The neuronal worm

The neuronal worm. The human brain is frequently hailed as the most complex structure that we know of, and rightfully so. It is responsible for everything that we do, all the things that we associate with the human condition. Love, hate and everything in between seems to arise from the activity of the roughly 100 billion nerve cells (neurons) within our heads.

Before I go on, let’s think about the following: what does it mean to have 100 billion of anything? Frequently, we speak of billions (and even trillions in these difficult economic times) without quite understanding what these numbers really mean.

Suppose that you are asked to give a presentation in which you must show pictures of each of the neurons in a typical human brain. For example:

Now, if you want to show 1 slide per second, each slide showing 1000 neurons, how many seconds would you need to show all 100 billion neurons in a human brain?

Let’s see:

100,000,000,000 / 1000 neurons per second = 100,000,000

(100 million seconds)!

In other words:

100,000,000 seconds x (1 minute/60 seconds) x (1 hour/60 minutes) x (1 day/24 hours) x (1 year/365 days) = about 3 years and two months!

Also, let’s not forget that neurons must communicate with other nerve cells; this is the name of the game in brain function! A typical neuron has about 30,000 connections with other neurons; these are called synapses.

Finally, our brain is not just neurons. It also contains another type of cell, different than neurons, called glial cells. They are thought to be about ten times more abundant than neurons and have been found to affect neuronal function.

Complex enough for you?

Ok, how can we hope then to understand how something as complex as the human brain functions? Well, one approach that scientists use is to study a small fragment of the whole. For example, how would you describe this?

You have several options. You may choose to list all the colors, or say something like “many rectangles of different colors”. In any case, in order to describe this figure you will need to invest more time and effort than to describe this:

The idea is that if we are able to describe in some detain a small part (say, one neuron), we hope to be able to extrapolate and apply this information to a much bigger system (say, a brain). In other words, a simpler system is easier to study than a more complex one. This is the so-called reductionistic approach, which has proven very useful to understand this nature of ours. It is far from perfect and sometimes it is very difficult to apply, but we have to start somewhere right?

Life scientists use many simpler biological systems to study general aspects of biology. This is possible because all life on earth is related. Animal models have proven one and again to be very useful to understand aspects of human physiology. Recently, an invertebrate animal model, the planarian worm, has been rediscovered as a very interesting model in neurobiology research. We will begin to explore the study of this “neuronal worm” and its possible applications to brain research in my next blog. Thank you!

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