Neuromuscular junction

A synapse where a motor neuron signals a skeletal muscle fiber. Its chemical transmission converts a nerve impulse into an electrical response in muscle.

Acetylcholine: A neurotransmitter released at neuromuscular junctions that activates receptors on skeletal muscle fibers. Motor neurons release it to carry the signal across the synaptic cleft.
Motor neuron: A neuron that carries commands from the central nervous system to muscles or glands. Its axon forms the presynaptic side of the junction.
Myasthenia gravis: An autoimmune disorder in which antibodies impair postsynaptic signaling at neuromuscular junctions. Reduced receptor function weakens the muscle response to nerve signals.
Claude Bernard: A French physiologist whose experiments helped establish the action of curare at the nerve–muscle interface. His curare studies helped localize paralysis to transmission rather than muscle contraction itself.
Electrical synapse: A cell-to-cell junction that transmits electrical current directly through gap junctions. Unlike the neuromuscular junction, it passes current without a neurotransmitter crossing a cleft.
Nicotinic acetylcholine receptor: A ligand-gated ion channel activated by acetylcholine. Its opening produces the end-plate current that initiates muscle excitation.
Skeletal muscle: Striated muscle tissue, usually attached to bones and controlled voluntarily. Its fibers receive the motor neuron’s signal at specialized synapses.
Lambert-Eaton myasthenic syndrome: An autoimmune disorder that impairs presynaptic calcium channels and acetylcholine release. It demonstrates how disrupting the nerve terminal weakens junctional transmission.
John Newport Langley: A British physiologist who developed the concept of receptive substances at cell surfaces. His work on nicotine and curare anticipated the receptor concept at the junction.
Chemical synapse: A junction where one cell signals another by releasing neurotransmitter molecules. The neuromuscular junction is a specialized chemical synapse with unusually reliable transmission.

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