Excitatory postsynaptic potential

The Excitatory ( causing) postsynaptic potential ( EPSP) ( Sheet excitatory postsynaptic potential) is a local, gradual change in the membrane potential of the postsynaptic membrane of nerve cells, which triggers an action potential in the postsynaptic element or contributing to the release.

The potential is caused by the release of a certain amount of an excitatory neurotransmitter, and the activation transmitter gated ion channels, which are usually at the same time permeable to sodium and potassium ions.

In general, these local and graded potentials depolarize the postsynaptic membrane. For intracellular dissipation of the membrane potential, the EPSP is as depolarization of the Somamembran as a result of passive diffusion and the summation of potentials represents the size of the EPSP is dependent not only on the amount of released transmitter, but also on the previous size of the membrane potential.

Increases, for example, experimentally induced (first ) membrane depolarization the EPSP is smaller, i.e., the membrane resting potential from their already depolarized, the amplitude of the excitatory postsynaptic potential increases and eventually becomes smaller Vordepolarisation equal to zero ( the reversal potential for the excitatory potentials is reached). Upon further Vordepolarisation a potential is reached with the opposite sign.

The EPSP is therefore not always a depolarization, but drives down the membrane to a specific equilibrium potential which is usually far below the resting potential. The thereby acting ion mechanism is of a complex nature. Beside the EPSP, wherein increased conductivity membrane ( membrane permeability ) observed for sodium and potassium ions are also those in front of reduced conductivity. Here it is assumed that the triggering mechanism is the closure of " leaky " (English leakage) channels for potassium ions.