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.
The magic of ion channels in the neurons
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Re: The magic of ion channels in the neurons
#12I 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
Re: The magic of ion channels in the neurons
#13For 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 This contains my absolute favorite figure caption ever: A fresh and lively squid was taken out of the aquarium and immobilized by cutting the nerves conne…
Poor squid. :(
Re: The magic of ion channels in the neurons
#14Interesting. 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:
Re: The magic of ion channels in the neurons
#15Interesting. 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.
It starts with the telegraph equation. Try this magisterial and slightly obsessive book: https://mitpress.mit.edu/books/cellular-biophysics-2-vol-set
Re: The magic of ion channels in the neurons
#16For 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 This contains my absolute favorite figure caption ever: A fresh and lively squid was taken out of the aquarium and immobilized by cutting the nerves conne…
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...
Re: The magic of ion channels in the neurons
#17I 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 memb…
This would explain the 20% (give or take) oxygen requirements of the brain.
Re: The magic of ion channels in the neurons
#18How 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?
Re: The magic of ion channels in the neurons
#19How 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…
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.
Re: The magic of ion channels in the neurons
#20Interesting. 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.
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.