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 an autoimmune disorder, in which circulating antibodies cause weakness by blocking acetylcholine receptors at the post-synaptic neuromuscular junction, inhibiting the stimulative effect of the neurotransmitter acetylcholine.yasthenia gravis (MG) is distinguished from congenital myasthenic syndromes (which have similar symptoms) in that MG responds well to immunosuppressive interventions, while congenital myasthenic syndromes do not. Myasthenia gravis more commonly occurs in women under 40 years and men over 60.