Nervous tissue (overview)
Textus nervosus
Also known as: neural tissue, neurons and glia, neuroglia, grey matter, white matter
Tissue of neurons, which generate and conduct electrical signals and communicate at synapses, and the more numerous supporting neuroglia; it forms the brain, spinal cord, ganglia and nerves.
Overview
Neurons are excitable cells with a cell body (soma, perikaryon) containing the nucleus and Nissl substance (RER), dendrites that receive input, and usually a single axon that conducts action potentials to synapses on other neurons, muscle or gland cells. Most are permanent, post-mitotic cells. The human brain contains ≈86 billion neurons and a similar number of glial cells (the old "10 glia per neuron" figure is an overestimate).
Neuroglia support, insulate and protect neurons. In the CNS: astrocytes (blood–brain barrier support, K⁺ and neurotransmitter buffering, scar formation; GFAP-positive), oligodendrocytes (myelinate several CNS axons each), microglia (resident macrophages, derived from yolk-sac precursors) and ependymal cells (line ventricles and central canal; ciliated). In the PNS: Schwann cells (each myelinates one segment of one axon, or ensheathes several unmyelinated axons) and satellite cells (surround neuronal cell bodies in ganglia).
In the CNS, grey matter contains neuronal cell bodies, dendrites, unmyelinated axons, synapses and glia; white matter consists mainly of myelinated axon tracts (white because of myelin lipid). In the PNS, axons are bundled into nerves by endoneurium, perineurium and epineurium. Nervous tissue is detailed in the Nervous system.
Parts & subdivisions
- Signalling cell — soma, dendrites, axon.
- Star-shaped CNS glia.
- CNS myelinating cell.
- CNS immune cells.
- Lines ventricles; CSF.
- PNS myelinating cell.
- Site of neuronal communication.
Anatomy
- Development
Neurons and macroglia derive from neuroectoderm: the neural tube forms the CNS; the neural crest forms sensory and autonomic ganglia, Schwann cells and satellite cells. Microglia come from yolk-sac mesoderm.
Function
- Receives, integrates and transmits information.
- Controls muscles and glands; maintains homeostasis with the endocrine system.
- Underlies sensation, cognition, memory and behaviour.
Clinical significance
Glial tumours and demyelination
Most primary brain tumours of adults arise from glia (glioblastoma — astrocytic, GFAP-positive). Multiple sclerosis destroys CNS myelin (oligodendrocytes); Guillain–Barré syndrome attacks peripheral myelin (Schwann cells).
Limited regeneration
CNS neurons cannot divide and their axons regenerate poorly (inhibitory myelin proteins, glial scar); peripheral axons can regrow ≈1–3 mm/day along Schwann-cell tubes if the endoneurium is intact.
Compiled from standard anatomy and physiology references — see the Cells & Tissues sources. For education only; not medical advice.