What happens to the neurotransmitters that are released in excess and remain unused?

When neurotransmitters are released in excess and remain unused, several things can happen:

1. Reuptake: This is the most common way the brain gets rid of excess neurotransmitters. In this process, the neurotransmitter is reabsorbed back into the neuron that released it. This helps to regulate the levels of neurotransmitters in the synaptic cleft (the space between neurons where neurotransmitters are released).

2. Enzyme Degradation: Some neurotransmitters are broken down by enzymes. For example, the enzyme acetylcholinesterase breaks down the neurotransmitter acetylcholine in the synaptic cleft.

3. Diffusion: Some neurotransmitters simply drift away, out of the synaptic cleft, and are no longer in a position to have an effect.

4. Glial Cells: These cells, which are found throughout the brain and spinal cord, can also absorb neurotransmitters.

These processes help to ensure that neurotransmitters do not overstimulate the brain and body, maintaining a balanced and well-regulated system of communication within the brain.