Syaptic Potentials amp; Cellular Isyaptic电位amp；细胞我.docVIP

-80- Synaptic Potentials Cellular Integration Graphics are used with permission of : (/) Benjamin/Cummings Publishing Co (/bc) Page 1. Introduction ? Synaptic potentials are the incoming signals to the neuron. ? When the neuron is depolarized to threshold, it generates an action potential. ? The action potential is the outgoing signal of the neuron. Page 2. Goals ? To review the characteristics of the action potential. ? To learn that synaptic potentials are small, variable in amplitude, and decay with distance. ? To understand that synaptic potentials summate. ? To know the difference between temporal and spatial summation. Page 3. Review of the Action Potential ? Recall that action potentials are all-or-none events. ? For a given cell, the action potential has the same amplitude and duration as it travels along the axon. ? Because the action potential is always the same, it is the signature of the cell. ? The action potential can travel for long distances because it does not decay and is regenerated continuously as it moves along the axon. Page 4. Synaptic Potentials are Small ? Synaptic potentials are considerably smaller than action potentials. ? Excitatory postsynaptic potentials depolarize neurons. -81- ? Inhibitory postsynaptic potentials depolarize neurons. * Now is a good time to go to quiz question 1: ? Click the Quiz button on the left side of the screen. ? Work through quiz question 1. ? When you are done return to Page 5. Synaptic Potentials Vary in Amplitude. Page 5. Synaptic Potentials Vary in Amplitude ? The amplitude of a synaptic potential varies and is related to the number of synaptic vesicles releasing neurotransmitter. ? The number of vesicles releasing neurotransmitter in turn is related to the amount of calcium that enters the presynaptic terminal. ? In some neurons, rapid firing of action potentials allows more calcium to enter the terminal. This causes enhanced postsynaptic potentials, or potentiation, for a pe