![]() ![]() ![]() Possible source of neuromodulators and tissue factors.Possible contribution to memory: facilitation is possible due to plasticity of dendritic spines.Elementary integrative function: summation of excitatory + inhibitory potentials before the final current reaches the cell body.As the Ca 2+ channels operate in lower speed than the Na + channels, the transmitting signal travels along the dendrite with a different speed. At the peripheral branches, the Ca 2+ channels are more numerous, meanwhile the Na + channels are present at more distal segments. Voltage-Gated-Channels at the dendritic membrane are selectively permeable to either Na + or Ca 2+.These accumulations (hot-spots) may recover the declining membrane potential and dramatically increase the effectiveness of conductance: pseudo-saltatory transmission by dendritic spines.The most probable explanation is based on the presence of accumulations of the voltage-gated channels in various location of the dendritic membrane (at the heads and necks of the dendritic spines, at the dendritic branching points, and even at the whole dendritic segments). ![]() It appears more efficient than the mathematical models indicate. Measurements made in vivo suggest, that neuron's cable properties are not fixed quantities.The farther the origin of excitation from the soma (cell body), the greater the degree of the decrement until the current reaches the cell body.Therefore, the signal is conducted by electrotonic conduction: If a steady signal is applied to the end of a dendrite, the attenuation of the signal with distance will critically depend on the specific membrane resistance of the dendrite (the membrane potential will decline exponentially – decremental conduction). A dendrite may be considered to be an electrically leaky cable having a relatively low-resistance cytoplasm surrounded by a membrane consisting of resistive and capacitive elements in parallel.Thus they cannot propagate the action potentials. Because dendrites are long, narrow, branching structures, the synaptic signal produced in the dendrites is significantly attenuated (due to increased resistance) by the time it reaches the soma.The orientation of the dendritic tree determines the types and number of sources from which it can receive synaptic connections.The size of the dendritic tree limits how many synaptic inputs the neuron can receive.Enlarged surface area to receive signals from axons of other nerve cells:.There are also special dendritic organelles: dendritic spines, dendritic swellings.ĭendrite's Special Functions The dendrites contain dendritic organelles: neurofilaments, neurotubules, endoplasmic reticulum, mitochondria, ribosomes (metabolic autonomy). They have high variability in the branching pattern and extent (characteristic for individual neuronal types): different numbers of axonal contacts (up to approximately 100 000) and different types of contacts (axo-shaft, axo-spine, dendro-dendritic). Dendrites (in Greek it means "tree") are branched protrusions from the neuron's soma that transmit post-synaptic potentials to it. ![]()
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