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Pyramidal cell

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Pyramidal cell

"Hippocampus CA1 Pyramidal Cell" by?JustasB

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A human?neocortical?pyramidal neuron?stained via?Golgi's method. The apical?dendrite?extends vertically above the?soma?(cell body) and the numerous basal dendrites radiate laterally from the base of the cell body.

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A reconstruction of a pyramidal cell. Soma and dendrites are labeled in red, axon arbor in blue. (1) Soma, (2) Basal dendrite, (3) Apical dendrite, (4) Axon, (5) Collateral axon.

Details

Location

Cerebral cortex?esp. Layers III and V

Shape

Multipolar Pyramidal

Function

excitatory projection neuron

Neurotransmitter

Glutamate,?GABA

Identifiers

MeSH

D017966

NeuroLex?ID

sao862606388

TH

H1.00.01.0.00044

FMA

84105

Anatomical terms of neuroanatomy

[edit on Wikidata]

Pyramidal cells, or?pyramidal neurons, are a type of?multipolar neuron?found in areas of the?brain?including the?cerebral cortex, the?hippocampus, and the?amygdala. Pyramidal neurons are the primary excitation units?of the mammalian?prefrontal cortex?and the?corticospinal tract. Pyramidal neurons are also one of two cell types where the?characteristic?sign,?Negri bodies, are found in?post-mortemrabies infection.[1]?Pyramidal neurons were first discovered and studied by?Santiago Ramón y Cajal.[2][3]?Since then, studies on pyramidal neurons have focused on topics ranging from?neuroplasticity?to?cognition.

Contents

·?1Structure

·?1.1Apical dendrite

·?1.2Basal dendrite

·?1.3Dendritic spines

·?2Growth and development

·?2.1Differentiation

·?2.2Early postnatal development

·?3signaling

·?3.1Firing classifications

·?4Function

·?4.1Corticospinal tract

·?4.2Cognition

·?5See also

·?6References

·?7External links

Structure[edit]

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Pyramidal neuron visualized by?green fluorescent protein(gfp)

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A hippocampal pyramidal cell

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One of the main structural features of the pyramidal neuron is the conic shaped?soma, or cell body, after which the neuron is named. Other key structural features of the pyramidal cell are a single?axon, a large?apical dendrite, multiple?basal dendrites, and the presence of?dendritic spines.[4]

Apical dendrite[edit]

The apical dendrite rises from the apex of the pyramidal cell's soma. The apical dendrite is a single, long, thick dendrite that branches several times as distance from the soma increases and extends towards the cortical surface.[4]

Basal dendrite[edit]

Basal dendrites arise from the base of the soma. The basal dendritic tree consists of three to five primary dendrites. As distance increases from the soma, the basal dendrites branch profusely.[4]

Pyramidal cells are among the largest neurons in the brain. Both in humans and rodents, pyramidal cell bodies (somas) average around 20?μm in length. Pyramidal dendrites typically range in diameter from half a micrometer to several micrometers. The length of a single dendrite is usually several hundred micrometers. Due to branching, the total dendritic length of a pyramidal cell may reach several centimeters. The pyramidal cell's axon is often even longer and extensively branched, reaching many centimeters in total length.

Dendritic spines[edit]

Dendritic spines?receive most of the excitatory impulses (EPSPs) that enter a pyramidal cell. Dendritic spines were first noted by Ramón y Cajal in 1888 by using?Golgi's method. Ramón y Cajal was also the first person to propose the physiological role of increasing the receptive surface area of the neuron. The greater the pyramidal cell's surface area, the greater the neuron's ability to process and integrate large amounts of information. Dendritic spines are absent on the soma, while the number increases away from it.[3]?The typical apical dendrite in a rat has at least 3,000 dendritic spines. The average human apical dendrite is approximately twice the length of a rat's, so the number of dendritic spines present on a human apical dendrite could be as high as 6,000.[5]

Growth and development[edit]

Differentiation[edit]

Pyramidal specification occurs during early development of the cerebrum.?Progenitor cells?are committed to the neuronal lineage in the subcortical proliferative?ventricular zone?(VZ) and the?subventricular zone?(SVZ). Immature pyramidal cells undergo migration to occupy the?cortical plate, where they further diversify.?Endocannabinoids?(eCBs) are one class of molecules that have been shown to direct pyramidal cell development and axonal pathfinding.[6]?Transcription factors?such as Ctip2 and Sox5 have been shown to contribute to the direction in which pyramidal neurons direct their axons.[7]

Early postnatal development[edit]

Pyramidal cells in rats have been shown to undergo many rapid changes during early?postnatal?life. between postnatal days 3 and 21, pyramidal cells have been shown to double in the size of the soma, increase in length of the apical dendrite by fivefold, and increase in basal dendrite length by thirteenfold. Other changes include the lowering of the membrane's?resting potential, reduction of membrane resistance, and an increase in the peak values of?action potentials.[8]

signaling[edit]

Like dendrites in most other neurons, the dendrites are generally the input areas of the neuron, while the axon is the neuron's output. Both axons and dendrites are highly branched. The large amount of branching allows the neuron to send and receive signals to and from many different neurons.

