:07.076
is a black plaque. What it does
23:07.576 --> 23:10.972
is it kind of goes over this myelin sheath.
23:11.181 --> 23:14.917
Okay, and once it's encapsulated this
23:14.933 --> 23:18.060
myelin sheath, it basically suffocates the
23:18.124 --> 23:22.586
axon. Okay, once the axon is suffocated,
23:23.052 --> 23:26.102
it no longer can transmit information to another
23:26.602 --> 23:30.340
cell. And when a cell can't transmit to another
23:30.840 --> 23:34.385
cell, it basically dies. Okay.
23:35.782 --> 23:40.020
And what makes Alzheimer's a cascade is
23:40.052 --> 23:43.279
you really only need this plaque
23:43.408 --> 23:46.777
on a small bundle of cells. Because what
23:47.277 --> 23:50.882
happens is a cascade effect. So that those few bundles of
23:51.382 --> 23:55.338
cells with a plaque on them no longer are transmitting
23:55.515 --> 23:58.705
signals to the cells, to the healthy cells.
23:59.459 --> 24:03.098
But because those healthy cells aren't— are not receiving a
24:03.146 --> 24:06.480
signal, they start to die. And then
24:06.577 --> 24:09.751
it becomes a larger and larger and larger effect.
24:10.296 --> 24:13.759
Okay? So this is another example. We talked about
24:13.887 --> 24:17.358
teenagers and fast brains. And now we talked
24:17.858 --> 24:21.118
about forms of dementia, which starts
24:21.618 --> 24:25.137
with this plaque that grows on the axon and then
24:25.460 --> 24:29.028
suffocates the cell. And then we have a cascading effect.
24:32.892 --> 24:36.621
Okay. The synapse. So our nerve cells actually don't touch each
24:37.121 --> 24:39.914
other, which is kind of interesting when they communicate.
24:40.010 --> 24:43.692
They actually communicate with this little gap
24:45.029 --> 24:49.737
here. And what they communicate with is something you probably hear
24:50.237 --> 24:53.669
of a lot. They communicate with neurotransmitters.
24:54.571 --> 24:58.339
The most famous ones are things like dopamine and serotonin.
25:00.436 --> 25:04.195
And then some of the other ones such as GABA and those
25:04.372 --> 25:08.613
who have different functions, but we'll get to the neurotransmitters
25:09.352 --> 25:14.320
and kind of what they do. But basically neurotransmitters
25:14.512 --> 25:18.701
are released in this, and then if enough is received
25:18.765 --> 25:22.505
by the receiving cell, it will do an
25:22.682 --> 25:26.309
action potential and send an electrical impulse
25:26.809 --> 25:29.406
down the, the, the cell.
25:30.626 --> 25:34.334
Where this kind of is kind of interesting in the area of
25:34.834 --> 25:38.458
psychology, besides what the neurotransmitters are associated with,
25:38.506 --> 25:42.567
which, which we'll get to, is a lot of the theories
25:42.664 --> 25:46.372
on different types of disorders
25:46.872 --> 25:51.236
are based upon this kind of communication.
25:51.509 --> 25:55.731
So for example, the serotonin theory of
25:56.646 --> 26:00.611
depression, which states that the reason why
26:00.755 --> 26:04.945
a person experiences depression is they have a reduced
26:04.993 --> 26:07.497
number of serotonin being released.
26:08.988 --> 26:12.820
And that is based upon the medication
26:12.916 --> 26:15.785
that tends to help individuals with depression,
26:16.298 --> 26:20.274
which are SSRIs, which are serotonin
26:20.547 --> 26:25.035
reuptake inhibitors. Basically what
26:25.340 --> 26:29.732
an antidepressant that works on serotonin does is
26:29.845 --> 26:33.548
these are— these areas here are where
26:33.676 --> 26:36.994
neurotransmitters are recycled. So they're taken back
26:37.042 --> 26:40.958
up into the cell built again, put in vesicles,
26:40.990 --> 26:44.330
and then resubmitted. What an SSRI does
26:44.506 --> 26:49.468
is it blocks the cell's ability to
26:50.768 --> 26:54.542
absorb neurotransmitters back
26:55.042 --> 26:58.251
into it. And so what that does is it makes it
26:58.751 --> 27:02.875
so that more serotonin is available inside
27:02.971 --> 27:06.178
this Uh, between these 2 cells.
