1. Post-Synaptic Events Graded vs Action Potentials
Excitatory vs. Inhibitory PSPs
Pre- vs. Post-Synaptic Inhibition
Divergence vs. Convergence

3. One synapse is generally not sufficient to
generate a threshold stimulus at the axonal
hillock.
Most neurons receive thousands of synaptic endings -
each of which contributes a postsynaptic potential
(EPSP or IPSP) of less than 1 mV.
Each of these PSPs are conducted to the axonal
hillock with decrement (decay).
An action potential will only be generated if the
sum of the IPSPs and EPSPs reaching the axonal
hillock at any time exceed the threshold voltage.

4. Dendrite of
postsynaptic
neuron
Axon terminals
of presynaptic
neuron
Dendrite of
postsynaptic
neuron
Glial cell
processes
Axon

5. Spatial
summation

8. excitatory inhibitory A D E B C electrode threshold A A+B A+B+C D D+E
A+B+C+E

9. Postsynaptic Inhibition

10. Presynaptic Inhibition

11. Divergent
circuit
Allows for
amplification
of a signal:

12. single pyramidal cell in the motor cortex of the brain
15-20 internuncial cells in CNS
each stimulates several hundred motoneurons
each of these stimulates muscle fibers
Divergence results in 50,000-fold amplification

13. Important for summing, correlating and sorting information in the CNS
Convergent circuit
Important
for
summing,
correlating
and sorting
information
in the CNS