Neuromuscular transmission failure

Myasthenia gravis is an autoimmune disease resulting from production of autoantibodies against AChR at the motor end plate, causing defects in neuromuscular transmission. Depending on the muscles affected a patient may develop dysphagia or respiratory failure [1]. The appearance of pathological forms of erythrocytes such as stomatocytes, echinocytes etc., in peripheral blood causes microcirculation disorders [2]. 

Paralysis can take place anytime there is a failure or interference in the transfer of biochemical impulses from nerve to muscle. On the other hand, hyperactivity of neuromuscular transmission can lead to minor twitches and cramps or to severe spasms as in tetanus (lockjaw) or amyotrophic lateral sclerosis (Lou Gehrig disease). There is still much to learn about both hyperactive and paralytic cases, but new research on DNA and immunology is proving helpful. 

Fatigue (defined as a decline in force following repeated contractions) can occur as a result of a failure to activate motoneurons (commonly referred to as central fatigue) or from failiire in neuromuscular transmission, excitation-contraction coupling, or from the mismatching of energy... 

Fig. 6.6 Characteristics of neuromuscular response following repeated nerve stimulation. Depolarisation block, with no fade, is characteristic of failure of neuromuscular transmission in the cholinergic syndrome produced by antichohnesterase compounds such as sarin...

In-Vivo Percutaneous Implant Experiment. The principle of percutaneous attachment has extensive application in many biomedical areas, including the attachment of dental and orthopedic prostheses directly to skeletal structures, external attachment for cardiac pacer leads, neuromuscular electrodes, energy transmission to artificial heart and for hemodialysis. Several attempts to solve the problem of fixation and stabilization of percutaneous implants(19) have been made. Failures were also attributed to the inability of the soft tissue interface to form an anatomic seal and a barrier to bacteria. In the current studies, the effect of pore size on soft tissue ingrowth and attachment to porous polyurethane (PU) surface and the effect of the flange to stem ratio and biomechanical compliance on the fixation and stabilization of the percutaneous devices have been investigated.(20)... 

There are a number of strains of BoTx. They act by preventing the formation of vesicles containing ACh which leads to reduced release. This in turn means that insufficient ACh is released with the arrival of a nerve impulse to ensure that a post-junctional electric impulse will be generated and therefore synaptic transmission becomes blocked. The most striking consequence of this is a descending neuromuscular paralysis which may be life-threatening due to the effects on the respiratory muscles. At the autonomic level, prodromal symptoms such as dry mouth are related to synaptic block. The toxidromes produced by BoTx are considered in Chap. 7. The most important clinical consequence of the pathophysiology of the toxin is the production of a potentially fatal respiratory failure and arrest. More information about BoTx will be found in Chap. 11. 

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