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.
Received 13 August 2008, Accepted 20 January 2009, Available online 22 April 2009. Myasthenia gravis is a disease in which antibodies directed at nicotinic acetylcholine receptors are produced, leading to a deficiency of acetylcholine receptors at the neuromuscular junction.This results in impairment of muscular excitation, which appears clinically as fatigable muscle weakness.yasthenia gravis affecting one or a combination of the extraocular muscles without ptosis is less common; however, cases such as bilateral internuclear ophthalmoplegia without ptosis have been described in the literature.