I’ve never understood on a physical level how the speed of conduction is increased by having myelin create gaps in the flow of the neuron. How does the signal cross the gap, and why does it cross it more quickly than if it were unmyelinated?
Damn, I wish SentientMeat were still around. Since he left, I get no love on my neurology questions.
Think of a linear network of transmitters, where each transmitter has a certain latency in handling a message. It makes no sense to space the transmitters any closer than their maximum range, because you’re adding unnecessary latency. It’s like that with action potentials in neurons. Each un-myelinated patch of membrane transmits an action potential. Myelination effectively removes unneeded ones by electrically insulating them. The signal passes through fewer “transmitters”, less latency is introduced, and the signal transits the same distance in less time.
So it’s like an incredibly short wave radio burst? As I understand it the action potential of the sodium ions depolarizes the next sodium ions in line. If you create a gap between them, then how do they impact each other in the chemical aspect of the electro-chemical transmission?
I am still quite confused.
It’s not the ions that are depolarized, it’s the membrane that is depolarized. The membrane is said to be polarized when there is voltage across it. The voltage is maintained because the axonal membrane contains protein pumps that constantly pump cations (positive ions, specifically Na, Ca, and K) out of the membrane. There are other membrane proteins that serve as passive channels to let the cations flow back in, which causes a voltage drop (depolarization). These gates happen to be triggered by depolarization, so that’s what a nerve impulse is. It’s positive feedback system where action at one gate causes the next gate in turn to be triggered.
It turns out that gates don’t need to be right next to each other to detect the voltage drop, they can be a micrometer or so away, hence the role of the gaps.
Like a radio burst, but actually an electric field. To answer this question directly and simply, an ion channel permits several cations to flow in, which causes a voltage drop. The voltage drop triggers the adjoining ion channel to do likewise, and so on. It takes a brief amount of time to do so, therefore it’s better to space apart the areas that have these gates. Nature solved this problem by covering the intervening space with myelin. voltage-gated ion channels
Great thanks. You’ve answered my question satisfactorily. I’ll revisit it after I’ve gotten a bit more physics under my belt. 