Answer:
ligand; ions; ligand; ions; nervous system
Explanation:
Ligand-gated ion channels are transmembrane protein complexes that open when they bind to their corresponding ligands (e.g., neurotransmitters). This type of receptor is known to modulate the synaptic transmission between neuron cells or neuron and muscle cells. In the nervous system, ligand-gated ion channels located at sites of synaptic contact determine the ion flow in response to neurotransmitter binding. Some examples of ligand-gated ion channels include gamma-aminobutyric acid A (GABA-A) and nicotinic cholinergic receptors.
