Posted in Psychology & Medicine

Viscera: Brain

(Learn more about the organs of the human bodies in other posts in the Viscera series here: https://jineralknowledge.com/tag/viscera/?order=asc)

(NB: I have written MANY ARK posts about the brain and all the delightful ways it screws up. Some of them are probably the most interesting posts on my blog. Please click the hyperlinks to check out the various related articles! 😀 Alternatively, here’s a convenient list: https://jineralknowledge.com/tag/brain/?order=asc)

Among the many organs of the human body, no organ comes close to the magnificent complexity that is the brain. The brain acts as the command centre of the body. It receives massive amounts of information through the various senses, processes it and sends out electrical signals to control how the body operates. Not only does it control “basic” functions such as movement of muscles, controlling organ functions and regulating homeostasis, it is also responsible for the so-called “higher functions” such as consciousness, emotions and cognition. It is the true seat of the mind and soul.

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The brain is the only major visceral organ not located in the trunk (body). It is enclosed in the cranium of the skull, which acts as a protective casing. Because it is a closed box, even a small increase in volume (such as due to a bleed or a tumour) can cause extreme pressures to build, causing severe problems. The entire brain and spinal cord are bathed in a fluid called cerebrospinal fluid (CSF), all enclosed by a sheath made of three layers (dura, arachnoid and pia maters). The brain sends out nerves to the rest of the body, which act as electrical wiring transmitting signals. These include the cranial nerves and the spinal cord, which leaves the bottom of the skull down the spine. The spinal cord branches off into many nerves that supply every nook and cranny of the body. The brain itself is made up of two large hemispheres, which are connected by a bridge called the corpus callosum. Despite popular belief, the actions of the two hemispheres are much more complicated than “analytical vs. creative”. The brain also encompasses the cerebellum (the small stripey structure at the back), which controls coordination and speech articulation, and the brainstem, which is involved in autonomic control of life-sustaining functions such as breathing, and also the source of the cranial nerves.

In the last century, scientists have learned that specific parts of the brain play a specific role. This thought started with the field of phrenology, where small areas of the brain were mapped to a certain mental faculty, such as love, wit or destructiveness. Although this turned out to be complete hokum, the idea stayed and we now know the actual functions of each part of the brain. The brain is broadly divided into four lobes: frontal, parietal, temporal and occipital. The frontal lobe is the domain of thought, personality, motor function and other higher functions. The parietal lobe is related to spatial awareness and sensory functions (such as touch). The temporal lobe is linked to hearing, comprehension of language and storing new memories. The occipital lobe is primarily associated with vision. The brain can then be subdivided into more focussed areas, such as Broca’s area that governs speech and Wernicke’s area that governs listening. It should be noted that the four lobes only describe areas on the surface of the brain (cerebral cortex) where the higher functions belong. The inside of the brain is just as complicated and has many different parts, such as the hypothalamus that is involved in homeostasis, and the hippocampus that converts short-term memories into long-term memories.

How does a lump of cells weighing around 1.5kg produce such wondrous abilities such as philosophical thought, deduction, emotions and calculation? The truth is that we still do not know how the brain functions exactly. However, we know that the brain is composed of a large number of neurons (nerve cells) – about 100 billion of them. These neurons connect to one another via a synapse, which is a gap between two nerve cells where neurotransmitters travel to and fro (allowing electrical impulses to jump from one neuron to another). Using these connections, neurons form an unbelievably intricate and complex network of electrical activity. Because one neuron can connect to many more others, the number of synapses is estimated to be around 100~1000 trillion – significantly more powerful compared to any computer in the world. The number of synapses directly correlates to intelligence and it seems intellectual activities such as reading a book increases the number of synapses in the brain. We have yet to understand exactly how the brain uses this incredible computational power to produce cognition and self-awareness.

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(Video of neuronal activities in a zebrafish brain)

Because the brain uses electrical impulses for most of its functions, a common abnormality that is seen with the brain is when the electrical activity becomes disorganised and out of control – a seizure. This abnormal electrical activity may be due to a focal problem such as a tumour, or a generalised misfiring of neurons or altered regulation of electrical activity. When a seizure happens, the disorganised activity results in the brain not being able to function normally. For example, the most common consequence is a fit (tonic-clonic seizure) where every muscle spasms out of control, because the muscles are overloaded with chaotic signals. Focal seizures can cause fascinating symptoms depending on the location, such as temporal lobe seizures causing religious visions (hallucination). This also disrupts consciousness, which is why most epilepsy patients do not remember the event.

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Posted in Psychology & Medicine

Phineas Gage

On September 13, 1848, a 25-year-old foreman named Phineas P. Gage was working on a railroad with his work team. In an unfortunate turn of events, as he was using a tamping iron (large iron rod with a pointed end, measuring 3 feet 7 inches in length and 1.25 inches in diameter) to pack gunpowder into a hole, the powder detonated. The forceful explosion drove the metal pole skyward through Gage’s left cheek, ripped into his brain and exited through his skull, landing dozens of metres away. His workmates rushed to Gage’s assistance (who they presumed to be dead at the time of the accident), and to their surprise, found that he was still alive.

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In fact, Phineas Gage spoke within a few minutes of the incident, walked without assistance and returned to his lodging in town without much difficulty – albeit with two gaping holes in his head, oozing blood and brain everywhere. He was immediately seen by a physician who remarked at his survival. In fact, it is reported that he was well enough to say: “Here is business enough for you” to the doctor. Another physician named Dr John Harlow took over the case, tended to the wound, fixed up the hole and recorded that he had no immediate neurological, cognitive or life-threatening symptoms.

By November, he was stable and strong enough to return to his home, along with the rod that nearly killed him. His family and friends welcomed him back and did not notice anything other than the scar left by the rod and the fact that his left eye was closed. But this was when things started to get interesting.

Over the following few months, Gage’s friends found him “no longer Gage”, stating that he was behaving very differently to the man who he was before the accident. Dr Harlow wrote that the balance between his “intellectual faculties and animal propensities” had seemingly been destroyed. Gage became more aggressive, inattentive, unable to keep a job, verbally abusive and sexually disinhibited. He would frequently swear using the most offensive profanities and would be as sexually suggestive as a March hare. How did the iron rod cause such a dramatic change in Gage’s personality?

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Phineas Gage would go on to be one of the most famous patient case histories in the history of modern medicine. His case was the first to suggest some sort of link between the brain and personalities. Neurologists noted that the trauma and subsequent infection destroyed much of Gage’s left frontal lobe – the part of the brain that we now attribute to a person’s logical thinking, personality and executive functions. It is in essence the “seat of the mind”. Ergo, Gage’s loss of one of his frontal lobes meant that his control of bodily functions, movement and other important brain functions like memory were undisturbed, while his “higher thinking” was essentially destroyed (he was essentially lobotomised). This explains Dr Harlow’s observation of his “animal propensities”.

Thanks to this case, a great discussion was sparked and the idea that different parts of the brain govern different aspects of the mind was conceived. We are now able to localise almost exactly where the language area is, what part controls movement and how a certain piece of the brain converts short-term memory into long-term memory.

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