reasons for fatigue by lee – rebuild

i will try & attach lee’s figures. if not shown you can ask me for a copy & i’ll e it to you. oops, can’t even try – the figures are 10X too big.

The Reason for Fatigue
Dear Friends:

This thread is in response to questions about the cause of fatigue with GBS. The information from these posts were taken from a lecture given by Dr. Joe Phelps at our local GBS Support Group and research I did in my old College Anatomy books. I tried to simplify this enough so that you don’t need a background in molecular biology to understand it. If you want a deeper explanation, I will try to provide it, but it has been 20 plus years since my last chemistry class.

In Figure 1, you can see the electrical configuration of a resting nerve axon. You can see that there are negative charges on the inside of the nerve and positive charges on the outside of the axon. There is about a 70 microvolt difference between the negative and positive charges.

In Figure 2, you can see a nerve impulse causes a switching between the negative and positive charges across the membrane of the nerve axon. This switching ripples down the nerve as seen in the middle drawing and the drawing to the right. This rippling is actually pretty slow. It travels about a half meter per second. Each ripple requires a small amount of energy which it recieves by the chemical breakdown of nearby protein molecules.

Attachment: figure1-2.jpg This has been downloaded 21 time(s).

In Figure 3, you can see how the myelin sheath speeds up a nerve signal. The nerve signal will jump from point ‘A’ to point ‘B’. It will have a ripple or two in the gap between the myelin sheaths and then jump from point ‘C’ to point ‘D’. The speed of a nerve signal through healthy myelinated nerves is about 70 meters per second, or roughly 140 times faster than rippling through a nerve without myelin. It is also much more energy efficient. The same amount of energy required to power one ripple is exactly the energy required to produce one jump across a myelin sheath. The energy efficiency of myelin is between several hundred and a couple thousand times that of a nerve without myelin.

Figure 4 shows a nerve which was damaged as a result of GBS. Most nerves in the body have at least some amount of damage after GBS. The nerve impulse will still jump where there is a functioning myelin sheath, but it is reduced to rippling in the gaps. This rippling in the gaps is the cause of fatigue.

Attachment: figure3-4.jpg This has been downloaded 21 time(s).

When a nerve begins to heal, some damaged myelin cells recover enough to function, and cells that die are not replaced. Neighboring cells stretch out lengthwise to fill in the gaps. Myelin cells can only be stretched so far, so some gaps will remain, as you can see in Figure 5. Another cause of energy inefficiency is that a jump across a myelin sheath can only go so far. If the myelin cell is stretched too far, the jump will not end at the end of the myelin cell, as seen at the left side of the figure, and the nerve impulse will be forced to ripple, whether there is a myelin sheath or not.

Attachment: figure5.jpg