Neurons This Is How I Would Explain

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 is called the "axon terminal." However communication between neurons occurs through the gaps between dendrites on the axon terminal: these gaps are called "synapses."

So all these people have their arms out, the length between their arms is the axon, the hands are dendrites, and the right hand contains the soma while the left is the axon terminal with the synapses. 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. This is known as the "myelin sheath." The National Multiple Sclerosis Society (2014) uses the analogy that the nerve is like an electrical cable, where "the axon…is like the copper wire...and the myelin sheath is like the insulation around the wire."

Multiple sclerosis involves damage to the myelin sheath of the axon for reasons that are not fully understood: scientists believe that either the myelin is attacked by the body's own immune system (as an auto-immune disorder) or else the cells that produce the protein begin to fail. Either way, the damage to the axon's myelin sheath damages the ability of a neuron to pass the electrical signal along the axon, and the progressive damage affects the ability of the nervous system to communicate. Because this is an attack on the neurons themselves, MS can take a broad range of symptoms, but the most familiar is probably the progressive damage of the motor neuron system, affecting a person's movement.

There is no known cure for MS, but there are various different subtypes of the disease, which differ in how quickly they act. However, if I were diagnosed with MS, my life would change drastically. I would certainly realize that the ability to walk and move is dependent upon a functional nervous system, and not the sort of thing anybody should take for granted.