For those of you who know me know that I am, simply put, neuro-obsessed. Here’s where I try to justify that.
Think about the human body and how incredibly complex it is. Think of all the chemicals that course through your bloodstream to regulate this organ or that, that allow you to grow and mature. Think of the electrical and structural precision that is needed to keep your heartbeat normal. Think of the myriad events that go on to maintain normal digestion even when you are unaware that it is going on.
Now think of the brain and think of the fact that it regulates all of it. A three-pound (give or take a few ounces), gelatinous and convoluted mass of neural tissue sitting comfortably in your cranium regulates all of it. I think that’s pretty cool, right?
Consider this a kind of (grossly simplified) neuroscience primer from someone who has neither an M.D. nor Ph.D (so take it for what it’s worth).
So most people know that the nervous system is composed of the brain, the spinal cord, and the nerves that come out of the spinal cord. The brain is a structure though, quite strange to look at (and even stranger to feel) it is the work of extreme developmental precision. Even the slightest upset in development (in utero) can alter brain function drastically, where the earlier it occurs during pregnancy, the more pronounced the adverse outcome.
The brain does have distinct areas that are devoted to a set of functions, but one cannot say absolutely that one area is exclusively for one function. Example: there is no one area devoted exclusively to memory. There are a handful of locations that contribute to it (hippocampus, medial temporal lobe, amygdala, etc.). The brain (as well as most of the nervous system) is very plastic, that is to say, it is always changing and adapting to fit its environment. This is especially true in the case of injury. Neural tissue in adjacent parts will take over the function of an area that is either itself lost to injury, or loses function because the part it controls is no longer there (as in the case of an amputated limb). This probably explains, in part, the phenomenon of phantom limb pain.
Oddly enough, the majority of the nervous system is glial tissue. Glia (or glial cells) are accessory cells that ensure proper neuronal function. So most nervous tissue are so-called helpers for the neurons. I suppose it makes sense, neurons are prized commodities, and need to be kept in proper condition.
Nervous system function, for most people, is something that is very anthropomorphized. Neurons “talk” to each other, the brain “tells” organs what to do, etc. etc. That’s not a bad way of looking at it, they are after all, communicating. I think it took many years for me to realize just how molecular the whole process actually is.
Taking a step back before diving into chemicals, this is probably what we all learned in high school about the neuron and its structure.
Dendrites are where the neuron receives inputs from other neurons, the axon is where the action potential is conducted, and the signal is sent out to other dendrites on other neurons from axon terminals across synapses (small spaces between the terminal of one neuron and the dendrite of another). Yet not all neurons look like that, and not all neurons synapse on other dendrites. Some have large, dendritic arbors (heh dendrite comes from the Greek for “tree” and arbor means the same thing), some are pyramid-shaped, some even have multiple axons. Some, like motor neurons, have axons that extend for meters to reach from the head to the lower spine, or from the spine to the foot. It all depends on the function of the neurons, and its location in the nervous system. I’m not sure there’s another part of the body with such diversity in one cell type. Feel free to correct me if I’m wrong.
Neural function (as with most other organs) is heavily based on chemical compounds (i.e. neurotransmitters) and ions (charged atoms). X may encourage the neuron to fire–thus sending the signal along its way–while Y may inhibit the neuron’s ability to fire (as illustrated in the grossly oversimplified diagram below where glutamate is X and GABA is Y). Each molecule has its own receptor and/or ion channel to encourage certain ions to come into the cell or leave–which alters the electrical properties of the cell to encourage or discourage firing–or to even alter the gene expression on that cell to change the way it reacts.
We literally think and function in terms of neurotransmitter and ion concentration.
Even a shift in something relatively tiny (as far as size goes) like potassium ion concentration can cause either muscle cramping (which is often seen with hypokalemia or low blood potassium ion concentration) or muscle weakness (which is often seen with hyperkalemia or high blood potassium ion concentration). The alcohol you drink acts on the same GABA (an inhibitory neurotransmitter) receptor (though different region) that the benzodiazepines or barbiturates you take act on, and they cause the same effect: a relative inhibition of a range of functions by letting more chloride ions into the neurons being affected. Shifts in dopamine, norepinephrine, or serotonin (or some combination of the three) are linked to (sometimes dramatic) changes in mood or other things. Drug dependency is largely dependent on how a drug can alter the very structure of neurons so that in the absence of the drug, the brain behaves abnormally.
I think I got drawn to neuroscience not so much because of how interesting it is to know how the brain and nervous system function when things are going normally (though that is pretty cool). I think it was because I found it cooler to see how things in the brain and the nervous system can go terribly wrong, and its cause maybe something as minute as clipping off the end of one molecule (as is seen with botulinum toxin and its cleavage of SNAP-25, a molecule very important to releasing neurotransmitters from vesicles in neurons into the synapse) or something as large as a hematoma (bleeding in the brain or surrounding layers, called the meninges). Even conditions like obsessive-compulsive disorder and schizophrenia have neurological correlates, though we don’t know to what extent. Neuroscience and neurology needs to, therefore, be both nuanced and broad in its approach to solving problems associated with altered neural function, considering both the molecules at play and the gross anatomy. Just the nature of the brain and its role in the body forces one to take into consideration, the whole picture i.e. all organ systems and their function.
It’s great to see neuroscience education being encouraged by the likes of the Society for Neuroscience and the Dana Alliance. There is a Brain Awareness Week held every year across the world. This year’s Brain Awareness Week is going on from March 16th through the 22nd, culminating in the National Brain Bee. The National Brain Bee is a high school, neuroscience Q&A competition that tests everything from neuroanatomy (sometimes on real brains!), development, the senses, and neurological disorders, among other topics. The winner of the National Brain Bee will face off against competitors from other countries in the International Brain Bee. All in all, it’s a very cool experience, and is a great way to introduce neuroscience to students, and maybe even spark their own interest in the subject. Here’s to hoping this year’s competitors enjoy their experience, and perhaps even make the decision to pursue further study in neuroscience.
The brain is really the final frontier in the human body, so only further research and support for these research projects can succeed in helping us understand that which makes us human.
P.S. To those (friends or other readers) in neurology, neuroscience research, or other neuro fields, if you see anything wrong with the post, please comment and clarify. Thanks!