[Answer] What is the neuromuscular junction?

Answer: point of contact between a motor neuron and a skeletal muscle cell
What is the neuromuscular junction?

Neuromuscular junction – Wikipedia

Neuromuscular junction disease – Wikipedia

Neuromuscular disease – Wikipedia

Neuromuscular disease – Wikipedia

A neuromuscular junction (or myoneural junction) is a chemical synapse between a motor neuron and a muscle fiber. It allows the motor neuron to transmit a signal to the muscle fiber causing muscle contraction. Muscles require innervation to function—and even just to maintain muscle tone avoiding atrophy. In the neuromuscular system nerves from the central nervous system and the periphe…

A neuromuscular junction (or myoneural junction) is a chemical synapse between a motor neuron and a muscle fiber. It allows the motor neuron to transmit a signal to the muscle fiber causing muscle contraction. Muscles require innervation to function—and even just to maintain muscle tone avoiding atrophy. In the neuromuscular system nerves from the central nervous system and the peripheral nervous system are linked and work together with muscles. Synaptic transmission at the neuromuscular junction begins when an action potential reaches the presynaptic terminal of a motor neuron which activates voltage-gated calcium channels to allow calcium ions to enter the neuron. Calcium ions bind to sensor proteins (synaptotagmin) on synaptic vesicles triggering vesicle fusion with the cell membrane and subsequent neurotransmitter release from the motor neuron into the synaptic cleft. In vertebrates 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. nAChRs are ionotropic receptors meaning they serve as ligand-gated ion channels. The binding of ACh to the receptor can depolarize the muscle fiber causing a cascade that eventually results in muscle contraction. Neuromuscular junction diseases can be of genetic and autoimmune origin. Genetic disorders such as Duchenne muscular dystrophy can arise from mutated structural proteins that comprise the neuromuscular junction whereas autoimmune diseases such as myasthenia gravis occur when antibodies are produced against nicotinic acetylcholine receptors on the sarcolemma.

Quantal transmission At the neuromuscular junction presynaptic motor axons terminate 30 nanometers from the cell membrane or sarcolemma of a muscle fiber. The sarcolemma at the junction has invaginations called postjunctional folds which increase its surface area facing the synaptic cleft. These postjunctional folds form …

Quantal transmission At the neuromuscular junction presynaptic motor axons terminate 30 nanometers from the cell membrane or sarcolemma of a muscle fiber. The sarcolemma at the junction has invaginations called postjunctional folds which increase its surface area facing the synaptic cleft. These postjunctional folds form the motor endplate which is studded with nicotinic acetylcholine receptors (nAChRs) at a density of 10 000 receptors/micrometer . The presynaptic axons terminate in bulges called terminal boutons (or presynaptic terminals) that project toward the postjunctional folds of the sarcolemma. In the frog each motor nerve terminal contains about 300 000 vesicles with an average diameter of 0.05 micrometers. The vesicles contain acetylcholine. Some of these vesicles are gathered into groups of fifty positioned at active zones close to the nerve membrane. Active zones are about 1 microm…

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