Brain cells make up the functional tissue of the brain. The rest of the brain tissue is the structural stroma that includes connective tissue such as the meninges, , and ducts. The two main types of cells in the brain are , also known as nerve cells, and , also known as neuroglia.
Neurons are the of the brain that function by communicating with other neurons and (via ), in and larger brain networks. The two main neuronal classes in the cerebral cortex are excitatory projection neurons (around 70-80%) and inhibitory interneurons (around 20–30%). Neurons are often grouped into a cluster known as a nucleus where they usually have roughly similar connections and functions.
Glia are the supporting cells of the neurons and have many functions of which not all are clearly understood, but include providing support and nutrients to the neurons. Glia are grouped into macroglia—, , and , and much smaller microglia which are the of the central nervous system. Astrocytes are seen to be capable of communication with neurons involving a signaling process similar to neurotransmission, called gliotransmission.
Cerebral cortex interneurons only make up around a fifth of the neuronal population but they play a major role in modulating cortical activity needed for cognition and many aspects of learning and memory. Cortical interneurons vary in shape, molecular make-up, and electrophysiology; they function collectively to maintain the balance between excitation and inhibition in the cortex primarily through the use of GABA. Disruption of this balance is a common feature of neuropsychiatric disorders such as schizophrenia. A cause of the disruption can occur in prenatal development through the exposure to chemicals and environment.
In the cerebral cortex different neurons occupy the different cortical layers and include the and . In the cerebellum and interneuronal Golgi cells predominate.
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