Marker. 1  Noun. A line of credit extended by a casino or cardroom. 2  Noun. A small object placed on top of a player's hand for the purpose of preventing it from being mucked or fouled. 3  Noun. A plastic device used to denote who is in the dealer's position.
Myasthenia gravis is caused by a defect in the transmission of nerve impulses to muscles. It occurs when normal communication between the nerve and muscle is interrupted at the neuromuscular junction -- the place where nerve cells connect with the muscles they control.
Myasthenia gravis, a rare, chronic disorder that causes weakness and rapid muscle fatigue. Muscle weakness that is slowly getting worse requires a visit to a doctor. Sudden muscle weakness and loss of function in one area of the body can indicate a serious problem within the brain (such as a stroke or transient ischemic attack) or spinal cord or with a specific nerve in the body.