Ionotropic receptors are a type of membrane protein that function as channels for ions. When a specific neurotransmitter, such as glutamate or acetylcholine, binds to these receptors, they undergo a conformational change that opens the channel. This allows ions like sodium, potassium, or calcium to flow in or out of the cell, leading to rapid changes in the cell's electrical potential. These receptors play a crucial role in fast synaptic transmission in the nervous system. They are essential for processes such as muscle contraction and the transmission of signals between neurons. Ionotropic receptors are distinct from metabotropic receptors, which work through slower, indirect signaling pathways.