# Ion channels and synaptic transmission

## The synapse

### Electrical and chemical synapses

In order to be able to pass signals from one nerve cell to the next or to a muscle cell, certain transmission processes are required. The contact points at which the transmission takes place are specialized structures and are called synapses. We now know that there are also electrical synapses in addition to chemical synapses. Chemical synapses, on the other hand, show a very variable spectrum of signal transmission and can thus cause complex changes.

Tab. 1
Differences between electrical and chemical synapses
Synapse typedistanceCytoplasmic connectionUltrastructural componentstransmissionSynaptic delaydirection
electric3.5 nmYesGap junctionsIon currentpractically nonetypically bidirectional
chemically20-40 nmnopresynaptic vesicles, active zones, postsynaptic receptorschemical transmitterstypically 1-5 $ms$unidirectional

(Table based on: Kandel et al., 2000)

## Literature

Kandel, E. R .; Schwartz, J. H .; Jessell, T. M. (2000):Principles of Neural Science. McGraw-Hill, ISBN: 0838577016