Repeated stimuli within a brief time have a cumulative effect.

Synaptic inputs from separate locations combine their effects on a neuron.

Observed several properties of reflexes suggesting that there are junctions between neurons:

1. Reflexes are slower than conduction along an axon (synapses must exist)

2. Several weak stimuli presented at slightly different times produced a stronger reflex than a single stimulus (summation)

3. When one set of muscles becomes excited, another set relaxes. (inhibitory synapses)

Ordinarily occur together. A neuron may get both the summations, and then integrates the inputs. Ex. neuron in visual system could respond to light moving in one direction, but not the other. (order, location, frequency of inputs all matter)

Interneurons can send a message to block activity of certain postsynaptic cells. Ex. flexing biceps causes triceps to relax.

These inhibitory synapses hyperpolarizes the postsynaptic cell.

K+ gates open, causing K+ to rushout, further decreasing the probability of action potential.

Temp hyperpolarization called IPSP

Spontaneous firing rate: most neurons spontaneously fire, and EPSP/IPSP increase/decrease that rate.