Synapse
The gap between neurons where communication occurs.
Properties of a synapse
Discovered by Sherrington:
1. Conduction of a message is slower in a reflex arc (15 m/s) vs along an axon (40m/s)
2. Several weak stimuli at similar locations/times produce a stronger reflex than one stimulus alone
3. When one set of muscles becomes excited a different set relaxes
Reflex arc
The circuit of communication from sensory neuron to muscle response
Temporal Summation
Repeated signals over time add up to trigger a neuron.
(eg. one pinch won’t produce a response, but multiple over time will add it’s effect until it exceeds the threshold of the postsynaptic neuron, producing an action potential)
Spatial Summation
Signals from different places combine to trigger a neuron.
(eg. pinching two separate locations at the same time will create a response as the axons converge into one neuron in the spinal cord)
Inhibitory Postsynaptic Potential (IPSP)
When a message is sent to excite one area, other areas may be inhibited.
Potassium/Chloride gates open.
It can’t travel far like an action potential, instead it gets weaker the more it spreads, and then disappears.
Spontaneous Firing Rate
Most neurons have a periodic production of action potentials even without synaptic input
Excitatory Postsynaptic Potential (EPSP)
Results from a flow of sodium ions into the neuron. If EPSP does not cause the cell to reach its threshold, the depolarization decays quickly
Tempora Summation
Repeated stimuli within a brief time has a cumulative effect
Presynaptic Neuron
The neuron the delivers transmission
Postsynaptic Neuron
The Neuron that receives the transmission
Spatial Summation
Synaptic inputs from seperate locations combine their effects on a neuron
Synaptic Cleft
the space between the presynaptic and postsynaptic neurons
