You are an intern working in the Atlanta, GA office of Dr. Priya Wayne, MD. Dr.

Question

You are an intern working in the Atlanta, GA office of Dr. Priya Wayne, MD. Dr. Wayne is a specialist in rare neuromuscular and musculoskeletal disorders. You’ve been working with Dr. Wayne for the last year and due to this experience you’ve gained a great deal of knowledge about the human body and muscle physiology. You’re also a college student and working with Dr. Wayne has allowed you to gain first-hand experience with some of the material that you’re learning in your human physiology course. Just last week you had to turn in an assignment comparing and contrasting disorders of the neuromuscular junction. Today a group of high school students is coming for a tour and Dr. Wayne has asked you to prepare some information about muscles to present to the students. Specifically, Dr. Wayne has asked you to discuss the neuromuscular junction (NMJ), skeletal muscle contraction, and explain some of the issues that can occur when signaling between neurons and muscles does not go as planned.

Explanation / Answer

Neuromuscular junction (or myoneural junction) is a chemical synapse that is formed by the contact between a motor neuron and a muscle fiber.It is at this neuromuscular junction that a motor neuron is able to transmit a signal to the muscle fiber, causing muscle contraction.

Motor neurons release acetylcholine (ACh), a small molecule neurotransmitter, which diffuses across the synaptic cleft and binds to nicotinic acetylcholine receptors (nAChRs) on the cell membrane of the muscle fiber, also known as the sarcolemma. These are ionotropic receptors. The binding of ACh to the receptor can depolarize the muscle fiber, causing a cascade that eventually results in muscle contraction.
Any disorder that compromises the synaptic transmission between a motor neuron and a muscle cell is categorized under the term of neuromuscular diseases. These disorders can be inherited or acquired,most of these disorders tend to be caused by mutations or autoimmune disorders.
Neuromuscular junction diseases are a result of a malfunction in one or more steps of the pathway. As a result, normal functioning can be completely or partially inhibited, with the symptoms largely presenting themselves as problems in mobility and muscle contraction as expected from disorders in motor end plates. Thus neuromuscular junction diseases can also be referred to as end plate disorders.

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