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. © 2014 OMU