Physiology of the neuromuscular junction and related disorders

Abstract

The neuromuscular junction (NMJ) is a region of communication between the nerve and muscle cells. Non-anatomical functional contact occurs at this junction. The NMJ is divided into three regions: presynaptic, synaptic gap, and postsynaptic. When action potentials reach the terminal end of the nerve, acetylcholine (ACh) molecules in the presynaptic region are released into the synaptic gap. The released ACh stimulates nicotinic ACh receptors and depolarizes the motor endplate. This depolarization is transformed into actual action potential when a threshold value is surpassed. At this point, ACh in excess that required for neurotransmission is released. Subsequently, the ACh receptor is stimulated. The principal reason for excess production of ACh is to ensure a sufficient supply for neurotransmission. The NMJ is thought as a static structure. However, this structure has dynamic remodeling activity, which is significantly affected by drugs, toxins, aging, injury, and exercise. The net effect of pathologies involving the NMJ is to decrease the ability of neurotransmission. These pathologies can be congenital, acquired, or specific to presynaptic, synaptic, or postsynaptic regions. The etiological origins of NMJ pathologies include autoimmunity, congenital disease, pharmacological or toxic agents, and trauma. In this review, physiology and related disorders of the neuromuscular junction considered in the light of recent knowledge has been aimed.

Keywords

• Neural transmission disorders
• Neuromuscular blocking agents
• Neuromuscular junction
• Physiology

References

1. Amato, A.A., Russell, J.A., 2008. Disorders of neuromuscular transmission. In Neuromuscular Disorders, A.A. Amato and J.A. Russell, eds. The McGraw-Hill Companies, United. States, pp. 457-528.
2. Baker, D., 2009, Chemical and biological warfare agents: The role of the anesthesiologist In Miller’s Anesthesia, R.D. Miller, ed. Churchill Livingstone, United States, pp. 2333-2256.
3. Bittner, E.A., Martyn, J.A.J., 2013. Neuromuscular physiology and pharmacology. In Pharmacology and physiology for anesthesia foundations and clinical application, H.C. Hemmings and T.D. Egan, eds. Elsevier Saunders, United States, pp. 309-324.
4. Butterworth, J.F., Mackey, D.C., Wasnick J.D., 2013. Anesthesia for patients with neuromuscular disease. In Morgan and Mikhails Clinical Anesthesiology, J.F. Butterworth, D.C Mackey, and J.D. Wasnick, eds. McGraw-Hill Education, United States, pp. 747-758.
5. Cousin, M,T., 2013. History of anaesthesia: Who discovered the neuromuscular junction? The opposing views of Claude Bernard and Alfred Vulpian. Eur. J. Anaesthesiol. 30, 1-4.
6. Cross, M.E., Plunkett, E.V.E., 2008. Muscle structure and function. In physics, pharmacology and physiology for anaesthetists, M.E. Cross and E.V.E. Plunkett, eds. Cambridge University Press, England, pp. 188-190.
7. Deschenes, M.R., Tenny, K.A., Wilson, M. H., 2006. Increased and decreased activity elicits specific morphological adaptations of the neuromuscular junction. Neuroscience. 137, 1277-1283.
8. Glick, D.B., 2009. The autonomic nervous system. In Miller’s Anesthesia, R.D. Miller., ed. Churchill Livingstone, United States, pp. 261-304. Hines, R.L., Marschall, K.E., 2012. Psychiatric disease, substance abuse, and drug overdose. In Stoelting’s anesthesia and co-existıng disease, R.L. Hines and K.E. Marschall, eds., Elsevier Saunders, United States, pp. 533-557.

9. Martyn, J.A J., 2009. Neuromuscular physiology and pharmacology. In Miller’s Anesthesia, R.D. Miller, ed. Churchill Livingstone, United States, pp. 341-360.
10. Naguib, M., Lien, C.A., 2009. Pharmacology of muscle relaxants and their antagonists. In Miller’s anesthesia, R.D. Miller, ed. Churchill Livingstone, United States. 1, 859-912.
11. Ramani, R., 2012. Muscle and neuromuscular diseases. In Stoelting’s Anesthesia and Co-Existing Disease, R.L. Hines and K.E. Marschall, eds. Elsevier Saunders, United States, pp. 444-452.
12. Urban, M.K., 2012. Muscle diseases. In anesthesia and uncommon diseases, L.A. Fleisher, ed. Elsevier Saunders, United States, pp. 296-318. Widmaier, E.P., Raff, H., Strang, K.T., 2004. Muscle. In Vander, Sherman, Luciano’s human physiology: The mechanisms of body function, E.P. Widmaier, H. Raff, and K.T. Strang, eds. McGraw-Hill Higher Education, United States, pp. 267-310.
13. Wilson, M.H., Deschenesn M.R., 2005. The neuromuscular junction: Anatomical features and adaptations to various forms of increased, or decreased neuromuscular activity. Int. J. Neurosci. 115, 803-828.
14. Zhou, J., Allen, P.D., Pessah, I. N., Naguib, M., 2009. Neuromuscular disorders and malignant hyperthermia. In Miller’s Anesthesia, R.D., Miller, ed. Churchill Livingstone, United States, pp. 1171-1196.