EPSP's and IPSP's

Postsynaptic Potentials

• graded potentials

• strength determiend by:
  - amount of neurotransmitters released
  - more ntm, longer duration of ntm present in synaptic cleft, the greater the magnitude of the graded potential
  - time the neurotransitters is in the area

• Types of postsynaptic potentials:
  1. EPSP- excitatory postsynaptic potentials
  2. IPSP- inhibatory post synaptic potential

• some of the EPSP’s and IPSP’s that determine the outcome

• if you have single EPSP or IPSP there will only be subtle change in membrane potential, if you have multiple EPSP’s or IPSP’s close in time succession you will have greater change in membrane potential

Excitatory synapses and EPSP’s

• excitatory because we have a depolarizing stimulus
  - moving closer to zero, membrane potential is becoming less negative

• depolarizing = EPSP

• EPSP: when ntm binds to receptor causing a deep polarizing change in membrane potential

Inhibatory Synapses and IPSP

• hyperpolarizing signals

• ntm binds through receptor and membrane potential becomes more negative

• moving away from zero

• hyperpolarizing: harder to reach threshold and stimulate action potential
  - used to decrease or prevent liklihood a nueron can generate action potnetial

Integration: summation: scenario where there is so much time in between EPSP that it has time to go back to resting potential

• integrating incoming integration

• neurons: filter out information or integrate information

• if you have excitatory signal you will cause EPSP
  - if you wait a while you get another EPSP and another excitaory signal

• magnitude of EPSP will be very small, since they are so far apart and do not help eachother, they are not additive, no summation, so nothing happens

Temporal Summation

• Integration: summation: neuron fires twice, close together

• singnals fire close together, second excitatory signal occurs before the first one can get back to resting
  - first signal with second signal so close together make the signal much stronger, greater change of membrane potential (summation- additive acceft of multiple graded potnetials that occur close enough in time, temporal which is what this is)

• temporal is time, only require one presynaptic neuron for temporal summation

• about how quickly the presynaptic neuron fires in time

Spatial Summation

• Integration: Summation: two presynaptic neurons

• the presynaptic nuerons form independent synapses

• when the two presynaptic nuerons fire are identical times, there is a greater change in membrane potential than of either one fired alone

• example of spatial summation because the synapses are not combined but when fired at same time is greater then alone

• requires minumum of two presynaptic neurons all synapsing onto the same post synaptic neuron

• can have excitatory spatial summation, inhibatory spatial summation, or causing neutral event

Spatial summation of EPSP’s and IPSP’s

• one excitatory presynaptic neuron and one inhibitory presynpatic neuron

• if inhibatory nueron fired: there would be hyperpolarizing change
  - results in decrease in. membrane potential away from zero

• what if one excitatory presynaptic neuron and one inhibitory presynpatic neuron fired at the same time?
  - they would cancel eachother out and there would be nothing
  - example of spatial summation

• not garunteed to reach threshold since you can have both EPSP’s and IPSP’s, they can both summit and nothing happens