June is Myasthenia Gravis Awareness Month!

In normal health, the nerve releases acetycholine (AcH), a chemical that goes from nerve to muscle receptors (green area) and makes the muscles work.  Lots of balls (the ACh) are created, sent, and then broken down into components, ready for the next flush to move muscle.  

In Myasthenia Gravis, my immune system has made some antibodies that have attached themselves to the receptors blocking them so the ACh can't come in and trigger the muscle to move.  
There are literally millions of these receptors all over the body on the voluntary muscles.  Having them blocked makes me weak.  

Myasthenia -- blocked receptors
by antibodies from immune
system of the Rambler so muscle
contractions are weak

Prednisone is used to force the immune system to shut down (I am about at 50% or less right now on output after a week), and thus keep them out of the receptors (the green Ys).  Another medicine I take keeps the little balls (the ACh) from breaking down so quickly so they are reusable for a while.  (this is my understanding of what is going on, although maybe my myasthenia has weakened that too!).   
I found these images at a good basic website on myasthenia located at Myasthenia link