What happens when APs reach presyntaptic terminals?

  -  Intensity is signaled by frequency

  - High-frequency results in summation

  of the pre- and post-synaptic signals

  - So... synaptic transmission is

  amplitude modulated

Comparison of chemical and electrical synapses

  coupled cells, through channels formed by connexin proteins

  (unlike at chemical synapses)

  -Fast, but complex integration cannot

     occur

   of positive and negative, fast and

   slow signals

PSPs mediated by metabotropic receptors and by channel closing 

-closing tend to be slower than those mediated by ionotropic receptors and channel opening

In the CNS, post-synaptic potentials are generally ineffective singly

-because they are small (0.1–1.0 mV), unlike endplate potentials, which are normally effective singly.

-Moreover, PSPs are mostly generated far from the trigger zone and they to decrement significantly during propagation

 -The safety factor for AP initiation in response to a single EPSP consequently tends to be far less than 1

 -The effectiveness of PSPs therefore depends upon passive membrane properties, temporal and spatial summation