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An electrical synapse, or gap junction, is a mechanical and electrically conductive synapse, a functional junction between two neighboring neurons. The synapse is formed at a narrow gap between the pre- and postsynaptic neurons known as a gap junction .
Diagram of a chemical synaptic connection. In the nervous system, a synapse [1] is a structure that allows a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or a target effector cell. Synapses can be classified as either chemical or electrical, depending on the mechanism of signal transmission between neurons.
The main goal of electrical synapses is to synchronize electrical activity among populations of neurons. [3] The first electrical synapse was discovered in a crayfish nervous system. [3] Chemical synaptic transmission is the transfer of neurotransmitters or neuropeptides from a presynaptic axon to a postsynaptic dendrite. [3]
Some synapses dispense with the "middleman" of the neurotransmitter, and connect the presynaptic and postsynaptic cells together. [ac] When an action potential reaches such a synapse, the ionic currents flowing into the presynaptic cell can cross the barrier of the two cell membranes and enter the postsynaptic cell through pores known as connexons.
An electrical synapse is a gap junction that can transmit action potentials between neurons. Such synapses create bidirectional continuous-time electrical coupling [12] [13] between neurons. Connexon pairs act as generalized regulated gates for ions and smaller molecules between cells.
- Thousands of synapses on the dendrites - Active dendrites: cell recognizes hundreds of unique patterns - Co-activation of a set of synapses on a dendritic segment causes an NMDA spike and depolarization at the soma - Sources of input to the cell: Feedforward inputs that form synapses proximal to the soma and directly lead to action potentials
Synapses may be electrical or chemical. Electrical synapses make direct electrical connections between neurons, [41] but chemical synapses are much more common, and much more diverse in function. [42] At a chemical synapse, the cell that sends signals is called presynaptic, and the cell that receives signals is called postsynaptic.
In a parallel after-discharge circuit, a neuron inputs to several chains of neurons. Each chain is made up of a different number of neurons but their signals converge onto one output neuron. Each synapse in the circuit acts to delay the signal by about 0.5 msec, so that the more synapses there are, the longer is the delay to the output neuron.