Neurons
This is how I would explain the electro-chemical interaction between neurons to a friend.
Imagine standing in a giant room with a large number of other people -- each of you are holding your arms out to either side of your body, like Leonardo Da Vinci's drawing of "Vitruvian Man." The giant room corresponds the brain and the nervous system, and you and the other people are each individual neurons. You have your arms out to either side because neuron cells have a long and skinny central body called the "axon"-so the length of your extended arms corresponds to this part of the neuron -- with receptor areas on either end that have fingerlike filaments, called "dendrites." In reality the field would have to be unebelivably large to actually be equivalent to the brain and nervous, which has billions of neurons. And everybody's fingers would have to be very long, because sometimes dendrites can be exceptionally long.
So imagine that all of the people in the field with their arms out, twiddling their fingers, never actually touching fingers. In other words, the communication occurs without touching, and the communication occurs in one direction: so there's a difference between your left and right hand. In a neuron, the dendrites on one end of the axon contain a cell-body called a "soma" -- let's call this the right hand -- while the other end, your left hand, only contains dendrites, and this...
Communication occurs from the soma, along the axon, towards the axon terminal. In other words, you get information coming in to your right hand, and you pass it along with your left. But you never touch, because neurons communicate between the gaps, or synapses. So it's imagine you are getting chemical information, in the form of neurotransmitters, in your right hand: like somebody nearby is tossing candy into your right hand. When you get enough neurotransmitters to start an electrical process, this is called "action potential": in other words, when your right hand has enough candy in it, this is a signal for the left hand to release signals from its synapses to communicate with the next neuron in the pathway. So the candy you collect in your right hand is a signal to which candy to toss to the next person's hand from your left.
PART 2. Multiple Sclerosis or MS is a disease that affects neurons. In particular the effect it has on the neuron is simple: the central part of the cell, the axon, is wrapped in a protein called myelin.…
