Читать книгу Neurobiology For Dummies - Frank Amthor - Страница 106

Earlier in this chapter, I explain that ion channels can be gated either by ligands (neurotransmitters) or voltage. Gating changes the channel’s state from closed to open, or vice versa. Gated channels are at the core of how neurons integrate and process inputs, and how they communicate with other neurons (or, as neurobiologists always say, “No neuron is an island”). Neurons receive messages in the form of neurotransmitters through ligand-gated channels on their dendrites, soma, and, in some cases, axon. These inputs are excitatory if the receptors flux sodium ions, inhibitory if they flux potassium or chloride.

Opening channels changes the voltage across the neurons membrane by the flow of ions. We use the Goldman–Hodgkin–Katz equation to calculate the membrane potential that results. If the neuronal membrane potential becomes sufficiently less negative (depolarized), the effect may be to open voltage-gated ion channels. Two of the most important voltage-gated ion channels are those of the sodium and potassium channels that lead to the action potential, an all-or-nothing spike of voltage that serves as the basic unit of electrical signaling in neurons.