Projection fiber

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Projection fiber

Details

Identifiers

Latin

"Triple Cartridge Respirator" by?T Doolen

?

Fibrae projectionis

NeuroNames

1218

TA98

A14.1.00.018

TA2

5617

FMA

76745

Anatomical terms of neuroanatomy

[edit on Wikidata]

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?tracts, within the brain, can be categorized by their function into?association fibers, projection fibers, and?commissural fibers.[1]

In the?neocortex,?projection neurons?are excitatory neurons that send axons to distant brain targets.[2]?Considering the six histologically-distinct layers of the neocortex,?associative projection neurons?extend axons within one cortical hemisphere;?commissural projection neurons?extend axons across the midline to the contralateral hemisphere; and?corticofugal projection neurons?extend axons away from cortex.

（這意味著同一小片皮層同時(shí)是associative projection、commissural projection、corticofugal projection。）

[2]?That said, some neurons are multi-functional and can therefore be categorized into more than one such category.[2]

Contents

·?1Efferent

·?2Afferent

·?3References

·?4External links

Efferent[edit]

The principal?efferent fibers?are:

·?(1) the?motor tract, occupying the?genu?and anterior two-thirds of the?occipital part of the internal capsule, and consisting of

o?(a) the?geniculate fibers, which?decussate?in the medulla, and end in the?motor nuclei?of the?cranial nerves?of the opposite side; and

o?(b) the?cerebrospinal fibers, which are prolonged through the?medullary pyramids?into the?spinal cord:

·?(2) the?corticopontine fibers, ending in the?pontine nuclei.

（這里意味著來自于大腦皮層的軸突能夠直達(dá)pons。而在其他的詞條我們會(huì)發(fā)現(xiàn)orbital cortex投射到midbrain和pons，而orbital cortex通過uncinate long association fiber與polar temporal cortex連接，而polar temporal cortex通過inferior longitudinal long association fiber與occipital cortex連接。上述連接意味著：視覺信息進(jìn)入occipital cortex然后最終到達(dá)orbital cortex，從而直接影響midbrain和pons中核團(tuán)的活動(dòng)。這個(gè)機(jī)制對應(yīng)著一類人的感覺，尤其是在視覺信息是靜態(tài)狀態(tài)時(shí)，這個(gè)感覺使得該信息突出于背景信息，一旦信息動(dòng)起來，與背景信息相關(guān)聯(lián)，這個(gè)感覺就沒有了，因?yàn)槟愕淖⒁饬D(zhuǎn)移到其他的腦區(qū)功能，而不再維持上述通路。）

Afferent[edit]

The chief?afferent fibers?are:

·?(1) those of the?lemniscus?which are not interrupted in the?thalamus;

·?(2) those of the?superior cerebellar peduncle?which are not interrupted in the?red nucleus?and?thalamus;

·?(3) numerous fibers arising within the?thalamus, and passing through its stalks to the different parts of the?cortex;

·?(4) optic and?acoustic fibers, the former passing to the?occipital, the latter to the?temporal lobe.

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