Neural pathway
In neuroanatomy, a neural pathway is the connection formed by axons that project from neurons to make synapses onto neurons in another location, to enable neurotransmission (the sending of a signal from one region of the nervous system to another). Neurons are connected by a single axon, or by a bundle of axons known as a nerve tract, or fasciculus.[1] Shorter neural pathways are found within grey matter in the brain, whereas longer projections, made up of myelinated axons, constitute white matter.
In the hippocampus, there are neural pathways involved in its circuitry including the perforant pathway, that provides a connectional route from the entorhinal cortex[2] to all fields of the hippocampal formation, including the dentate gyrus, all CA fields (including CA1),[3] and the subiculum.
Descending motor pathways of the pyramidal tracts travel from the cerebral cortex to the brainstem or lower spinal cord.[4][5] Ascending sensory tracts in the dorsal column–medial lemniscus pathway (DCML) carry information from the periphery to the cortex of the brain.
Naming
The first named pathways are evident to the naked eye even in a poorly preserved brain, and were named by the great anatomists of the Renaissance using cadaver material.[citation needed] Examples of these include the great commissures of the brain such as the corpus callosum (Latin, "hard body"; not to be confused with the Latin word "colossus" – the "huge" statue), anterior commissure, and posterior commissure.[citation needed] Further examples include the pyramidal tract, crus cerebri (Latin, "leg of the brain"), and cerebellar peduncles (Latin, "little foot of the cerebellum").[citation needed] Note that these names describe the appearance of a structure but give no information on its function, location, etc.[citation needed]
Later, as neuroanatomical knowledge became more sophisticated, the trend was toward naming pathways by their origin and termination.[citation needed] For example, the nigrostriatal pathway runs from the substantia nigra (Latin, "black substance") to the corpus striatum (Latin, "striped body").[citation needed] This naming can extend to include any number of structures in a pathway, such that the cerebellorubrothalamocortical pathway originates in the cerebellum, synapses in the red nucleus ("ruber" in Latin), on to the thalamus, and finally terminating in the cerebral cortex.[citation needed]
Sometimes, these two naming conventions coexist. For example, the name "
In the cerebellum, one of the two major pathways is that of the mossy fibers. Mossy fibers project directly to the deep nuclei, but also give rise to the following pathway: mossy fibers → granule cells → parallel fibers → Purkinje cells → deep nuclei. The other main pathway is from the climbing fibers and these project to Purkinje cells and also send collaterals directly to the deep nuclei.[6]
Functional aspects
In general, neurons receive information either at their dendrites or cell bodies. The axon of a nerve cell is, in general, responsible for transmitting information over a relatively long distance. Therefore, most neural pathways are made up of axons.[citation needed] If the axons have myelin sheaths, then the pathway appears bright white because myelin is primarily lipid.[citation needed] If most or all of the axons lack myelin sheaths (i.e., are unmyelinated), then the pathway will appear a darker beige color, which is generally called grey.[citation needed]
Some neurons are responsible for conveying information over long distances. For example,
Basal ganglia pathways and dopamine
Neural pathways in the
Major neural pathways
- Arcuate fasciculus
- Cerebral peduncle
- Corpus callosum
- Pyramidal tracts – corticospinal and corticobulbar tracts
- Medial forebrain bundle
- Dorsal column–medial lemniscus pathway
- Retinohypothalamic tract is a photic neural input pathway involved in the circadian rhythms
See also
- Direct pathway of movement
- Indirect pathway of movement
- Reflex arc
- Systems neuroscience
- Nerve tract
- Neural circuit
- Nerve plexus
References
- ISBN 0-7817-3639-0.
A bundle of nerve fibers (axons) connecting neighboring or distant nuclei of the CNS is a tract.
- S2CID 25432455.
- PMID 18313770.
- ISBN 9780878936953.
- ^ Purves, Dale; Augustine, George J.; Fitzpatrick, David; Katz, Lawrence C.; LaMantia, Anthony-Samuel; McNamara, James O.; Williams, S. Mark (1 January 2001). Damage to Descending Motor Pathways: The Upper Motor Neuron Syndrome. Sinauer Associates.
- ISBN 0-19-515955-1.
- ^ PMID 24367324.