Neuromuscular junction (NJM).
A 30-year-old female presents with muscle weakness and fatigue. Abnormal electromyography testing and a positive increase in ACTH receptor test is reported. Her final diagnosis is Myasthenia Gravis.
Described the normal synaptic transmission at the neuromuscular junction (NJM).
To be able to understand how the neuromuscular junction works (NMJ) understanding what is normal to abnormal and the role of neurotransmitter in the generation of muscle contraction needs to be understood. The brain has several neurotransmitters including, acetylcholine, norepinephrine, dopamine, and serotonin the brain is an organ with millions of neurons and an extensive circuitry that allows receiving and transmitting signals from the environment in response to stimuli (Dlugasch & Story , 2021). Neurotransmitter modulators such as Acetylcholine receives signals from the cerebral cortex which then binds to nicotinic acetylcholine receptor on muscle cell membrane that resulted in muscle contraction (action potentials). The neuromuscular junction has three main parts; presynaptic membrane which is the membrane of an axon terminal, post synaptic membrane the membrane of the skeletal muscle also known as motor end plate, and synaptic cleft gap between pre and post synaptic membrane. Our brain sense a signal in the form of action potential from the cerebral cortex (upper motor neuron) this then activates the lower motor neuron through the axon terminals to the muscle fibers where innervation happen, the NMJ is the area where motor neuron meets the skeletal muscle fiber when the lower motor neuron is activated there is an influx of calcium ions into the presynaptic membrane followed by the release of acetylcholine into the synaptic cleft Acetylcholine binds to nicotinic receptors this leads to the generation of an action potential which eventually resulted in muscle contraction (Omar, Marwaha, & Bollu, 2021). Myasthenia Gravis is an immunologically mediated disorders affecting the end plate region of the postsynaptic neuromuscular junction, this is analogous to having a gatekeeper where an individual will be check (action potential) whether the command from the king/ authority (cerebral cortex) will be allowed to enter the kingdom (muscle contraction), any disturbances or discrepancy of information will disallow/inhibit the contraction.
