Ligand gated means controlled by the or signal molecule. If the door is closed, certain are blocked from entering the cell. When the or signal molecule is attached, the door is open for certain to enter the cell. These types of receptors are important in the .

ligand; molecule; ligand; molecule; nervous system

Explanation:

Ligand-gated ion channels are membrane proteins that interact with ligands (molecules) and open in response to this binding. In the nervous system, these channels are activated by neurotransmitters (ligands) that regulate synaptic transmission between nerve cells (neurons). Neurotransmitters are signaling molecules clustered close to the cell membrane of axon terminals in presynaptic neurons. For example, glutamate is a ligand neurotransmitter that binds to ion channels and thus stimulates synaptic activity in the mammalian brain.

the answer is g1

answer: land bridge theory. land bridge theory held that shifting portions of dry land explained the finding of identical species on different continents. plate tectonic theory eventually eliminated the land bridge theory.