Finally, the chemical messenger is back into the presynaptic neuron, ready to be used again. as levels of the neurotransmitter in the synapse the stimulation of the postsynaptic nerve ends.

Finally, the chemical messenger is taken back into the presynaptic neuron, ready to be used again. As levels of the neurotransmitter in the synapse decrease, the stimulation of the postsynaptic nerve ends.

Explanation:

      The synapse is the space between two neurons. Through this space, neurons communicate.

      An action potential causes the release of neurotransmitters from the presynaptic neuron; if there are enough of these specific neurotransmitters to bind to receptors on the postsynaptic neuron, they do and an action potential is now generated on this neuron.

     This communication between two neurons must end once it's happened. In order for it to end, the synapse must be free of neurotransmitters. One mechanism to do so is for the neurotransmitters to be taken back into the presynaptic neuron.

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.