MEDICAL PHYSIOLOGY

Detailed explanation-1: -As a rule, the synthesis of small-molecule neurotransmitters occurs within presynaptic terminals (Figure 6.6B). The enzymes needed for transmitter synthesis are synthesized in the neuronal cell body and transported to the nerve terminal cytoplasm at 0.5–5 millimeters a day by a mechanism called slow axonal transport.

Detailed explanation-2: -Neurotransmitters are located in a part of the neuron called the axon terminal. They’re stored within thin-walled sacs called synaptic vesicles.

Detailed explanation-3: -Small-molecule neurotransmitters are synthesized locally within the axon terminal. Some of the precursors necessary for the synthesis of these molecules are taken up by selective transporters on the membrane of the terminal.

Detailed explanation-4: -Therefore, unlike the other small molecule neurotransmitters, norepinephrine is synthesized within the vesicles, not in the cytoplasm. Like dopamine, the rate limiting step of this synthesis pathway is the activity of tyrosine hydroxylase.

Detailed explanation-5: -Neurotransmitters are generally synthesized in neurons and are made up of, or derived from, precursor molecules that are found abundantly in the cell. Classes of neurotransmitters include amino acids, monoamines, and peptides. Monoamines are synthesized by altering a single amino acid.