27:06.549 --> 27:09.326
Okay. Um, and so,
27:10.068 --> 27:13.006
uh, that's kind of the basis of, you know,
27:13.120 --> 27:15.728
the serotonin theory of depression.
27:16.066 --> 27:20.334
Okay. And we'll see some interesting things
27:20.398 --> 27:24.665
dealing with neurotransmitters when we talk about schizophrenia
27:25.165 --> 27:28.288
at the end of the semester, uh, bipolar.
27:28.996 --> 27:32.406
We'll talk about things like dopamine and serotonin when we
27:32.473 --> 27:35.914
talk about emotions and And motivation.
27:36.511 --> 27:39.789
And so this kind of is an illustration of
27:39.886 --> 27:43.147
how this kind of system, when someone says a neurotransmitter,
27:44.137 --> 27:48.402
you now have this picture in your brain, in your head
27:49.064 --> 27:51.810
of what this is actually looking like.
27:56.022 --> 27:59.487
Okay. And so this is where
27:59.987 --> 28:03.210
we'll, we'll shortly go through these and then we'll call it a day for today.
28:04.113 --> 28:09.219
So we basically have 3 types of neurotransmitters,
28:09.797 --> 28:13.153
ones that are excitatory. So under this is
28:13.185 --> 28:17.649
glutamate and norepinephrine. So norepinephrine
28:17.745 --> 28:20.748
is arousal, vigilance, alertness.
28:22.080 --> 28:25.709
Glutamate is excitatory switch. It's critical for
28:26.209 --> 28:29.932
long-term potentiation, learning, and memory. And then
28:30.029 --> 28:33.177
we have modulatory complexes. So for example,
28:33.258 --> 28:36.246
dopamine is motivation, reward,
28:36.872 --> 28:41.258
motor control. Okay, if you want to think of dopamine,
28:41.531 --> 28:45.194
um, as far as, uh, different things,
28:45.370 --> 28:48.085
uh, substances like cocaine,
28:48.278 --> 28:51.877
methamphetamine are basically a synthetic
28:52.377 --> 28:56.198
type of dopamine. Okay, serotonin is
28:56.696 --> 28:59.843
Uh, mood regulation, um, uh,
29:00.389 --> 29:03.279
and emotions and sleep. Uh,
29:03.295 --> 29:07.117
acetylcholine, uh, does with movement and
29:07.133 --> 29:10.729
memory, much like glutamate. And endorphins
29:10.842 --> 29:13.748
are kind of our neural painkillers. Okay.
29:15.016 --> 29:17.457
And then inhibitory is, uh,
29:18.613 --> 29:21.824
it inhibits parts of it. It pushes the brake.
29:22.130 --> 29:25.704
Okay? The brain's primary brake reduces neural
29:25.752 --> 29:29.887
excitatory things. So an example
29:29.936 --> 29:33.670
of this is a lot of blood pressure pills
29:33.782 --> 29:37.437
are GABA inhibi— are GABA medications,
29:37.629 --> 29:41.092
meaning that it makes it so the brain isn't
29:41.592 --> 29:45.355
sending such a signal to the heart that is creating
29:46.061 --> 29:49.875
the over— the pressure within the blood system.
29:50.036 --> 29:53.838
So it's inhibiting relaxing the heart
29:54.338 --> 29:57.914
and relaxing the blood vessels and everything
29:58.042 --> 30:01.650
so that there's not that pressure in the
30:02.150 --> 30:04.855
system. Okay. All right.
30:05.273 --> 30:08.842
So again, I just wanted to stop and
30:08.907 --> 30:11.041
kind of introduce the cell for today.
30:13.159 --> 30:16.604
And so I'm going to stop the recording. Wow, we made
30:16.637 --> 30:20.205
good time with this, you guys. Thank you for
30:20.705 --> 30:24.379
joining us for this Psychology Explained. I hope you'll join us
30:24.492 --> 30:28.892
in later episodes where we can— we'll continue to investigate
30:29.005 --> 30:31.166
the human mind and psychology.