| Popis: |
The extracellular ionic environment of excitable tissues plays an important role in the regulation of their activity. Some of the processes influenced by external ions include transmitter release at synaptic junctions, coupling between excitation and contraction of muscle, coupling between excitation and secretion in endocrine and exocrine cells, membrane excitability, and several metabolic processes. In the past, the ionic milieu of the nervous system has often been assumed to be relatively fixed in its composition. Experiments in recent years, however, indicate that nervous activity can alter the ionic environment in the vicinity of nerve cells, their processes, and surrounding structures. The effect of nervous activity on the extracellular ionic environment is primarily to alter the concentrations of two ions - potassium and calcium. In this article, Sol Erulkar and Forrest Weight consider the influence of these extracellular ionic alterations in modulating the release of neurotransmitter from nerve terminals. |
