Betz cells (also known as pyramidal cells of Betz) are giant

pyramidal cells Pyramidal cells, or pyramidal neurons, are a type of multipolar neuron found in areas of the brain including the cerebral cortex, the hippocampus, and the amygdala. Pyramidal neurons are the primary excitation units of the mammalian prefrontal cor ...

( neurons) located within the fifth layer of the

grey matter Grey matter is a major component of the central nervous system, consisting of neuronal cell bodies, neuropil (dendrites and unmyelinated axons), glial cells (astrocytes and oligodendrocytes), synapses, and capillaries. Grey matter is distingu ...

in the primary motor cortex. These neurons are the largest in the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...

, sometimes reaching 100 μm in diameter.Nolte, J. ''The Human Brain'', 5th ed. Mosby: Missouri; 2002, p.527. Betz cells are

upper motor neuron Upper motor neurons (UMNs) is a term introduced by William Gowers in 1886. They are found in the cerebral cortex and brainstem and carry information down to activate interneurons and lower motor neurons, which in turn directly signal muscles t ...

s that send their

axon An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action p ...

s down to the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the sp ...

via the

corticospinal The pyramidal tracts include both the corticobulbar tract and the corticospinal tract. These are aggregations of efferent nerve fibers from the upper motor neurons that travel from the cerebral cortex and terminate either in the brainstem (''co ...

tract, where in

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s they synapse directly with anterior horn cells, which in turn synapse directly with their target muscles. Betz cells are not the sole source of direct connections to those neurons because most of the direct corticomotorneuronal cells are medium or small neurons. While Betz cells have one

apical dendrite An apical dendrite is a dendrite that emerges from the apex of a pyramidal cell. Apical dendrites are one of two primary categories of dendrites, and they distinguish the pyramidal cells from spiny stellate cells in the cortices. Pyramidal cells are ...

typical of pyramidal neurons, they have more primary dendritic shafts, which can branch out at almost any point from the

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(cell body). These perisomatic (around the cell body) and basal dendrites project into all cortical layers, but most of their horizontal branches/arbors populate layers V and VI, some reaching down into the

white matter White matter refers to areas of the central nervous system (CNS) that are mainly made up of myelinated axons, also called tracts. Long thought to be passive tissue, white matter affects learning and brain functions, modulating the distributi ...

. According to one study, Betz cells represent about 10% of the total pyramidal cell population in layer Vb of the human primary motor cortex. Betz cells are named after Ukrainian scientist Volodymyr Betz, who described them in his work published in 1874.Betz W. (1874) ''Anatomischer Nachweis zweier Gehirncentra.'' Centralblatt für die medizinischen Wissenschaften. 12:578-580, 595-599.

Notes

External links

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{{Cortex types Cerebral cortex Human cells Motor system