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George E. Carvell, PhD, PT   University of Pittsburgh
LOCAL POTENTIALS VII: Inhibitory Control 1 “Life is hard enough, your will should not be preoccupied with calming an endless storm of electrochemical chaos” GEC ‘01
BC&P Fig 5.20  p. 125
LEGEND:Fig 5.20 “Shunting inhibition. A neuron receiving one excitatory and one inhibitory input. (a) Stimulation of the excitatory input causes inward postsynaptic current that spreads to the soma, where it can be recorded as an EPSP. (b) When the inhibitory and excitatory inputs are stimulated together, the depolarizing current leaks out before it reaches the soma.” p 125
Fig. 12-16 p.226
Inhibitory synapses have a key role in controlling levels of neuronal excitability. Inhibitory synapses are located along dendritic shafts (especially at branch points), are axosomatic (directly on soma) and are even found at the axon hillock. Thus, inhibitory synapses are in a key position to counteract the depolarizing influences of excitatory synapses on dendrites and dendritic spines. Active Inhibitory Synapses cancel all but the most potent excitatory inputs.
Axosomatic Inhibitory
Synapse reduces size of EPSP
Axodendritic Inhibitory
Synapse shunts EPSP