Basal forebrain
nuclei
Midbrain-pontine
nuclei
Figure 7.2. This medial view of the brain labels several clusters of cells known
to release acetylcholine as a neurotransmitter. The word nucleus here means
a cluster of nerve cells having a distinctive morphology. These clusters of
cholinergic cells are located beneath the cerebral cortex, at the base of the
forebrain (basal forebrain), and in the midbrain and pons of the brainstem.
Axons of the neurons in these nuclei innervate large regions of the brain.
Another group of neurotransmitters in the human brain are the
monoamines, so called because they possess an amine (nitrogen-
containing) group located at the end of a short chain of carbon atoms.
Serotonin, dopamine, norepinephrine, epinephrine, and histamine
represent this group of neurotransmitters. Serotonin, also called 5-
hydroxytryptamine or 5HT, is biosynthesized in two steps from the
amino acid tryptophan.