Organ music: cells self-organise into organs

Biology involves many different scales. At each scale, one considers what are the essential components and how they interact with one another. 

All living beings are composed of organs which in turn are composed of biological cells. The functionality of an organ emerges from the interaction between cells. 

Part 3 of The Economist's excellent series on biology is How organisms are organised. Here are a few highlights.

The twin processes of differentiation (many different types of cell) and integration (a highly functional structure) [are] at the heart of what makes organs tick.

How are the structures of plants and animals different? Why?

... animals and plants have different relationships with time and space. These different ways of life require different sorts of flexibility. Animals move through space but, once adult, change shape comparatively little over time. Plants stay still in space but change shape a lot as they grow. 
Most animals seek the energy they need by hunting or foraging. Plants’ energy-seeking behaviour is a matter of growing roots to take in water and minerals, and flat, green surfaces to absorb the sunshine and carbon dioxide that make up the preponderance of their food.

Muscles, nerves, and bones need to grow to a pre-arranged design much more than branches, twigs, and leaves do.

A human has about 80 distinct organs. The brain is the most complicated organ. It has about 86 billion nerve cells (neurons). There are 133 types of these in the cortex of the brain. 

Neurons are the essential components. Then one needs to consider how these components interact with one another.

A single neuron may be connected to as many as 10,000 other neurons. There are more than one hundred different types of chemical neurotransmitters with which to send and/or receive messages at the points of connection between.

The figure below shows how neurons are connected to one another via axons. Electric signals travel along the axon by action potentials.

The brain is a highly complex system. There are a large number of components, of many different types, and the large connectivity between them, and a large number of ways they can interact with one another. Given this complexity is it really that surprising that brains can "think" and process complex information. Parenthetically, I think this is another simple reason why I think proposals of quantum consciousness are so fanciful. Before, invoking such speculative ideas I think proponents should first rule out a simpler hypothesis: 

Consciousness (defined in some simple computational sense, putting aside profound philosophical nuance) can emerge from purely classical processes in such a complex system.

Hopfield showed how associative memory could emerge from a model that is much simpler than an actual brain. To me, this gives confidence that it is reasonable to work with the classical hypothesis.

Comments

Post a Comment

Popular posts from this blog

What is Herzberg-Teller coupling?

Image
Is it something to do with breakdown of the Born-Oppenheimer approximation? In molecular spectroscopy you occasionally hear this term thrown around. Google scholar yields more than 3000 hits. But I have found its precise meaning and the relevant physics hard to pin down. Quantum mechanics in chemistry by Schatz and Ratner is an excellent book , but the discussion on page 204 did not help me. "Herzberg-Teller" never appears in Atkins' Molecular quantum mechanics. So here is my limited understanding. Herzberg and Teller wanted to understand why one observed certain vibronic (combined electronic and vibrational) transitions that were not expected, particularly some that were expected to be forbidden on symmetry grounds. " Intensity borrowing " occurred. Herzberg and Teller pointed out that his could be understood if the dipole transition moment for the electronic transition depended on the nuclear co-ordinate associated with the vibration. In the Franck-Condo
Read more

Is it an Unidentified Superconducting Object (USO)?

If you look on the arXiv and in Nature journals there is a continuing stream of people claiming to observe superconductivity in some new material. There is a long history of this and it is worth considering the wise observations of Robert Cava , back in 1997, contained in a tutorial lecture. It would have been useful indeed in the early days of the field [cuprate superconductors] to have set up a "commission" to set some minimum standard of data quality and reproducibility for reporting new superconductors. An almost countless number of "false alarms" have been reported in the past decade, some truly spectacular. Koichi Kitazawa from the University of Tokyo coined these reports "USOs", for Unidentified Superconducting Objects , in a clever cross-cultural double entendre likening them to UFOs (Unidentified Flying Objects, which certainly are their equivalent in many ways) and to "lies" in the Japanese translation of USO.   These have caused g
Read more

What should be the order of authors on a conference poster or talk?

I welcome discussion on this point. I don't think it is as sensitive or as important a topic as the author order on papers. With regard to paper authorship my general rule is that the person who does the bulk of the work, including actually writing the paper should be the first author. Doug Natelson has a good post on co-authorship , that I largely agree with. My only difference is that I am not really convinced that good practice prevails in the majority of circumstances. I fear there are increasing numbers of co-authors, particularly senior ones, with marginal contributions. But, what about conference talks and posters? Many of these are based on work that is already or about to be published. Should the author order be identical as the associated papers? I am not sure it should necessarily be. My tentative view is that the person who writes and submits the abstract and actually prepares and presents the post/talk should be the first author. Perhaps they should also highlig
Read more