Final answer:
The correct answer is Ligand-Gated Channels, which open due to the binding of a neurotransmitter and are essential in transmitting electrical signals in the nervous system.
Step-by-step explanation:
The channels that open when a neurotransmitter binds to a receptor site are c) Ligand-Gated Channels.
Ligand-gated channels are specialized protein structures embedded in the cell membrane that open to allow the passage of ions into or out of cells when a specific signaling molecule, or ligand such as a neurotransmitter, attaches to them. This binding event changes the shape of the channel protein, resulting in an open pore that permits ions to flow across the cell membrane.
These channels are crucial in neural communication and play an important role in the transmission of electrical signals across synapses. A common example is the acetylcholine receptor at neuromuscular junctions, which, when acetylcholine binds, allows Na+, Ca+, and K+ ions to pass through the membrane, causing depolarization.