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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.
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 .
The output neurons of the nucleus accumbens send axonal projections to the basal ganglia and the ventral analog of the globus pallidus, known as the ventral pallidum (VP). ). The VP, in turn, projects to the medial dorsal nucleus of the dorsal thalamus, which projects to the prefrontal cortex as well as back to the ventral and to dorsal stri
The projections from dopamine D1 receptors containing medium spiny neurons in the caudate nucleus and putamen synapse onto tonically active GABAergic cells in the substantia nigra pars reticulata and the internal segment of the globus pallidus (GPi), which then project to the thalamus. Because the striatonigral / striatoentopeduncular and ...
The interneurons found in the stratum lucidum are of two classes, spiny and aspiny. Spiny neurons are a "special type of inhibitory cell", characterized by spiny projections on the dendrites of the cell. The axons of these neurons in the hippocampus terminate primarily in the stratum lucidum and stratum radiatum of CA3.
Dendritic spines on medium spiny neuron of striatum. Types of cells in the striatum include: Medium spiny neurons (MSNs), which are the principal neurons of the striatum. [2] They are GABAergic and, thus, are classified as inhibitory neurons. Medium spiny projection neurons comprise 95% of the total neuronal population of the human striatum. [2]
The mesolimbic pathway and a specific set of the pathway's output neurons (e.g. D1-type medium spiny neurons within the nucleus accumbens) play a central role in the neurobiology of addiction. [20] [21] [22] Drug addiction is an illness caused by habitual substance use that induces chemical changes in the brain's circuitry. [23]
A dendritic spine (or spine) is a small membrane protrusion from a neuron's dendrite that typically receives input from a single axon at the synapse.Dendritic spines serve as a storage site for synaptic strength and help transmit electrical signals to the neuron's cell body.