The magic of ion channels in the neurons
i-kh.netFor the Nobel winning work on this from long ago, I heartily recommend:
Hodgkin, A. L. (1958). The Croonian Lecture: Ionic Movements and Electrical Activity in Giant Nerve Fibres. Biological Sciences, 148(930), 1–37. Retrieved from http://www.jstor.org/stable/83088
A fresh and lively squid was taken out of the aquarium and immobilized by cutting the nerves connecting the head with the stellate ganglion. The mantle was opened ventrally by a single cut and was spread out under cooled oxygenated sea water in a transparent dish. Using a motor car headlamp to illuminate the animal and a binocular microscope to watch the penetration,...
Somewhere in the multiverse, a scientifically curious Heptapod takes a fresh and lively humanoid from its terrarium and immobilizes it by cutting the nerves connecting the stellate ganglion...
Ender's Game series comes to mind.
Poor squid. :(
Wir müssen wissen – wir werden wissen. - Epitaph of David Hilbert
We do what we want, because we can. - GLaDOS
Take your pick of rationales, it's not gonna end well for Mr. Squid.
Interestingly, the experiment in Figure 2 was to demonstrate that action potentials could be generated from isolated neurons in buffer solution just as well as they could from an exposed neuron in situ -- so the squid still dies, but it's not tortured to death.
I sometimes wonder if the phrase "they are an egg head" is not so much to do with baldness but more to do with knowledge and intelligence. Phosphatidylcholine (aka Lecithin found in Egg Yolk and elsewhere - 4 egg yolks a day to meet RDA levels) can do wonders for your cell membranes and Vitamin B5 (pantothenic acid) does wonders for your myelin sheaths. I'd be surprised if F1 drivers & fighter pilots werent supplementing above RDA levels with these. Using Potassium Chloride (sometimes called the good salt) helps one to relax in the evening, and sodium chloride as a pick me up in the morning. I wonder if this neuronal ion exchange is anything like the Sodium - Potassium ATPase pump found in other cells as they seem similar. Life is just a complex real-time chemical reaction.
How might the nervous system have evolved?
Wikipedia says: "Action potentials, which are necessary for neural activity, evolved in single-celled eukaryotes. These use calcium rather than sodium action potentials, but the mechanism was probably adapted into neural electrical signalling in multicellular animals. In some colonial eukaryotes such as Obelia electrical signals do propagate not only through neural nets, but also through epithelial cells in the shared digestive system of the colony."
So, the first "thought" was "hungry, want food"?
And everything we do to get to the 7/11 for snacks is built on that?
cells can coordinate by diffusion of signal molecules larger multicellular organisms can use circulatory transport to reduce latency of signals. larger complex organisms coordinate systemic functions with neurons and the electrical signaling between distant parts of the body.
latency is not a good thing to have when you are a motile animal, it limits your overall size and complexity. animal phyla with nervous systems were able to evolve larger bodies avoid being consumed by being too big to eat and became consumers of smaller organisms.
I read somewhere that a significant fraction of the energy budget of the human body is spent on ion pumps (the difference is that ion channels are passive and ion pumps uses energy in form of ATP). That's because keeping an electric potential[1] across the cell membrane drives the mechanism described in this post (and others, like muscle contraction)
Anyway an overview of ion transport mechanisms across the cell membrane is [2]
[1] https://en.wikipedia.org/wiki/Electrochemical_gradient
[2] https://en.wikipedia.org/wiki/Membrane_transport_protein
This would explain the 20% (give or take) oxygen requirements of the brain.
Interesting. I knew most of that more or less but didn't know the mechanism by which the myelin sheath speed up the propagation of action potentials but it makes sense.
Hodgkin and Huxley, who figured out how the basic mechanism underlying action potentials, worked on the squid giant axon because it's so large, up to 1.5mm in diameter. And the reason is large is that invertebrates do not have myelin, and the large diameter helps speed up signals:
It starts with the telegraph equation. Try this magisterial and slightly obsessive book: https://mitpress.mit.edu/books/cellular-biophysics-2-vol-set
Interesting. Oliver Heaviside continues his posthumous exploits.
I’m currently studying ion channels from a biophysical perspective for my PhD. Beyond their fascinating role in neuronal physiology, check out the incredible chemistry and biophysics! A great introduction is MacKinnon’s Nobel lecture: https://www.nobelprize.org/uploads/2018/06/mackinnon-lecture...
Hate to be the guy to ask this but I like to dig into conspiracy shit like: “5G is bad for our health”.
One of the theories is 4G & 5G cause mess with the electrochemical gradient and voltage gated ion channels. Given you are studying them, whats your opinions on this even being possible?
Remove the shadow from the website's title.
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Thanks! we've changed to that from https://i-kh.net/2020/08/26/how-signals-propagate-through-ne....