Search results
Results From The WOW.Com Content Network
Grey matter, or gray matter in American English, 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.
There are many small variations in the secondary and tertiary folds. [20] The outer part of the cerebrum is the cerebral cortex, made up of grey matter arranged in layers. It is 2 to 4 millimetres (0.079 to 0.157 in) thick, and deeply folded to give a convoluted appearance. [21] Beneath the cortex is the cerebral white matter.
Embedded within the white matter—which is sometimes called the arbor vitae (tree of life) because of its branched, tree-like appearance in cross-section—are four deep cerebellar nuclei, composed of gray matter. [14] Connecting the cerebellum to different parts of the nervous system are three paired cerebellar peduncles.
The brain is small and simple in some species, such as nematode worms; in other species, such as vertebrates, it is a large and very complex organ. [4] Some types of worms, such as leeches , also have an enlarged ganglion at the back end of the nerve cord, known as a "tail brain".
The large paired and convoluted lobes found in humans are typical of mammals, but the cerebellum is generally a single median lobe in other groups, and is either smooth or only slightly grooved. In mammals, the neocerebellum is the major part of the cerebellum by mass, but in other vertebrates, it is typically the spinocerebellum.
The cerebrum is made up of the two cerebral hemispheres and their cerebral cortices (the outer layers of grey matter), and the underlying regions of white matter. [2] Its subcortical structures include the hippocampus, basal ganglia and olfactory bulb.
White matter is composed of myelinated axons, fibrous astrocytes, myelinating oligodendrocytes, and microglia. In the peripheral nervous system: [12] Ganglion tissue is composed of cell bodies, dendrites, and satellite glial cells. Nerves are composed of myelinated and unmyelinated axons, Schwann cells surrounded by connective tissue.
The striatum (pl.: striata) or corpus striatum [5] is a cluster of interconnected nuclei that make up the largest structure of the subcortical basal ganglia. [6] The striatum is a critical component of the motor and reward systems; receives glutamatergic and dopaminergic inputs from different sources; and serves as the primary input to the rest of the basal ganglia.