Final answer:
c. Either answer is correct. Neurotransmitters are either degraded by enzymes or reabsorbed by the presynaptic neuron through a process known as reuptake, making 'c. Either answer is correct' the correct answer to the question regarding what happens to neurotransmitters after they deliver their message.
Step-by-step explanation:
After neurotransmitters deliver their message to the receiving neuron, there are several events that can occur to remove these chemicals from the synaptic cleft. One such event is that neurotransmitters may be degraded by enzymes in the synaptic cleft. Another significant process is reuptake, where neurotransmitters are taken back into the axon terminals of the sending neuron for potential reuse. Thus, the correct answer to what happens to neurotransmitters after they have transmitted their signal is either they are broken down by enzymes, or they are reabsorbed by the presynaptic neuron. Therefore, the answer to the question is 'c. Either answer is correct.'
In the brain, neurotransmitter reuptake is a crucial process that helps regulate the levels of neurotransmitters available in the synaptic cleft and ensures that neurons are ready to fire again. This management of neurotransmitter levels is essential to maintain the balance and proper functioning of the nervous system. Various drugs target these mechanisms, such as those provided for Alzheimer's patients that block the action of acetylcholinesterase, consequently increasing neurotransmission by preventing acetylcholine degradation.