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Overview of Neuromuscular Junction Disorders

(Disorders of Neuromuscular Transmission)


Michael Rubin

, MDCM, New York Presbyterian Hospital-Cornell Medical Center

Last full review/revision Dec 2020| Content last modified Dec 2020
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Nerves Overview of the Peripheral Nervous System The peripheral nervous system refers to the parts of the nervous system that are outside the central nervous system, that is, those outside the brain and spinal cord. Thus, the peripheral nervous... read more connect with muscles at the neuromuscular junction. There, the ends of nerve fibers connect to special sites on the muscle’s membrane called motor end plates. These plates contain receptors that enable the muscle to respond to acetylcholine, a chemical messenger (neurotransmitter) released by the nerve to transmit a nerve impulse across the neuromuscular junction. After a nerve stimulates a muscle at this junction, an electrical impulse flows through the muscle, causing it to contract. After transmitting the impulse, acetylcholine is broken down so that it does not continue to stimulate the muscle.

Did You Know...

  • Nerve gases used in chemical warfare interfere with communication between nerves and muscles.

Disorders in which the neuromuscular junction malfunctions include

In addition, many drugs can cause the neuromuscular junction to malfunction. These drugs include very high doses of some antibiotics, certain insecticides Insecticide Poisoning Many insecticides can cause poisoning after being swallowed, inhaled, or absorbed through the skin. Symptoms may include eye tearing, coughing, heart problems, and breathing difficulties. The... read more (organophosphates), chemical-warfare agents (such as sarin gas and Novichok), and curare. Novichok was developed in Russia and has been used in assassination attempts. Curare has been used to help relax muscles during surgery and to paralyze and kill when placed on the tip of poison darts. Some of these substances prevent the normal breakdown of acetylcholine after the nerve impulse has been transmitted to the muscle.

Neuromuscular junction disorders typically decrease nerve cell activity and cause muscle weakness. But they do not affect sensation (that is, they do not cause loss of sensation or abnormal sensations, such as tingling or a pins-and-needle sensation).

Some neuromuscular junction disorders decrease the nerve's activity, causing weakness. Other disorders, such as the following, increase the nerve's activity:

Although the changes that cause stiff-person syndrome originate mainly in the brain and spinal cord (the central nervous system), they also affect the neuromuscular junction. The result is continuous stimulation and contraction of muscles.

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Test your knowledge

Bell Palsy
Bell palsy is sudden weakness or paralysis of the muscles on one side of the face due to malfunction of the seventh cranial nerve. This nerve moves facial muscles, stimulates salivary and tear glands, detects tastes, and controls a muscle involved in hearing. Which of the following is often the first symptom of Bell palsy?
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