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Interneurons can be further broken down into two groups: local interneurons and relay interneurons. [4] Local interneurons have short axons and form circuits with nearby neurons to analyze small pieces of information. [5] Relay interneurons have long axons and connect circuits of neurons in one region of the brain with those in other regions ...
Neurons are the excitable cells of the brain that function by communicating with other neurons and interneurons (via synapses), in neural circuits and larger brain networks. The two main neuronal classes in the cerebral cortex are excitatory projection neurons (around 70-80%) and inhibitory interneurons (around 20–30%). [2]
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. [3] While Betz cells have one apical dendrite typical of pyramidal neurons, they have more primary dendritic shafts, which can branch out at almost any point from the soma (cell body). [4]
Each of these interneuron class can be further divided into diverse subpopulations of neurons with distinct neurotransmitter phenotype, axonal projection and function during locomotion. [38] For example, V2 interneurons are ipsilaterally projecting that can be further classified as excitatory V2a and inhibitory V2b.
Primary motor cortex is defined anatomically as the region of cortex that contains large neurons known as Betz cells, which, along with other cortical neurons, send long axons down the spinal cord to synapse onto the interneuron circuitry of the spinal cord and also directly onto the alpha motor neurons in the spinal cord which connect to the ...
Projection fibers consist of efferent and afferent fibers uniting the cortex with the lower parts of the brain and with the spinal cord.In human neuroanatomy, bundles of axons (nerve fibers) called nerve tracts, within the brain, can be categorized by their function into association tracts, projection tracts, and commissural tracts.
Motor neurons receive signals from the brain and spinal cord to control everything from muscle contractions [3] to glandular output. Interneurons connect neurons to other neurons within the same region of the brain or spinal cord. When multiple neurons are functionally connected together, they form what is called a neural circuit.
The medium spiny neurons are medium-sized projection neurons with extensively branched dendrites. The cell body is 15–18 μm and has five primary dendrites that become branched. At first the dendrites are without spines but at about the first branch point they become densely spined.