Cell Types
Neural cells
6
Astrocytes
Astrocytes are star-shaped glial cells, the most abundant in the central nervous system (CNS). They are vital for homeostasis: they form part of the blood-brain barrier, regulate blood flow, control extracellular ion/neurotransmitter balance (e.g., glutamate uptake), and provide metabolic support to neurons. Through the "tripartite synapse," they modulate synaptic strength and plasticity. They also respond to injury via reactive astrogliosis, playing dual roles in scar formation and neuroprotection.
Excitatory neurons
Excitatory neurons are nerve cells that, when activated, increase the likelihood of their target neuron firing an action potential. They primarily release the neurotransmitter glutamate at their synapses. They form the primary driving force in neural circuits throughout the brain (e.g., cortical pyramidal neurons) and are fundamental for information propagation, synaptic plasticity (like LTP), and processes such as learning, memory, and cognition.
Inhibitory neurons
Inhibitory neurons reduce the probability of their postsynaptic target neuron firing an action potential. They primarily release the neurotransmitters GABA (in the brain) or glycine (in the spinal cord/brainstem). They are crucial for balancing neural circuit activity, preventing runaway excitation, generating rhythmic outputs (e.g., in pacemaker circuits), and shaping the temporal and spatial precision of neural computations. Types include interneurons like basket cells and Purkinje cells.
Oligodendrocyte progenitor cells
Oligodendrocyte progenitor cells (OPCs), also called NG2-glia, are a population of glial cells found throughout the CNS. They are proliferative and maintain the capacity to differentiate into mature, myelinating oligodendrocytes. OPCs are critical for developmental myelination and remain in the adult CNS, where they contribute to remyelination after demyelinating injuries (e.g., in Multiple Sclerosis) and may have additional roles in monitoring neural circuits.
Oligodendrocytes
Oligodendrocytes are the myelinating glial cells of the central nervous system (CNS). Each oligodendrocyte extends multiple processes to wrap and insulate segments of several different axons with concentric layers of myelin membrane. This myelin sheath greatly increases the speed of action potential propagation (saltatory conduction). They also provide metabolic support to the axons they enwrap. Loss of oligodendrocytes or myelin disrupts nerve signaling.
Microglia
Microglia are the resident macrophages and primary immune cells of the central nervous system (CNS). In their resting state, they constantly survey the parenchyma. Upon detecting injury, infection, or pathological signals, they activate, becoming phagocytic to clear debris, dead cells, and pathogens. They also play essential roles in synaptic pruning during development, modulating neuroinflammation, and can contribute to both repair and neurodegeneration in diseases.
Epithelial cells
2
Choroid plexus
The choroid plexus is a specialized structure in the brain's ventricles composed of a network of capillaries surrounded by a monolayer of modified epithelial cells (choroid plexus epithelial cells). Its primary function is to produce cerebrospinal fluid (CSF) by filtering blood plasma and actively secreting ions and water. It also forms the blood-CSF barrier and secretes growth factors and signaling molecules into the CSF.
Gonadotropes
Gonadotropes are endocrine cells in the anterior pituitary gland that produce and secrete the gonadotropins: follicle-stimulating hormone (FSH) and luteinizing hormone (LH). In response to gonadotropin-releasing hormone (GnRH) from the hypothalamus, they release these hormones into the bloodstream. FSH and LH then act on the gonads (ovaries and testes) to regulate gametogenesis and sex steroid hormone production.