Brain parenchyma is the tissue that makes the brain the brain as opposed to another organ, according to SIUC School of Medicine. It is the brain's nervous tissue, which consists of the nerve cells and the glia.
Nervous tissue is responsible for receiving and sending signals throughout the body, according to About.com. Neurons are cells that make up the nervous tissue. A neuron consists of a cell body made of cytoplasm that contains a nucleus, organelles. A neuron has projections that are either axons or dendrites. Axons take signals from the neuron, while dendrites bring signals to the neuron.
Most neurons only have one axon, though the axon can be branched, says About.com. The terminus of an axon is the synapse, which usually communicates with a dendrite. Dendrites are more numerous than axons, and also branched. A grouping of neurons are called nerves. Sensory nerves are made up exclusively of dendrites, while motor nerves are made of axons or axons and dendrites.
Glial cells do not transmit or receive signals, says About.com. These cells support and protect the nerve cells and repair damaged tissue. They protect the brain by blocking toxins from entering through the capillaries and remove waste. They also help create the myelin sheath that wrap around and protect most nerve cells. There are three basic types of glial cells: astrocytes, microglia and oligodendrocytes.