Brains on Brains Week 4: Chemical control of the brain and behaviour

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The blog “A Plastic Journey: Introspection of Brains Learning About Brains” delves into the qualia, feelings and thoughts brought forth in the authors’ brains upon learning about the human brain and its functions. The blog will follow loosely the structure of the course “NBE-E4210 – Structure and operation of the human brain.” The blog is written in the form of a fact-filled, loopy and introspective story. [Logo: Oxford University Press (2018).]

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Chapter 15 was extremely interesting. When the focus is on hypothalamus, autonomic nervous system and diffuse modulatory systems, countless important functions of human life from appetite to motivation and from sex drive to blood pressure start to emerge. This is the area where so many things we would like to be able to control are found, and effort hasn’t been spared either. We often eat too much and crave unhealthy food, and sleepiness gets in the way of night time military operations and studying neuroscience. We also have an ever growing list of substances that are cultivated, prescribed, bought and sold to control the chemicals that control us.

All three systems discussed in chapter 15 have one common basic role: maintaining the brain homeostasis. Homeostasis is the process where brain controls the body’s internal environment like blood pressure, body temperature and glucose concentrations to be compatible with the ever changing external circumstances. Hypothalamus is located below thalamus and along the walls of the third ventricle. Often described as being about the size of an almond, hypothalamus makes up less than 1 percent of the brain mass but its influence on our body physiology is e enormous. Even a small damage to this tiny part of the brain can cause fatal disruptions to our most important bodily functions.

Some especially interesting parts of the chapter included the two details about food and the brain: Enteric division of the ANS and the connection between our diet (like carbohydrates and protein) and the serotonin levels in brain.

Frequently discussed in popularised science articles and podcasts, enteric division is at the same time both fascinating and strange. It consists of two networks with a total of 500 million neurons, which is as much as in the spinal cord. It quite independently (from both symphatetic and parasympathetic nervous systems) controls and monitors things like the transport and digestion of food, chemical status of stomach and hormonal levels in blood, so it’s no surprise it’s sometimes referred to as our “second brain”. Even the neurotransmitters in CNS and enteric system are mostly similar. One of them, serotonin, is linked with our diet in interesting ways.

Like we learned last week when talking about neurotransmitter systems, serotonin, one of the amine neurotransmitters important for many functions from intestinal movements to our mood, is derived from the amino acid tryptophan via a two-step synthesis process. This means the serotonin levels in the brain are limited by the availability of tryptophan in blood, which in turn depends on our diet. The paradoxal process involving other competing amino acids, insulin and blood-brain barrier results in interesting findings, like that reduced daylight during winter makes us crave for carbohydrates and that same serotonin-elevating drugs can help a person with both weight loss and depression.

This underlines the idea that it’s not rational to view a human being as a dualistic combination of “body” and “spirit”. We think and how we eat, and we eat what we are made of. Sleeping too little, feeling happy or cold, being in love, choosing low carb over low fat, it’s all connected.

Posted by Free Willy

The blog "A Plastic Journey: Introspection of Brains Learning About Brains" delves into the qualia, feelings and thoughts brought forth in the authors' brains upon learning about the human brain and its functions. The blog will follow loosely the structure of the course "NBE-E4210 - Structure and operation of the human brain." The blog is written in the form of a fact-filled, loopy and introspective story.
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Brains on Brains Week 3: Neurotransmitters

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The blog “A Plastic Journey: Introspection of Brains Learning About Brains” delves into the qualia, feelings and thoughts brought forth in the authors’ brains upon learning about the human brain and its functions. The blog will follow loosely the structure of the course “NBE-E4210 – Structure and operation of the human brain.” The blog is written in the form of a fact-filled, loopy and introspective story. [Logo: Oxford University Press (2018).]

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Neurotransmitters function as messengers in the transmission of neural signals over chemical synapses. Hundreds of different chemical messengers have been identified. These neurotransmitters are heavily linked to neural diseases. Schizophrenia is heavily linked to high levels of the neurotransmitter dopamine. Parkinson’s disease is characterized by the opposite – low levels of dopamine. Although the origin of these diseases is not a only a deviation from a normal neurotransmitter levels, the existence of a link between neurotransmitters and diseases that alter the personality, memory and self of a person is clear.

Of neurological diseases, schizophrenia is often seen day-to-day lingo as the pinnacle of losing one’s mind. Schizophrenia comes with variety of symptoms. Schizophrenic people can suffer from anxiety and depression, as is often the case with otherwise healthy adults with low dopamine levels. Moreover, schizophrenic people can have a hard time between determining the line between reality and their own thoughts, seeing hallucinations and hearing voices. Although seeing hallucinations in healthy adults is quite rare, hearing voices, when you come to think of it, is quite common. The self of a person is de facto a constant, almost uninterrupted voice narrating our lives, constantly speaking and churning ideas to “us” (whoever that might be).