Pyramidal neurons, like other neurons, have numerous?voltage-gated ion channels. In pyramidal cells, there is an abundance of Na+, Ca2+, and K+?channels in the dendrites, and some channels in the soma. Ion channels within pyramidal cell dendrites have different properties from the same ion channel type within the pyramidal cell soma. Voltage-gated Ca2+?channels in pyramidal cell dendrites are activated by subthreshold?EPSPs?and by?back-propagating?action potentials. The extent of back-propagation of action potentials within pyramidal dendrites depends upon the K+?channels. K+?channels in pyramidal cell dendrites provide a mechanism for controlling the amplitude of action potentials.[9]

The ability of pyramidal neurons to integrate information depends on the number and distribution of the synaptic inputs they receive. A single pyramidal cell receives about 30,000 excitatory inputs and 1700 inhibitory (IPSPs) inputs. Excitatory (EPSPs) inputs terminate exclusively on the dendritic spines, while inhibitory (IPSPs) inputs terminate on dendritic shafts, the soma, and even the axon. Pyramidal neurons can be excited by the?neurotransmitter?glutamate,[4][10]?and inhibited by the neurotransmitter?GABA.[4]

Firing classifications[edit]

Pyramidal neurons have been classified into different subclasses based upon their firing responses to 400-1000 millisecond current pulses. These classification are RSad, RSna, and IB neurons.

RSad[edit]

RSad pyramidal neurons, or adapting regular?spiking neurons, fire with individual?action potentials?(APs), which are followed by a?hyperpolarizing?afterpotential. The afterpotential increases in duration which creates?spike frequency?adaptation?(SFA) in the neuron.[11]

RSna[edit]

RSna pyramidal neurons, or non-adapting regular spiking neurons, fire a train of action potentials after a pulse. These neurons show no signs of adaptation.[11]

IB[edit]

IB pyramidal neurons, or intrinsically bursting neurons, respond to?threshold?pulses with a burst of two to five rapid action potentials. IB pyramidal neurons show no adaptation.[11]

Function[edit]

Corticospinal tract[edit]

Pyramidal neurons are the primary neural cell type in the?corticospinal tract. Normal motor control depends on the development of connections between the axons in the corticospinal tract and the spinal cord. Pyramidal cell axons follow cues such as growth factors to make specific connections. With proper connections, pyramidal cells take part in the circuitry responsible for vision guided motor function.[12]

Cognition[edit]

Pyramidal neurons in the prefrontal cortex are implicated in cognitive ability. In mammals, the complexity of pyramidal cells increases from?posterior?to?anterior?brain regions. The degree of complexity of pyramidal neurons is likely linked to the cognitive capabilities of different anthropoid species. Pyramidal cells within the prefrontal cortex appear to be responsible for processing input from the primary auditory cortex, primary somatosensory cortex, and primary visual cortex, all of which process sensory modalities[citation needed]. These cells might also play a critical role in complex object recognition within the visual processing areas of the cortex.[2]

總結(jié)一下：大腦皮層中的pyramidal cell的apical dendrite向superfacial cortex生長(zhǎng)延伸，而不向下，basal dendrites在同層進(jìn)行延伸，而不向下，顯然basal dendrites的長(zhǎng)度和影響范圍要遠(yuǎn)大于apical dendrite。比如位于二、三層中的pyramidal cell應(yīng)該不會(huì)有dendrites延伸到五、六層，但是在二、三層中是同時(shí)有二、三層中pyramidal cell的所有dendrites和五、六層中pyramidal cell的apical dendrite，顯然二、三層中basal dendrites的占比要十分大。還有一個(gè)要點(diǎn)是，同一空間內(nèi)，會(huì)有很多pyramidal cell延伸的dendrites，這意味著某一空間點(diǎn)的信號(hào)輸入會(huì)導(dǎo)致周圍幾厘米的范圍內(nèi)很多神經(jīng)細(xì)胞的興奮，越遠(yuǎn)密度越小那種。