Final answer:
Neurotransmitters are deactivated and removed from the synaptic cleft through diffusion, enzymatic degradation, and reuptake, allowing the synaptic cleft to reset for new signals.
Step-by-step explanation:
After a neurotransmitter has facilitated a signal across the synaptic cleft, it is essential to deactivate and remove it to reset the synapse for the next signal. This deactivation can occur in three main ways:
- Diffusion: The neurotransmitter merely drifts away from the synaptic cleft.
- Enzymatic degradation: Specific enzymes break down the neurotransmitter into inactive substances. For instance, acetylcholine is broken down by the enzyme acetylcholinesterase.
- Reuptake: The presynaptic neuron reabsorbs the neurotransmitter, clearing the synaptic cleft.
These processes ensure the precise control of neurotransmission, allowing the postsynaptic neuron to return to its resting state, prepared for the next wave of communication.