One of the fundamental ways our brain functions is something we would often label “schizophrenic” even crazy. But where goes the line between a harmless narrator of one’s life and the first symptoms of a mental disease? Currently, there is no clear way of diagnosing schizophrenia (APA, 2013). Are people with a more commanding, demanding narrator like those extremely driven for a certain cause, even if a good one, in fact a few steps further down the path towards insanity? Are the presidents, the super athletes or the top tier scientists of the world in some regard simply tormented by a more demanding narrator of their lives, much akin to the one that often dominates the lives of schizophrenic people commanding them to follow its every whim?

 

SOURCES

American Psychiatric Association (2013). Diagnostic and Statistical Manual of Mental Disorders (5th ed.). Arlington: American Psychiatric Publishing. pp. 101–05. ISBN 978-0-89042-555-8.

 

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The blog "A Plastic Journey: Introspection of Brains Learning About Brains" delves into the qualia, feelings and thoughts brought forth in the authors' brains upon learning about the human brain and its functions. The blog will follow loosely the structure of the course "NBE-E4210 - Structure and operation of the human brain." The blog is written in the form of a fact-filled, loopy and introspective story.
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Brains on Brains Week 2: Synaptic Transmission

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The blog “A Plastic Journey: Introspection of Brains Learning About Brains” delves into the qualia, feelings and thoughts brought forth in the authors’ brains upon learning about the human brain and its functions. The blog will follow loosely the structure of the course “NBE-E4210 – Structure and operation of the human brain.” The blog is written in the form of a fact-filled, loopy and introspective story. [Logo: Oxford University Press (2018).]

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I came to the course as a doctoral student of new media. I study virtual reality, a trendy field where concepts like immersion, perception and embodiment all seem to point towards the need to understand not just human psychology, but the underlying principles that make us (or / and our brains) what we are. Like so many other disciplines, media research has also gained an enormous new insight into human mind through the advancements in neuroscience. While the course book, lectures and everything else seem overwhelming for someone coming from “outside”, professor Ilmoniemi’s introduction lecture’s figure two we already cited in this blog (the brain operates on multiple scales) puts it all in place. Media research operates usually somewhere between language, behaviour and society, so it’s just wise to venture into the molecular and cellular levels too. This week’s theme, synaptic transmission, was a good example of something totally groundbreaking for me.

Probably the easiest and most common knowledge part of the chapter 5 were the neuromuscular junctions. Being more accessible to researchers and having direct effects on bodily functions it’s no wonder many synaptic transmission mechanics were first understood here, before central nervous system. This is also the area most people understand to some extent even without any training in neuroscience. But of course the lecture and the book were mostly focused on synaptic transmissions in CNS.

In addition to the general understanding of the chemical and electrical synapses and the chemistry and physics behind them, some learning highlights for this week included the role of SNARE proteins in binding and fusion of membranes. The delivery of vesicles to presynaptic membrane is key to fast working synaptic transmission. The cooperation of v-SNARES of vesicles and t-SNARES of the outer membrane makes sure that the vesicle “docks” where it should. Although it wasn’t discussed during the lecture, the book’s explanation of botulinum toxins and how they function anchored the mechanism of synaptic transmission very firmly into my memory.

Examples like this are valuable because sometimes it’s easier to remember a certain mechanic by learning conditions where it doesn’t work as intended. To make it short, botulinum toxins are enzymes that destroy certain SNARE proteins, disrupting the transmitter release. Another poison affecting the transmitter release is latrotoxin, which eliminates acetylcholine release in neuromuscular junction. I actually encountered a black widow spider recently while working abroad, and got a colourful description of the symptoms of it’s bite from a lady who was nice enough to take it away from my room. Now I know that nausea, muscle cramps and dizziness are actually swollen axon terminals and missing synaptic vesicles. Another fun animal from the same region, black mamba (dendroaspis polylepis), uses a venom that is a combination of many different toxins. One part of the cocktail, dendrotoxin, interferes with neuromuscular junction transmission through various mechanisms, including by inhibiting potassium channels at pre- and post-synaptic levels, enhancing ACh release from nerve terminals.

Still, for me the most wondrous detail has to be the temporal scale these things happen. We can’t “sense” our own synaptic transmissions in any relevant way, because everything happens in the scale of milliseconds to be useful for us when navigating in human scale world. This reminds me of the discussion about free will: if everything that makes us think and act happens so fast, are we actually the authors of our thoughts or just merely witnessing them rising in our consciousness? I’m sure this is something we can discuss later in the course, but for me chapter 5 gave many new reasons to speculate this.

 

SOURCES

Bear, M.F., Connors, B., Paradiso, M. 2015. Neuroscience: Exploring the Brain. 4th Edition. Lippincott, Williams & Wilkins.

