Final answer:
Curare is a generic term for arrow poisons from South America, primarily containing d-tubocurarine, which causes muscle relaxation and paralysis by blocking the action of acetylcholine at the neuromuscular junction.
Step-by-step explanation:
Curare is a term that refers to a variety of arrow poisons originating from South America. Its main active ingredient is d-tubocurarine, a compound known for its ability to induce muscle relaxation and paralysis. Curare was originally used by indigenous peoples for hunting, applying it to the tips of their arrows to quickly immobilize prey.
When it comes to its mode of action, d-tubocurarine works by competitively blocking the transmitter action of acetylcholine at the neuromuscular junction. By doing so, it prevents muscle contraction since acetylcholine release is crucial for this process. Despite this blockage, the muscle fiber's sensitivity to potassium ions remains unaltered, as well as its ability to respond to direct electrical stimulation. Therefore, although curare inhibits voluntary muscle movement, it doesn't affect the muscle's overall responsiveness to certain stimuli.