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 is caused by an abnormal immune reaction (antibody-mediated autoimmune response) in which the bodyâs immune defenses (i.e., antibodies) inappropriately attack certain receptors in muscles that receive nerve impulses.