Brylla C., Kramer M. (ed.) 2018. Cognitive Theory and Documentary Film. Palgrave Macmillan, Cham

Grabowski, M (ed.) 2014. Neuroscience and Media: New Understandings and Representations. Routledge.

Harris, S. 2012. Free will. New York, Free Press.

Ranawaka, U. K., Lalloo, D. G., & de Silva, H. J. 2013. Neurotoxicity in Snakebite—The Limits of Our Knowledge. PLoS Neglected Tropical Diseases, 7/(10).  http://doi.org/10.1371/journal.pntd.0002302

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The blog "A Plastic Journey: Introspection of Brains Learning About Brains" delves into the qualia, feelings and thoughts brought forth in the authors' brains upon learning about the human brain and its functions. The blog will follow loosely the structure of the course "NBE-E4210 - Structure and operation of the human brain." The blog is written in the form of a fact-filled, loopy and introspective story.
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Brains on Brains Week 1: Neurons and Glia

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The blog “A Plastic Journey: Introspection of Brains Learning About Brains” delves into the qualia, feelings and thoughts brought forth in the authors’ brains upon learning about the human brain and its functions. The blog will follow loosely the structure of the course “NBE-E4210 – Structure and operation of the human brain.” The blog is written in the form of a fact-filled, loopy and introspective story. [Logo: Oxford University Press (2018).]

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The levels at which a brain can be explained at can be numerous. Possible levels introduced in the course material (NBE-E4210, 2018) include the following, ranging from the very small to the very large, as seen in graph 1 below.

Graph 1: Different levels of systems (Source: NBE-E4210)

Of these levels, Bear et al. (2015) start off by explaining the functioning of neural cells – cells specialized for neural activity. Simplifying the matter to a degree, there are two types of neural cells: neurons and glia. These are broad categories, and there are multiple subcategories within them. Neurons are the information-transmitting and communicating cells that most often spring to mind when thinking about neural cells.

Bear et al. (2015) give a rather tasty analogy: in a chocolate chip cookie, neurons resemble the chocolate chips whereas glia resemble cookie dough that the neurons are attached to. Although von Bartheld et al. (2016) propose a neuron-glia ratio of 1:1 or less (when previously thought to be closer to 10:1), the analogy still bears some relevance to the matter. Neurons form the information transmitting network that is insulated by the glial cells. On the cellular level, these cell types form the landscape of the human brain.

Gaining knowledge about the brain on this level springs to mind a plethora of questions. The human brain constitutes of these two cell types, but what relevance do they bear for the brain, the self, the I itself? What have I gained from learning about these cells? What does it mean to be a neuron? Am I a system, or its parts? Am I an I, am I a brain, am I brain matter? Am I neurons insulated by glial cells? It is undeniable that these cells are what constitute the brain, but the relevance of the cells to the self is unclear. It can be argued that the self is a construct of a higher systemic degree that emerges from a complex system, in this context from the cells. The relation is perhaps best brought to light in situations where the cells are somehow damaged or malignant. This relation is unfortunately clear for people who are born with Pelizaeus-Merzbacher disease, a severe disease which originates from genetic malformations in the myelinating glial cells (Rasband, 2016). People with PMD can suffer from a plethora of motor problems and might never in their whole life learn to walk or speak.

On the cellular level, it is rather clear that the brain consists of neurons and glial cells. It is, however, far from clear what the self consists of on the level of a self. Hedons have been proposed as an unit to quantify the subjective pleasure experienced by an individual. Would it be possible to similarly attempt to quantify buildings blocks of the self of humans or other beings as well? Purely theoretical constructs of this kind might help to discuss and quantify questions around selves and the various degrees of “selfness” that exist in the world.  If measures of this kind were ever to take a foothold in the neurosciences, however, let us just hope that they are called something else than selfies.

 

SOURCES

von Bartheld, C. S., Bahney, J., Herculano‐Houzel, S. 2016. The search for true numbers of neurons and glial cells in the human brain: A review of 150 years of cell counting. Journal of Comparative Neurology. 524:3865–3895.

Bear, M.F., Connors, B., Paradiso, M. 2015. Neuroscience: Exploring the Brain. 4th Edition. Lippincott, Williams & Wilkins.

Rasband, M. N. 2016. Glial Contributions to Neural Function and Disease. Molecular and Cellular Proteomics. 15(2), 355–361.

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The blog "A Plastic Journey: Introspection of Brains Learning About Brains" delves into the qualia, feelings and thoughts brought forth in the authors' brains upon learning about the human brain and its functions. The blog will follow loosely the structure of the course "NBE-E4210 - Structure and operation of the human brain." The blog is written in the form of a fact-filled, loopy and introspective story.
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