Temporal Summation

• Excitatory postsynaptic potential (EPSP)


  Graded depolarization resulting from a flow of sodium ions into the neuron
• Inhibitory postsynaptic potential (IPSP)


  Temporary hyperpolarization of a postsynaptic cell
• Spatial summation


  Summation over space. Several synaptic inputs originating from separate locations exerting a cumulative effect on a postsynaptic neuron
• Presynaptic neuron


  Neuron that delivers transmission
• Sherrington referred to this phenomenon as temporal summation
• EPSP’s magnitude

  Decreases as it moves along the membrane
• Graded potential


  Either depolarization (excitatory) or hyperpolarization (inhibitory) of the postsynaptic neuron
• IPSP occurs when

  K+ leaves the cell or Cl- enters the cell after it is stimulated
• EPSPs are not action potentials
• Postsynaptic neuron


  Neuron that receives transmission
• Sherrington found that repeated stimuli within a brief time have a cumulative effect