Synapse cellular signaling

Two specialties of the nervous system are speed and localization, accompHshed using highly developed electrical signaling and close cellular apposition. At specialized points of communication, such as the synapse and the neuromuscular junction, the cells are separated by a nanometer or less. 

To illustrate the action of ion channels in cell-to-cell signaling, we describe the mechanisms by which a neuron passes a signal along its length and across a synapse to the next neuron (or to a myocyte) in a cellular circuit, using acetylcholine as the neurotransmitter. 

The third dimension of chemical neurotransmission is function, namely that cascade of molecular and cellular events set into action by the chemical signaling process. First come the presynaptic and then the postsynaptic events. An electrical impulse in the first, or presynaptic, neuron is converted into a chemical signal at the synapse by a process known as excitation-secretion coupling. 

The fundamental cellular component of the nervous system, the neuron, has long, branching, cyllndrlc processes (dendrites and axon) that extend from the cell body. Dendrites are modified for signal reception and transduction and form extensive networks that permit Interneuronal communication, coordination, and integration of nervous-system function. The axon typically is a long extension of Che neuron specialized for transmission of electric signals and, at Its distal end, for chemical communication of Information to other neurons or to muscle at sites termed synapses and neuromuscular junctions, respectively. 

Nerve cells (neurons) are specialized so that at one end there is a flared stracture termed the dendrite. At the dendrite, the neuron is able to process chemical signals from other neurons and endocrine hormones. H the signals received at the dendrite end of the neuron are of a sufficient strength, and priperly timed, they are transformed into action potentials that sweep down the neural cell body (axon) frc n the dendrite end to the other end of the neuron, the presynaptic portion of the axon that ends at the next synapse (the extra cellular gap between neurons)in the neural pathway. The arrival of the action potential at the pre aptic terminus causes the release of ions and chemicals (neurotrananitters) that travel... 

Besides regulatory effects on signalling through cellular cytokine and growth factor receptors, adhesion processes are controlled by the individual /V-glycan content of particular adhesion molecules. A critical step in cellular invasiveness is the fine-tuned regulation of cell adhesion to the extracellular matrix, executed by focal cell adhesion synapses (focal adhesion complexes) that are regulated by the focal adhesion kinase... 

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