Final answer:
Glial cells, which make up about 10% of the brain, include various types such as astrocytes and oligodendrocytes, perform critical functions including neurotransmitter regulation and myelin production.
Step-by-step explanation:
The type of cell that makes up approximately 10% of the brain consists of specialized cells known as glial cells or neuroglia. These cells, often thought of as the 'glue' of the nervous system, perform a variety of functions essential for the health and operation of the brain. Among these glial cells, we find astrocytes, which have critical roles including the regulation of ion concentration, neurotransmitter uptake and breakdown, and the establishment of the blood-brain barrier. Additionally, oligodendrocytes produce the myelin for neurons in the central nervous system (CNS), essential for fast signal transmission. The brain also consists of microglia, which act as defenders against infection, and ependymal cells, which aid in producing cerebrospinal fluid as part of the brain's circulating fluid system.