What is summation in action potential


Synonym: synaptic integration

1 definition

Under Summation one understands the temporal or spatial calculation of excitatory (EPSP) and inhibitory synaptic potentials (IPSP) on a neuron. If the sum of the EPSPs exceeds a threshold value, an action potential is triggered on the axon hill.

2 physiology

Every nerve cell receives a multitude of signals through adjacent synapses. The stimulus of a single EPSP only leads to a slight local depolarization of the membrane of less than 1 mV. Exciting potentials must arrive via numerous synapses or close behind one another in order to exceed the threshold value for an action potential. The spatial distance to the axon hillock also plays a role here. Inhibiting synapses can greatly reduce these potentials through hyperpolarization and stabilize the resting potential. They usually have a disproportionately stronger effect, as they often lie directly on the soma of the neuron.[1][2]

2.1 Spatial summation

The potentials created by different synapses add up and spread electrotonically in the cell.

2.2 Temporal summation

Several potentials of a synapse add up over time. EPSPs usually have a duration of 5-20 ms. If a second EPSP arrives during this period, its amplitude is added to the sum of its individual amplitudes.

3 source

  1. ^ Josef Dudel: Neuroscience. Spriner, 2nd edition, pp. 138-140.
  2. ^ Etherington, Sarah J, Atkinson, Susan E, Stuart, Greg J, and Williams, Stephen R (May 2010) Synaptic Integration. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002 / 9780470015902.a0000208.pub2]