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At the neuromuscular junction, presynaptic motor axons terminate 30 nanometers from the cell membrane or sarcolemma of a muscle fiber. The sarcolemma at the junction has invaginations called postjunctional folds, which increase its surface area facing the synaptic cleft. [4]
The fusion of a vesicle is a stochastic process, leading to frequent failure of synaptic transmission at the very small synapses that are typical for the central nervous system. Large chemical synapses (e.g. the neuromuscular junction), on the other hand, have a synaptic release probability, in effect, of 1.
Axon terminals (also called terminal boutons, synaptic boutons, end-feet, or presynaptic terminals) are distal terminations of the branches of an axon. An axon, also called a nerve fiber, is a long, slender projection of a nerve cell that conducts electrical impulses called action potentials away from the neuron's cell body to transmit those ...
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.
Chemical synaptic transmission is the transfer of neurotransmitters or neuropeptides from a presynaptic axon to a postsynaptic dendrite. [3] Unlike an electrical synapse, the chemical synapses are separated by a space called the synaptic cleft, typically measured between 15 and 25 nm. Transmission of an excitatory signal involves several steps ...
Motor neurons, which is the common inhibitor in crab limb closers and limb accessory flexors, form axo-axonic synapses in addition to the neuromuscular junction with the muscles in crayfish. [46] These synapses were first observed in 1967, [6] when they were found to cause presynaptic inhibition in leg muscles of crayfish and crabs. Subsequent ...
It is an enzyme that catalyzes the breakdown of acetylcholine and some other choline esters that function as neurotransmitters: acetylcholine + H 2 O = choline + acetate. It is found at mainly neuromuscular junctions and in chemical synapses of the cholinergic type, where its activity serves to terminate cholinergic synaptic transmission.
The neuromuscular junction (NMJ) is the most well-characterized synapse in that it provides a simple and accessible structure that allows for easy manipulation and observation. The synapse itself is composed of three cells: the motor neuron , the myofiber , and the Schwann cell .