We had a splendid lecture last year about brain function from a Cambridge University neuroscientist. In it he highlighted a few commonly misunderstood ideas about how the brain works. It was very interesting and that is why I took note when the following video appeared in my YouTube in tray. ASAP Science, a YouTube channel, has been repeatedly recommended to me by Ronnie and I am glad I finally got around to browsing its contents.
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There are some more brain related articles on the blog such as this one, this one or this one. Neuroscience is a very exciting area of research at the moment as fMRI scanners and other recent inventions are allowing us to watch the active areas of the brain under different conditions. An fMRI (functional magnetic resonance imaging) scanner monitors the changes in blood flow to different parts of the brain as those regions increase or decrease in activity. Wikipedia puts it rather nicely…
When neurons become active, local blood flow to those brain regions increases, and oxygen-rich (oxygenated) blood displaces oxygen-depleted (deoxygenated) blood around 2 seconds later. This rises to a peak over 4–6 seconds, before falling back to the original level (and typically undershooting slightly). Oxygen is carried by the haemoglobin molecule in red blood cells. Deoxygenated haemoglobin (dHb) is more magnetic (paramagnetic) than oxygenated haemoglobin (Hb), which is virtually resistant to magnetism (diamagnetic). This difference leads to an improved MR signal since the diamagnetic blood interferes with the magnetic MR signal less. This improvement can be mapped to show which neurons are active at a time.
Neurons are nerve cells (you can read more about them here) and there are thought to be about 86 billion neurons in the human brain. This contrasts favourably with other species although I have struggled to find consistent numbers on the Internet – baboon (14 billion), gorilla (43 billion). The largest brain in the Animal Kingdom belongs to the sperm whale but it is the relative number of neurons devoted to the different parts of the brain that give each species its particular abilities. Crows, for example, have very small brains but they are capable of quite complex problem solving because their brain is structured to make this possible. The human brain consumes about 25% of our total energy intake, which is very high in comparison with other species. I have seen it suggested that the development of cooking allowed us to release more nutrients from our food and hence the capacity to devote more of it to supporting our brains. This made the evolution of larger, more complex brains a possibility. Without this step our bodies might not have been able to spare the resources to support such well-developed brains.
Questions…
- What name is given to nerve cells that carry signals to muscles?
- Which chamber of your heart pumps blood to the brain?
- Which artery is unusual in that it carries deoxygenated blood?
- Name the four major taxonomic groups other than the Animal Kingdom.
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