APK 2105C Lecture Notes - Lecture 29: Choline, Muscarinic Acetylcholine Receptor, Skeletal Muscle

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Chapter 8, Lecture 2
Synaptic Transmission
Excitatory synapses
o Excitatory post-synaptic potentials (EPSP) bring Vm closer to threshold
depolarization
May allow Na and K to flow through
K flows out
o K has chemical driving force out of cell
o K has electrical driving force to stay in the cell
Why it moves slows than Na
Na flows in
o Higher force of this happening than K flowing out
Na has higher driving force into the cell
Na has electrical driving force into the cell
Causes depolarization
o Closure of K channels acts to depolarize a cell by preventing cations from leaving
the cells
Adenylate cyclase uses ATP to make a 2nd messenger
Accumulate K inside the cell
Inhibitory synapses
o Hyperpolarization or Vm stabilization
o K or Cl movement
Open K channels
K leaves
Cell gets more negative
Open Cl channels
Higher conc outside the cell
Brings Cl into cell
Makes cell more negative
o Inhibitory post-synaptic potentials (IPSP) move the Vm further from the
thresholdhyperpolarization
Harder to generate AP
Neural integration
o One synapse alone doesn’t determine whether an
AP will result
Very unlikely that one synapse will
generate enough for AP
o An AP is triggered if the Vm is depolarized to
threshold at the axon hillock
Summation is necessary
o Typically have more of these systems
o May go to multiple axons throughout the body =
divergence
o May converge onto one neuron = convergence
Temporal and spatial summation
o Have to sum up all the synapses to get to threshold for AP
o Separately they will not give enough to get to threshold
o EPSP and IPSP will be lower by the time it gets to the axon hillock
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