Spinal cord limb-control circuits receive abundant and diverse inputs that trigger and modulate limb movements (Lemon, 2008). Ultimately, however, we also want to understand the composition and function of spinal cord circuits in adult limbed vertebrates. For this and other reasons, many researchers have turned to studying spinal interneuron types and circuits in embryonic and early postnatal animals, which have fewer and simpler morphological types of interneurons that can often be identified by their early expression of combinations of particular transcription factors (Goulding, 2009 Grillner and Jessell, 2009 Kiehn, 2011). It has been difficult to delineate reliably morphological-physiological types of spinal cord interneurons in adult mammals (Jankowska, 1992, 2001 Jankowska and Edgley, 2010). In combination with T neuron physiological properties, these dendritic properties may help integrate supraspinal and propriospinal inputs and generate and/or modulate rhythmic limb movements.ĭefining neuronal types within the central nervous system is an important step to determine the composition and function of neuronal circuits. Thus, T neuron dendritic trees extend far mediolaterally, yet are unusually simple, which may help channel synaptic current from distal dendrites in the lateral and ventral funiculi to the soma. We found that T neurons have less total dendritic length, a greater proportion of dendritic length in primary dendrites, and dendrites that are oriented more mediolaterally. Here, we quantitatively investigated additional dendritic morphological characteristics of T neurons as compared to non-T neurons. These characteristics make T neurons good candidates to play an important role in integrating diverse inputs and generating or relaying rhythmic motor patterns. T neurons had higher peak firing rates and larger membrane potential oscillations during scratching than scratch-activated interneurons with different dendritic morphologies (“non-T” neurons). T neurons are multifunctional, as they were activated during both swimming and scratching motor patterns. T neurons were defined as having dendrites that extend further in the transverse plane than rostrocaudally and a soma that extends further mediolaterally than rostrocaudally. We previously described a class of spinal interneurons, called transverse interneurons (or T neurons), in adult turtles. Another possibility is that spinal interneurons that integrate inputs on distal dendrites have unusually simple dendritic trees that effectively funnel current to the soma. Active dendritic conductances may amplify distal dendritic inputs, but appear to play a minimal role during scratching, at least. These synaptic inputs can occur on distal dendrites and yet must remain effective at the soma. There are approximately 200,000 spines per cell, each of which serves as a postsynaptic process for individual presynaptic axons.Spinal interneurons can integrate diverse propriospinal and supraspinal inputs that trigger or modulate locomotion and other limb movements. Increased neural activity at spines increases their size and conduction which is thought to play a role in learning and memory formation. Appendages increase receptive properties of dendrites to isolate signal specificity. These dendrites do not process electrical signals.ĭendritic branching is also called "dendritic arborization" and "dendritic ramification."Ĭertain classes of dendrites contain small projections referred to as "appendages" or "spines". The long outgrowths on immune system dendritic cells are also called dendrites. Recent research has also found that dendrites can support action potentials and release neurotransmitters, a property that was originally believed to be specific to axons. Dendrites play a critical role in integrating these synaptic inputs and in determining the extent to which action potentials are produced by the neuron. Electrical stimulation is transmitted onto dendrites by upstream neurons via synapses which are located at various points throughout the dendritic tree. Freebase (0.00 / 0 votes) Rate this definition:ĭendrites are the branched projections of a neuron that act to conduct the electrochemical stimulation received from other neural cells to the cell body, or soma, of the neuron from which the dendrites project.
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